Psych11F Study Guide Final
Psych11F Study Guide Final Psychology 119F
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This 321 page Study Guide was uploaded by Marissa Mayeda on Sunday March 15, 2015. The Study Guide belongs to Psychology 119F at University of California - Los Angeles taught by Blair in Winter2015. Since its upload, it has received 398 views. For similar materials see Neural Basis of Behavior in Psychlogy at University of California - Los Angeles.
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Mapping ITD onto spatial locations 0 lTDs are measured in microsecondc p5 because the difference in a sound s arrival time at the two ears is very small mpJwwwnwip speciesrTymralbarLjpg 9039 5039 3039 0 30 5039 90 Left 4 AZIMUTH Right Right 4 AZIMUTH gt Left Exmmal nuclzus Inferior colliculus an Lateral ShelI of cemml nucieus Huhit r r Inferior colhculus 39 Core of central nucleus Inferior colllculus Anterior lmeral 1 lemniscol nucleus Posterior Imam I lemnlscal nucleus T Nucleusangulans l Nucleus mognoceumans Mm Inner ear Delay lines can convert a time code to a quotplacequot code Jeffress Model Rightinput ti Left NM Assume neurons AE are NL neurons and each receives input from NM neurons in the left amp right hemisphere The delay from each L or R input is different for each NL neuron so that each cell prefers a different ITD The sound s location determines when NM neurons will fire time code The sound s location determines which NL neurons will fire place code Does the mammalian brain work the same way Mammals can localize sounds too but not as well as owls Do they also have Jeffress delay lines in their brains Predator hears where prey is locatedand prey hears where the predator is coming from httpwwwnalurewmnaturEloumalwu7n6336images41732227f12jpg Mammalian ITD detector circuitry In mammals ITD detection occurs in a brainstem nucleus called the medial superior olive M50 which receives bilateral excitatory input from the ventral cochlear nucleus VCN Therefore MSO may be regarded as homologous with ML and VCN may be regarded as homologous with NM VCN contains two types of frequency tuned phaselocking neurons spherical bushy cells I SBCs and globular bushy cells SBCs But only L lfit CN I the SBCs project to the MSOso where do the 39 GBCs project to GM 3 I I I GBC I I I I nght VCN J Mammalian ITD detector circuitry GBC neurons send bilateral excitatory projections to the nucleus of the trapezoid My NTB The ipsilateral projection targets the lateral NTB and the contralateral projection targets the medial NTB The GBC synapse onto medial NTB neurons is a highly specialized synapse called the Calyx of Held Left Ear Right Ear i I LeftMSO gtlt Right M50 t P P 4 SEC GBC GBC nght VCN I r Calyxol Held Largest synapse in mammalian brain Faslesl and most reliable WW alwalCa lyx of H e d lire alter 1 ersde rar belore cont laieral laieralea The Caryx39ofuweld Is the largest fastest an r most reliable synapse In le entire mammalian brain Many synapses in the central nervous system are quite unreliable for example cortical glutamate boutons often have only 10 chance of releasing glutamate on each presynaptic action potentials The Calyx of Held is 100 reliable and always fires the postsynaptic MNTB neurons with every action potential MNTE puma ca mml mm mum mm ul Hm cam am Nllme Revlcwsl Neulasmerlee Feedforward inhibition from NTB LNTB neurons convey feedforward inhibitory inputs from the ipsilateral ear to MSO MNTB neurons convey feedforward inhbitory inputs from the contralateral ear to M50 The inhibitory neurotransmitter used at these synapses is glycine Left Ear Feed Forward lnhibilion Ear Right ear inhibits and excites same area SBC GBC I I GBC I ILeftVCN J nght VCN Inhibitory I I l l i gt Excitatory RES39JLNIE Contralateral inhibitory input 2 3 D Summed EPSP amp IPSP is a I precedes excitatory input WWWt biphasic PSP inh then exc Ipsilateral excitatory input V Ex 95 Summed EPSP amp lPSP is a precedes eeitater y input quot5 V monophasic P5P exc only inhibitory V TOTAL Summe r full and contra solid line is sum cfdottedlinet inpur n rln a biphasic 35 E at zero ITD N G 1 ms MSO essentially receives four inputs an ipsilatera excitatory and inhibitory input and a conha eral excitatory and inhibitory input The Calyx of held is so fast that the contralateral inhibition is the FIRST input to arrive in M50 even though it travels the farthest At zero ITI the two excitatory inputs are about simultaneous Ipsi ear lags Contra ear lags V I CONTRA CONTRA 1K CONTRA rest Vi shift Rs V 4 lPSl IPSI WSl rest r V V TOTAL A TOTAL V f big rm best sounds lrom ipsulaeral cell do lie way out cl alignment no ld lrom xps l5 best psi When the sound in one ear is delayed Ear both the EPSP and IPSP from that ear are shifted in time together Hence the effect is to shift the summed ipsilateral and summed contralateral PSPs against each other in time This causes the M50 neuron to produce a graded response that is maximal when the ipsi ear lags medium at zero ITD and minimal when the contra ear lags am neurons pveler am nme derays urn neuron encode each whore range or ITDs owl expenencaBam owl 9055 TD EXPE spalse code quotN 255 a rn c but in ow u is turned mm a place code and in Mammal all nus happens at canain Irequeney EXPER ENCED b quot quot9 quot739 5 7 RA GE rer ITD prelerence greater than mouse W quot EVE hear due Io size 0 me nsadr never near ads I rm n39 e quotuskecause nead Is r nl mammr i Mun mm a best ITD r sound come mm rnrddle differs by neurons that pveiel 2m and neurons that preler 7200 me exacuy he same rare code or dismbmed cnde fre uenc preference 3 ITD us am neurons prever sounds horn dru sources x r a r 500 03 Right car leading penered rm curves Sparse I Code praee code which nnng mosr precer neg ilds on his side 100 5 lmng comparalrvelm F I 39 I I I I I l I r I r I 100 4 J 439 J rt0 9 Right car leading I Left ear loading ITD Lus aH neurons rn mso preler same 200 S 053 nu ongm on comrarareral srde 1oo us Mr r Distributed rare code de don39t know comra aleral are me 33388 M if an ure equally sound rs in me mrddle 200 5 39 V rate codeh ow MUCH more some neurons Irnng than omers Auditory Localization Insects wipositor Crickets The common field cricket gryllus assimilis is a member of the insect order Orthoptera which also includes grasshoppers amp katydids All members of rthoptera members have large hindlegs for jumping lemale crickets must be able to localize sound Female crickets have a long ovipositor used for laying their eggs after mating Male crickets have specialized wings used for singing to attract females Phonotaxis by female crickets Phonotaxis is defined as movement taxis that is directed by sound phone Speaker 1 Speaker 2 different species same species able to go to the speaker at her own species Experimental Demonstration by Manfred Hartbauer 0 Cricket Song Male crickets produce their song by rubbing their wings together a behavior called m The chirping frequency varies with temperature You can use a cricket as a thermometer by counting the number of chirps in 15 seconds and adding 37 to estimate the temperature in degrees Farenheit The singing response can be triggered by a variety of different stimuli Aggressive song may be elicited by a male competitor Alarm song may be elicited by a predator to warn other cric ets Courtship song is triggered by an internal stimulus the desire to mate mm mu Z Song Production The cricket s forewing is called the tegmen It is a transducer that converts mechanical energy into sound energy One wing is called the E and it is lined with a series of teeth The other wing is called the scraper or glectrum and it runs across the teeth to generate the cricket s song Syllables of the Cricket s Song A syllable is a single sound pulse produced by a single closing of the wings lakes aoms ior wings to close once The carrier freguency is the rate in Hz at which the scraper strikes each successive tooth of the file spikes per second 139 le gammyw 3 HO39J EWW r mimll rill ill ml 39ulv vim ni39n iulltlz il m m Chirps trills and sequences 39 Am is a series of syllables in rapid succession separated from other chirps by a pause The syllable repetition rate is the rate of syllable Gym generation in Hz during the chirp PM W ll 39i 1 J y Atril is a very long chirp 39i uninterrupted by a pause lmmririinq Wm win A seguence is a repeated pattern of chirps and trills occurring in a particular order Carrier Frequency has pauses o zHow cnckels to open and dose wmgs Simulated Cricket Song 4 kHz 5 kHz OHZ Q Q Tone ab e o IOCEIIZE sound at Denim Hz requency Syllable Repetition Rate 33 HZ 33 Hz 22 Hz 9 w w w a 4n Trilling Chiming At 25 Hz Auditory localization She obeys a very simple rule Turn toward the sound and walk But how does she know which direction the sound is coming from 39ia We I I a Po x Q 7 1 J r v0 I I l lnlra roll camera Avmlspeaker The Insect Treadmill The direction and speed of an insect s walking behavior can be measured using a clever device called an insect treadmill The insect is placed on top of a very lightweight ball which rotates beneath the animal s feet whenever it walks so that the insect remains centered on top of the ball The rotation of the ball is measured as the animal walks to record the speed and direction of walking Why 0 why dear fly Mason AC Oshinsky Ml Hay 242001 Nature 41068690 When the ormia fly is on the treadmill the cricket song doesn39t just stimulate the fly to walkinthe fly walks TOWARD the sound of the cricket Fly walks forward when speaker is in front of the treadmill Fly walks right when speaker is to the right Fly walks left when speaker is to the left eh nigh OVERHEAD VIEW OF TREADMILL circle AND RECONSTRUCTED WALKING PATHS lines mm Ih5 ggphl tDmLXEJnaLUU4BVSBGEGIszJAAAAAAAAVDEycluEivlui simpeimumnihumb ipg imgmax io When the female ormia fly reaches the male cricket she mounts him and inserts a needlelike ovipositor into his abdomen then injects her fertilized eggs into his body A few days later the male cricket is dead and he becomes food for the ormia fly larvae to feed on as they grow into adults mmWeVolutianherkelevaduevoiihreWimagssnawScrickeLparasmzedwg Ormia fly s hearing organ SIDE VIEW a lrom sound The ormia fly s hearing organ is located on the front of its thorax just behind its quotchinquot localize sound source and perform phonoiaxi The henmg orga39r L39SlStS ofa tym39 r um eardrum on L cv side numhered 1 amp 2 j39 J together at the r me by a flexible hinge czllt 391 the intertymganal pridge numbered 3 The larr and right tympani are only about 05 mm apar H39w long would it take for a sound to travel this df r nce ITD 90quot 15 can t measure this omerence The intertympanal bridge physical couples the left and right tympani together so that oscillations of one tympanum can affect oscillations of the other strength of couplmg allect how much second eardrum vibrates Interaural latency difference in neural responses Neural recordings of field potentials can be made from the fly s auditory nerve on one side either left or right g39masb gas hquotsgeadwe39 s When the speaker is positioned at i90 azimuth the response in the nerve contralateral to the speaker is delayed by N100 us with respect to the response in the nerve ipsilateral to the speaker This intgraural resporse difference is ove 6 X larger t a the ITD of 15 m Ipsilaleral i 51m WV 39139 39 nolfl 39u gl 39ar ix ee n w as a mouse s ea latency difference very large 09 Latency difference uls lel The intertympan I rise constrains tL C At mm and right tympar I almost always 5 illate in quot5 either bendquotg rocking mode a 394 only ve 39u m lTDlessm rarely in mediate mode w laquot lTDU39 39M39 9 bend al same lime Fulcrum Bending mode is an 39 phase oscillation 0quot quot 39 39 quot quot 39 quot39 39 phase omen Without rigid comedian weak copuling Bendlng mode I A Rocking mode is anti phase oscillation 180 phase of set Rocking rlgld connectlon strong coupling two waves out oi phase mode 2 A Intermediate mode is midphase oscillation V V V V V 7 Intermediate other phase offsets A mOdO 1 2 httpnelsonbeckmanillinDiseducoursesneuroe quot0 WW 391 0 Phase 0 i Phase holmadalSflyhearingpreslemumjampg A 1 A l 39 A m a VlvwIs The inter m anal bnd e a stiff y p 9 1 v gn Medium 0 3 V 8 E on i 39 39 e g n m mending gt q L n I gt A E g j a 0 d 39 p 3 I o l a 3 an o u 3 Ft F39Wh e me Fit c CL 131 39 39 rocking EJ ED 30 90 V AZImulh ill 05 s Fumm period ol 5 Khz one Is 200ps comparable o ITD oi owl wlial iine arrive at one place or another V e A at 5H2 atwhat point does one ear Response of the two tympanlqtili S Wflll C vbvaie m cricket carrier freq depends upon how stiffly they are coupled by the Bending A 9 quotquot R5d0 1 intertympanal bridge Stiff coupling A permits only the rocking mode Sof t mode 2 couping permits only the bending ummgwhen one upov A down is W Dolls time interval dllleient bridges dilielent lieq39s mode Medium coupling yieldsa phase K offset that varies linearly with the Intermediate A azimuth angle of the sound source m mode 1 2 I twigggeazm E gii uicoursesrieuros rigidity oi bridge is set quotquot 3 3 red l5 cricket ganglionic nervous syste similar from brainste to spinal cord massive ganglia in he llkE our brain Cricket Ears The cricket s ears are in it s legs front knees The tymganum eardrum is located just below the knee on the rear surface of the foreleg 39 The tympanum connects to an airfilled channel called the tracheal tube which Sound waves thzi ibrate iii tympanum runs through the leg and can reach it lg y39two different routes lnto the bOClY 1 They cm utrike the outer tympanic The tracheal tube connects surface directly from the outside air to a hole in the side of the 2 They can strike the inner tympanic body called the sgiracle surface by traveling into the spiracles outer and Inner circles of the tympanum on erlherside and through the tracheal tube PressureGradient Ears Movement of the tympanum is determined by a pressure gradient difference in air density between the inner and outer surface Movement of the tympanum triggers action potentials in auditory nerve fibers that convey the signal to the prothoracic ganglion stretch mm tympamc and sends APs dendrite tympanum To prothoracic gang on to tracheal system Inside Pressure Outside Pressure wavelength in 1mg if sound travel 1000 ll per sec lrylng to lranSr ml Ideal SlZe of speaker ls the size 039 the wavelength It is SOUI CC successive pulses of compressed air emanating from the sound The wavelength of a sound is the physical distance between Wavelength of Sound distance between successive spacings is longer frequency sounds because the time delay and therefore the spatial Low frequency sounds have longer wavelengths than higher slower oscillations Wavelength of Sound Two Routes to the Tympanum UUHU li uuiev phase olfsel don39t want them is hn at same lime to aHow39 Indirect Route Sound enters the spiracle and travels through the tracheal tube to strike the inner surface of the tympanum longer mute Direct Route Sound travels through the air and strikes the outer surface of the tympanum panum to move OUTER SURFACE crlcket has Circles oi compressed air surrounding its body TYMPANUM INNER SURFACE Indirect route is longer than the direct route The exact difference in the distance between the direct and indirect route is critical for determining the phase relationship between the sound waves hitting the surfaces What would happen if the indirect route was wavelength longer than the direct route How about half a wavelength 35 Cm half a wavelength or halt a wavelenglh plus a wavelenglh elc 00 00 Phase Cancellation Summing in phase vs antiphase waves PERFECTLY lNPHASE WAVES gt CONSTRUCTIVE INTERFERENCE mny rare ed on one swd e 50 when Compressed on one side no reswstance r I 39 A A 1 l 39 J V PERFECTLY ANTIPHASE WAVES DESTRUCTIVE INTERFERENCE 00000000 Summing partially phaseshifted waves cricket not qmte mg enough to m in 35 in so don t get a huge osmHation m close 50 gel preuy good oscillatwon NEARLV lNPHASE WAVES gt CONSTRUCTIVE INTERFERENCE I I I I I J PERFECTLY ANTIPHASE WAVES DESTRUCTIVE INTERFERENCE 39 z W Interaural Intensity Differences Song coming from one side of the female constructively interferes with itself at the ipsilateral tympanum same side as soun source and destructiver interferes with itself at the contralateral tympanum opposite side The phase 39 causes an interaural intensity difference IID an asymmetry in the vibration of the left versus right tympanum female cricket hears the song Wm M g H luusldeclosel male cricket less phase on at quoti opposite side j Wpanum l essentially sound louder 139 on side sound ls comlrgl always rm all four surfaces gm destructive interference at left tympanum E a neulon simulated by audlloly nerve meg veleaY lnlbllly arm on omega Re C I p roca I I n h I b It I O n 0 El llylllg lo tum caell otheroll between Q neurons gels lhe louder sound The cricket s auditory nerve carries action potentials from the ear into the prothoracic ganglion 1 Two sets of omega neurons lullllvnumlwll mum one on the left Slde and one lhese small dllls can excxte i i i ll one mm a n m on the right side are found ln 9 8L M than amevlollmlblemollollzcvone the prothoracic ganglion s engmemng llselHD llre even more MLMM mlm A m gt me Q neurons rCCCIVC exutatory I l l I W input from the ipsilateral ear quotquotquotquot and send inhibitory output to contralateral Q neurons a contrast inhancement small dllls m lnpul result m large dllls ln neural actlvlly quotquot Thus left and right 2 neurons reciprocally inhibit one another This results in a winnertake both lly and evleket 100 small la llx audlmry locallza n plob all iirftang ment Wthll39l lly smallel Solmlonzcuuplclympanllu make are 1 ll l39n am 1 leg 1 e Interaura Left Ear dllls mlmleS ma ol arllmal mm blgger head ng E intensity difference crlckel also a lilclally make Capllallze on phase lol both Exmmal nuclzus Inferior colliculus an Lateral ShelI of cemml nucieus Huhit r r Inferior colhculus 39 Core of central nucleus Inferior colllculus Anterior lmeral 1 lemniscol nucleus Posterior Imam I lemnlscal nucleus T Nucleusangulans l Nucleus mognoceumans Mm Inner ear Ever quotU lzus Convergent input from Inferlor Collxculus T ITD amp ILD tuned neurons Lateral shell of central nucleus quotBe I9 Inferior colliculus my Core of central nucleus Inferior colllculus Anterior lateral i Izmniscul nucleus Posterior lufeml r I lemniscal nucleus T ITD tuned neurons ILD tuned NUCIeUS Nucleus angularxs mugnocellularls me neurons Spatially Tuned Neurons Neurons in ICC more specifically in its lateral shell respond selectively to sounds in a particular region of space The region of space preferred by the neuron is called the cell s receptive field uonenala punos W R Sound alimmh How do they do it Each ICC shell neuron has both an ITD tuning preference and an ILD tuning preference The neuron can only be excited by sounds from sources that match both the preferred ITD and ILD Spacespecific neurons are tuned to respond selectively to preferred interaura time delays 100 2an nf rota spikes lTDiIIs Spacespecific newms are tuned to respand 39 tively to preferred ILD d5 5 0 ion Pm u um spike 1 preferred sound Eocation is derived by combining the preferred s70 xaxis with the preferred iLD yaxis nlevallan may a Azimulh deg Vector and matrices Of neurons 20 map formed lrom elevation and azimuth LD selective cells can be llD Saleeme neurons In conceptualized as a row vector of posterior lateral lemniscus neurons quotear each OWEF Prefer SOUst from similar locations neurons that each prefer f f d 39 d quot different ILDs with adjacent al away We el 59 quot 5 come mm locatlons in space topographlc map due neurons In the row preferrv m is game n ndi hibiii similarILDs r s e t A ITD selective cells can be conceptualized as a column vector of neurons that each prefer 6 different ITDs with adjacent 6 GAO neurons in the column preferring 9 similar ITDs Dorsoventral axis Location selective cells can be conceptualized as a 2D matrix or quotsheetquot of neurons that each prefer different sound locations with adjacent neurons in the sheet preferring similar sound source locations CenterSurround Inhibition inhibit neurons in near exa surround mple oi lateral inhibition process contribute to contrast enhancement magnliy dliieiences Sb iLD selective neurons in 4 l39 osimm posterior lateral lemniscus k i Each ICC cell reciprocally i J ip il H Q Q inhibits its surrounding iiiliq neighbors 31 If ix39 V 4 whichever one get a little more excitation Will quotwin the fightquot and inhlbil those Excitatory center of ICC cell receptive field inhibitory surround of ICC cell receptive field Location selective neurons in ICC shell ILD selective neurons 4 0 8 ICC neurons are still frequency specific so there are many copies of the spatial map in ICC emerem neurons Copled many I r limes to represeni sounds of dill l150 lrequencles V sheets preler cenam frequencies 0 t 0 neurons preler certain m and irequency of sound a 59 some 6 1 00 9 6 100 00 150 150 159 so 150 150 Frequency invariance in ICX Convergent input from spatiallytuned neurons Convergent input from with differing frequency ITD amp ILD tuned neurons preferences we quot frequenc Invarlant 9 Lateral shell of central nucleus quot0quot Hm sensxwe m changes m I9 Inferior co culus 39 quotequency i Core of central nucleus I g Inferior conlculus lLD pam is lrequency invariant 4 Anterior lateral t lemniscal nucleus Posterior lateral 3 1 lemniscal nucleus T lLD tuned Nucleus angularis Auditory neurons ITD tuned neurons l Nucleus mugnocellularis send convergent projections to tax ch uniy needs one of the inputs I not an three to tire irequency anaNal iI representation alter frequency variant representation throw away irequency variance because just need to lei neck muscles to turn and lace the stlmulus only require location not irequency of sound ICX neurons are fre uenc invariant inuudllly 39 Sllmull as ion Convergent input from spatially tuned auditory amp visual neurons Op c Teclum Visual System Convergent input from ITD El ILD tuned neurons fre nsilive q me Lateral shell of central nucleus lmrnq M F Inferior colllculus quot 39 Core of central nucle i Inferior coll ulus Anterior lateral lemmscul nucleus Ponermr lateral 4 lemnlscul nucleus T lLD tuned Nucleus Nucleus angularls magnocellulans neurons Convergent input from quoteq Mariam V spatially tuned neurons with differing frequency 39 preferences ITD tuned neurons Mum Nerve I The spacespecific neurons in the ICX nucleus of inferior colliculus project to the optic tectum Neurons in the optic tectum have spatial receptive fields for both auditory and visual stimuli and these multimodal rece tive fields are normally aligned with one another ICX Auditory map Visual System Visual map Optic Tectum Audiovisual map Constructing invariant representations Optic tectum Modality visualauditory invariant representation of location 0 Frequency but not modality invariant representation of location Amplitude but not frequency invariant representation of location ICC has freq dependoni map lrorn azimuth A iirnml Visual inplll from I I Chlhl and innbran Optic cc leclum l Ill 441 azimuth Tu auditory Ascending ITD inl39nrmalinn in irmLu39m pm ili clmnnclgt Ammur Mullimodnl gtpacc map spam map Prism Studies 0 This young owl is wearing a pair of prism lenses 0 These lenses displace the visual world by 23 degrees but sounds are the same iriiruduce misalignment of visual a d audiiory input 0 llow does wearing prism lenses affect the animal s orienting responses to auditory versus visual stimuli Harm prisms my I um prisms Audiinn auditory response unaffecled buiwsual 1 7 1 look a targei o gt Day 42 11mm removed ailribule simultaneous silmuli in opposite still confused adaptation be lhe same thing look lo 4n doesn39t immediately fix itself will fix iigeil alter long perlod oi lime a ll 441 seeing it through Drle ll l m 710 ill 0 Before wearing prisms the owl s gaze accurately locates both auditory and visual targets U On the first day of wearing prisms orientation to a visual cue is offset by the prisms of course but auditory localization is normal 0 After 42 days of wearing prisms the auditory localization has shifted to match the visual offset THIS ONLY HAPPENS IN YOUNG OWLS When the prisms are removed the shift persists Prism Experience Shifts Receptive Field Alignment A Nl m lal l3 Immediate effect 0 Afters weeks of u prisms prism experience match cells that respond to sound and cells that respond to Visual Sllmull 0 A Before prisms optic tectum neurons have overlapping auditory and visual receptive fields 0 B When prisms are put on the alignment immediately shifts 0 C Over time the auditory receptive field migrates to the new location of the visual receptive fieldlearning iquotSa waysmmdi my ha changes Shift in ITD preference accompanies shift in receptive field l Nnmw39 WWW non zero m c The prisms cause a shift in the azimuth of the receptive field for ICX and optic tectum neurons but not NL or ICC neurons as we shall see Response 2 of maximum llL1ll 1 25 U 25 51 75 XI rmms Since azimuth is encoded by ITD it is expected that the shift quotW mpm Frquot should be accompanied by a 39 39 change the cell s preferred ITD 5 5i u quot Vquot H E 1 r39 o This IS exactly what happens 5 I 39 mphm over time after wearing prisms 400 39 as shown in the graphs at right 3 l 20 Lu 0 R10 2n Visual receptive uld Mimulh dcx Two Types of Glutamate Receptors AMPA amp NMDA W W a F receptor so rt can bind to g utamate and open to aHow runs to quotow through channe PRE POST Very young owl with immature AV map Optic Tectum Retina ICX give avdttory mput Io optic tectum don39t respond to vtsuai and receive input 1mm iCC convergent mic 1mm am neurons that preier am trequenet 09 in a very young owl with an immature AV map the ICX neuron that gets input from the 0quot optic tectum neuron visual field center is weakly excited by ICC neurons that respond to various ITDs Optic tectum neuron 0quot without prisms ICX axon ICX neuron responds wwth W53le 70 J factors ICX dendrite To survive pruning ICC axons must receive growth factors from the postsynaptic ICX cell llashwlth no sound When a Silent Visual stimulus is presented at 0 center of visual field azimuth the optic tectum neuron fires and triggers a small subthreshold EPSP in the postsynaptic ICX dendrite Optic tectum neuron 0quot without prisms ICX axon Presynaptic antiquot 39 potential trifgt s glutamate release trom ten anal o o H H R ICX neuron responds weakly to jiowth factors weak synapse ICC don t respond to visa stimulus so nothing occur ICC here 3X0 sound Withouiilasn When an invisible auditory stimulus is presented at 0 us TD center of azimuth the CC axon at 0 us fires and triggers a small subthreshold EPSP in the postsynaptic ICX spine Optic tectum neuron 0quot without prisms ICX axon noihmg occur in opt teclum synapse ICX neuron responds wwth quot weakly to J factors ICX dendrite Only AMPARs are opened in the postsynaptic spine because NMDARs remain blocked by Mg ions When a visual and auditory stimulus both occur together at the center of azimuth summation of optic tectum and ICC inputs causes a large EPSP to occur in the lCX spine that is postsynaptic to the 0 us lCC axon but not in other 39nes Optic tectum neuron 0quot without prisms ICX axon CX neuron responds wwth weakly to factors weak syn only simultaneous The large summed EPSP depolarizes the spine enough to open NMDARs by removing the Mg block through channel Opening of NMDA receptors allows calcium into the postsynaptic cell which may trigger activation of transcription factor39 in the nucleus of the ICX neuron in developing nervous system hav that Will be pruned il ii is not experiencmg growth iactors Optic tectum neuron 0quot without prisms ICX axon e Connections ICX neuron res onds Transcri t39 V P l3 39 quot iowth weakly to ICX dendrite NMDA calcium also triggers release of growth factors from the ICX spine onto the ICC axon terminal Optic tectum neuron 0quot without prisms ICX axon ICX neuron responds wwth quot weakly to J factors u New synapses initially tend to Growth factors trigger branching and growth of new axons from the ICC cells at 0 us ITD causing the formation of new l probationary synapses ICX dendrite have a higher proportion of NMDA receptors than old synapses Optic tectum neuron 0quot without prisms With time and repeated use the new synapses get off probation ICX axon ICX neuron II t jiowth ICX dendrite J factors responds weakly to weak synapse Eventually the AMPANMDA ratio reverts to norma strengthened inpui trern ICC Young owl before prisms W doiled Imes are weaker synapses boid lines are ICC ICX Optic Visual 223232312 Tectum System 4 kHz get input from neurons that pvefer same iTD wtre mrcuils 6 kHz 855 d up CWCUKS W0 mpuls 0 ex mom Opus Team and I m m i r p s mSCC were once sxmu taneous y activated but no onger ICC ICX Optic Visual Tectum System 39 1 changed coxnmdence re ationships With prisms the optic tectum neuron that used to fire for 0 azimuth will new fire for 20 azimuth Hence for an auditoryvisual stimulus this cell will new fire simultaneously with 50 us ICC cells not 0 us cells Optic tectum neuron 6 20 without prisms ICX axon ICX neuron responds wwth weakly to J factors New axons from ICC to ICX Shifted axons from ICC appear in ICX after 8 weeks of prism experience BEFORE PRISMS AFTER PFHSMS now there are a in of projecnons from CC to iCX Rostral m a new shined iocaiion physically see gmwih at new T lt Learned OHS In ection J lt Normal Slte 500 um no Ionger con1used map rewxred msell 8 weeks after prIsm223522232 quotfi d TD changed to match that ol Opuc Te u ICC ch Optlc Visual Tectum System ur3h 39 KJV oeamh where changes occur are beMeeh 4 kHz CC and CX doesn l occur before ICC Why are old connections weakermwrs Where requency ihvahahee 402 occurs with prisms grow strong excitalory connection and week prior 0 prisms h ml hm d h h t inhibitory connection strengthens to inhibit the excitation ol 2 an 3254322 ex 33 a m normal icc result in net 0 excitation cancels out Normai From Optic tecmm Normal From optic tectum IT lnstructive ITDS Instructive Sig nal 5 Igna an 9quotec lVe39V interneuron in ICX Learned ITDS Figure 6 Changes in neuronal connectivity that accompany the acquisition of a new map of ITD in the ICX a Normal b after prism experience Spheres represent excitatory blue and inhibitory black neurons in the ICX Connections originating from the optic tectum instructive and from the ICC normal lTDs and learned ITDs are represented as semicircles the size of which indicates the strength of the connections excitatory connection inhibitory connection Types of neurotransmitter receptors that support some of the connections are indicated A AMPA N NMDA G GABAA Immediately after prisms removed NHquot can hum with or without prisms ICC ICX Optic Visual Tectum System f w now coniused again in opposite direction accoum ior reversai oi imilai mismatch oi visuai and auditory responses Several days after prisms removed ICC ICX Optic Visual Tectu System Re 02 6 kHz Connectivity changes during prism adaptation In normal owls projections from ICC to ICX are topographically organized to form spatial regions encoding similar ITDs ll umwl 0le Imam u I v Imlllun llulmmk When juvenile owls wear quotWm 39 jl12 l Prisms their developing nervous systems form a new quotquot quotquot om 1 1 l l l 3 1 set of quotshiftedquot topographic 1c ICX 39 quotquot N w w Allmulli connections the old connections are weakened but not eliminated Wu my Sensitive Period for Prism Adaptation A Iuwnilc B Adull a jushncnl mljuslmvnl Mun but TD relative to normal Us in 41 W 30 Time wilh prisms days A Juvenile owls show prism adaptation and then recovery after prism removal recovery not shown 0 B Normal adults show no prism adaptation but those that were adapted as juveniles can readapt as adults to the same displacement that they experienced as juveniles When the owl reaches sexual maturity ICC axons that have not received enough growth factor die away pruning Optic tectum neuron 20 without prisms ICX axon ICX neuron responds weakly to many ITDs ICX dendrite 51 Strong synapse Strong synapse Optic tectum neuron 20 without prisms At this point plasticity of the AV map is no longer possible ICX axon ICX neuron responds weakly to many ITDs ICX dendrite ICX soma Strong synapse an 0 r7 er periorm his adaplaiion Critical periods A 39critical period is a restricted time window during early life when certain processes of brain development MUST occur if they are to occur at all Critical periods or less restrictive sensitive periods have been shown to exist for development of Language Sensory systems visual auditory vestibular Motor skills Social skills Echolocation in Bats Bats Chiroptera Bats are the only flying mammals Bats are similar to primates their five wing bones are homologous with the five fingers of the primate hand There are almost 1000 different species of bats in two suborders megoptera 150 species and microptera N800 species Microptera bats navigate by echolocation The Behavior Echolocation In the 1700 s Lazarro Spallanzani discovered that bats could navigate in complete darkness but owls could not Spallanzani found that bat navigation was severely impaired when their ears were plugged In 1938 Donald Griffin and GW Pearce discovered that bats emit ultrasonic pulses during flight Griffin found that when the bat was prevented from calling by taping its mouth shut its navigation was impaired as if ears were plugged Griffin correctly concluded that bats navigate by echolocation Hearing Frequency Ranges ANIMAL FREQUENCY RANGE 5 Human 2020000 Dog 6745000 Cat 4564000 Cow 2335000 Rat ZOO76000 Bat 20001100quotC Elephant I612000 Porpoise 75lt150000 Goldfish 203000 parakeet ZOO8500 chicken 1251000 Catching Prey in Flight Griffin found that bats could learn to catch mealworms tossed in the air 39 Bats easily learned to discriminate the mealworms from small plastic disks pursuing only the mealworms and not the disks calch prey in mldlllight griffin lesl ii they could what lhey were catching could tell difference belween mealworm and plastic dummy disk can discriminate between objecls with sound Call Rate During Four Stages of Pursuit amp Capture H thmg the echoes 1 the echo trom prey anima 7 39mm n l caHS 102 10 caHs per second 7 5 1 u as close in on may call rate goes way up quot q the bat can39t see until echoes come back to it echoes come back get bnef ash 039 surroundmgs f taster lrame rale means Vewer gaps can quotseequot surroundmgs Manger rate increase dose a prey Io accuralety grab it wequot Echolocation Problems the brain must solve LOCALIZATION PROBLEMS Which direction is the target How far away is the target How is the target moving DISCRIMINATION PROBLEMS How big is the target What is the target Food Echolocation Problems the brain must solve LOCALIZATION PROBLEMS Whh direction is the aarget How far away is the target How is the target moving DISCRIMINATION PROBLEMS How big is the target What is the target Food ITD andlLDiell ou aboullocaiion y Elevation amp Aznmuth Like the barn owl bats use the lLD of the echo to determine the elevation of a target object and ITD to determine the azimuth Unlike the barn owl bats can cock their ears up and down instead of having permanently cocked ears variable ILD Unlike the barn owl bats generate the sound they are listening to barn owls listen for sounds generated by their prey l d l f 4 W I 1 IT Azimuthal angle Elevation Echolocation Problems the brain must solve LOCALIZATION PROBLEMS Which direction is the target How far away is the target How is the target moving DISCRIMINATION PROBLEMS How big is the targe39 r What is the target Food get loud echo either lram small omecl close up or large 0mm far away Angular Size amp Absolute Size The angular size or subtended angle of an object can be measured by the amplitude loudness of the echo louder echoes correspond to larger angular sizes The object39s absolute size actual size can be determined by combining information about the angular size amplitude and distance pulse echo delay of the object absolute size Subtended angle FM versus CF Calls FM CALL broadband lrequency modulaled CF CALL conslam lrequency WWWWW Time Ultrasonic Bat Calls Some bats emit very short lt 5 ms frequencymodulated FM pulses referred to as an FM sweeg Other bats emit longer 530 ms constant frequency CF pulses Many bats use a combination of FM and CF calls CF FM bats As we shall see FM and CF calls serve different purposes IA pmirus A 100 I g A so l K H Illln 5 E 0 Hm 39 39 7 40 mm 5 20 K l l Him 0 l l l I l l I I l l I I B Rhilmlupllm V 100 E l l l quot39l l39 l39l 40 FM Cumpnncnl LE 2 Gizmmpamm m 05 H 03 02 01 0 lime to prey captun39 5 Capture Echolocation Problems the brain must solve LOCALIZATION PROBLEMS Which direction is the target how far avr ay is the target How is the target moving DISCRIMINATION PROBLEMS How big is the target What is the target Food Distance Discrimination Sound travels at a constant velocity so distant or proximal objects produce a long or short delay respectively between the emitted pulse and returning echo James Simmons trained bats to retrieve food by flying to the most distant of two platforms with triangular targe s In this way he used instrumental conditionin as a tool for investigating sensory discrimination pul bats in chamber that absorb echoes hat on one of charq on perch and two plallorms in iron ol rl amnd ruflcctivu target Simmons would shm large to make on closer bet would could echo from both he one that was closer would have an echo as learn platform that is l her away have lead Choice platforms l on h The PulseEcho Delay measures Distance When the triangular targets were replaced with equidistant speakers that played the bat s call back at different time delays in an anechoic chamber trained bats chose the speaker with the longer time delay Bats discriminated pulse echo delays differing by as little as 60 us which corresponds to differences in distance of about 1015 mm HOW DOES THE BAT S BRAIN MEASURE PULSEECHO DELAYS men get rld ol relleciive surfac mic get its cal speakers play lt back l lunhml m cl quoti n Mct n only thing that changes P m bat sllll lly lo speaker with longer pulse echo delay pulse echo delay is now bats locate abject each row is pulse echo trial 86m P72d8 n42dB Pawn usual L p82d3 e52daf FM calls are better than CF calls quot04 n u39n n nr sumw l Inferior Colliculus Neurons exhibit invariant responses to pulse amp echo Inferior colliculus neurons fire action potentials that are precisely time locked to the onset ofthe pulse the echo or both 3 The timing of these action znemons rspnpotentials remains constant mark lime of and echo are so these responses are amplitude invariant By marking the exact time of each pulse and echo these neurons may allow precise measurement of the pulse echo delay for distance calculations for measuring distance why PulseEcho Tuning Curves measure delay of Fm ol pulse and FM of es 0 W whereneltonsT e am of the bat rfnvgrfforspecmcnul se neocortex contains neurons 0 ea sma e act 0 ll y ab cf y that do not respond to a call 39 ea39w Cmemavewpwmpailone or echo alone They map of me to dislance Io my pace code only respond to a pulse followed by an echo 50 Firing response percent max 0 Each neuron prefers a WW specific pulseecho delay Qmseechode ays corresponding to a specific those closer together m conex tuned distance the cell 5 receptive quotaquoty field Neurons preferring different pulse echo delays are topographically arranged on the cortical surface 2 4 6 14 Echo delay quotMB 1y Harmonics 3R HARMONIC Iquot quot A vibrating object generates h oscillations at multiple harmonic frequencies 2ND HARMONIC The fundamental frequency or 1st harmonic is the slowest oscillation iST HARMONIC The second harmonic is twice W the fundamental frequency The third harmonic is three times the fundamental frequency etc gt Time The CFFM call of the mustached bat 120 H4 Frequency kHz Timems The funuamental frequency H1 of the moustached bat s CF call is about 30 kHz but H2 H3 and H4 Datum am are emitted as well The mustached bat is a CFFM bat The bat s call consists of four frequency harmonics H2 is loudest then H3 H4 and H1 The brain uses different components of the call to extract different kinds of 39 ion Lipsfrggumtgatbounces back in echo Io teH what the of sound bounced off PE delay is measured between FM components A M 120 H4 Frequency kHz Timems The fundamental frequency H1 of the moustached bat s CF call is about 30 kHz but H2 H3 and H4 are emitted as well E ipa all sounds emitted lrom bat o comeback The CF component is not good for measuring PE delay because it lasts a long time would you be able to measure an echo by whistling a long note The FM component is not good for measuring PE delay because it lasts a short time would you be able to measure an echo by clapping your hands Since the FM component covers many frequencies it is also good for something else Echolocation Problems the brain must solve LOCALIZATION PROBLEMS Which direction is the target How far away is the target How is the target moving DISCRIMINATION PROBLEMS How big is the target What is the target Food Same note different instruments When an A440 note 440 Hz tone is played on a piano or violin the note is the sameso why do they sound different Because the loudnesses of the harmonics differ 39e a iveamp quot quot quota m i cause ability to differentiate Diiierenl instruments contain diuerent harmonics 3RD HARM JN C 7 HARA VAquotNIC A quot f 39i 39 quot wvmnvvvthu Wit i WV generates more 2nd harmonic 2ND HARMONIC generates more 3rd harmonic lsT HARMONIC WRMONIC e Time Time bals use havmomc content m dxstinguish belween dill ammals objects Harmonic reflection All harmonics go out but they don t all come back quuenry kHz quuency kHz Tim ms Time ms quuenry kHz Echo from mealworm disk re ect 2nd harmonic better orm re ect 3rd bet The Griffin experiment 3 Echo from plastic disk hat echo comes back at diiferen frequency 3 silo measure m H4 FM echo pulse delay 8 quuency kHz Time ms bat measure delay isi harmonic of pulse and multiple hilIonics oi echo 0 A Frequency kHz The FM FM area of the cortex co respond io one harmonic of pulse followed by on harmonic oi echo ic seleggivit in FMFM Cortex e harmoni l5 always 151 harmonic quiet so cani hear other bais39 lsl harmonic armon htains neurons that do not respond to a call alone or echo alone They only respond to an FMl call followed by an FMZ or FM3 echo Furthermore each neuron prefers a specific pulseecho delay corresponding to a specific distance the cell s receptive field Neurons preferring different pulseecho delays are topographically arranged a little radar screen in the brain Frequency kHz 2 4 a 14 mm de39 y may The pulseecho delay axis encodes distance to the target while the harmonic axis encodes identity of the target Echolocation Problems the brain must solve LOCALIZATION PROBLEMS Which direction is the target How far away is the target How is the target movirg DISCRIMINATION PROBLEMS How big is the target What is the target Food harmonicsoiecnoareheipfumm Velocity Bats hunt on the wing and their prey is usually moving as they pursue it so they need to measure velocity of the target 0 They do this by using the doggler shift the perceived change in frequency of a sound emitted by a moving object Doppler shift and utter Time delay the way me pitch 0 object is percelved to Change Percep wquot 039 PM dep 0 how a 395 compressing or rareiying frequency oi sound nol aclually Chan I 9 ng 39 yusl allected by way objecl is moving relativD p pl 5 h to you 0 e r I 39 quot393 Stationary Moving Away I u 39 ing Toward Recall that our perception of pitch depends upon the frequency of the sound wave If the speed at which sound waves are traveling is increased then successive compression waves will hit our ears more frequently increasing the perceived pitch If the speed of sound waves it decreased it will lower the perceived pitch A sound source that is moving toward us adds a constant velocity to the speed of sound and a sound source moving away from us subtracts a constant velocity uliu aypliylau l i By the numbers il movmg away cause cycles lo be farlher parl causing lrequency to be lower sounds lower xa p m when move closer L sound than if just standing Sllii lU aiu uu it sounds lower Afis the change in frequency Doppler shift Av Avis the velocity difference between source amp receiver Af f0 positive for approaching negative for receding c is the speed velocity of soun ms would be more noticeable atgr39gh requency easier lor bats to measure Doppler ellect f0 395 the frequency 0f the source sound ue h h 39 39 Lau e men llequcllhy H anplerEl fectModel m 1 v DopplerE ectMadel m1 t M w B if a J i a i 8 u w llrm39v l m Doppler Shift Compensation 39 As bats close in on a target they alter the frequency of their call so that the dopplershifted echo maintains a constant frequency Frequency kHz This doppler shift compensation is performed only for approaching objects not receding objects 59 Forward swing Backward swing V Lu Frequency Pier M by by do bats Dop s pendulum swing d0 thls have bat sll in from oi pendulum move toward and awe quot0m bat when object move towards bat bat 25quot 3 muency wers frequency of call lo cancel doppler effect it keep frequency 039 echo constant 50 d w en 0 y cl move away from bat doesn t yZHbsteiiTll39ing compensate allow echo 0 come back ve swings lowe when bal closer on prey that IS when I doppler shl ls upward can measure 0 3 veloclly ol prey wllh doppler shllt ow much do l have to lower my call lrequency to keep echo lrequenoy constanW lhis tells Dal velocity of its ore Time s Just like we have lovea ln eye that is very sensitive acoustic fovea most sensitive to frequencies in middle of 2nd harmonic e Acoustic Fovea 39 echo in W e L W m 56quot ec39ha39B he itge l Wltlll he im sr r o l l Eamp JE V range called the acoustic fovea 39 Bats emit their calls near this frequency and doppler shift compensation keeps echoes within the acoustic fovea for optimal detection here uses CF componenlofcall150und source constant freq Tim 1 0f prner39y auditory n u ms is just like plane uses It to measure doppler shit I L mwest rrL am the acous ovea C Humshoe 400 hat 3 E 39u c Musmchcd n 300 bat L g a E 200 5 391 1 Lmlc brown 3 539 b t I 7 100 a Q 1 O r5 0 an 61 8 4 Frequency km Frequency kHz Doppler shift tuning in CFCF Cortex these are the neurons sensitive to doppler shill The CF CF area of the cortex contains neurons that do not respond to a call alone or echo alone They only respond to an CF call followed by a CF echo Furthermore each neuron prefers a specific Doppler shift compensated call frequency corresponding to a specific relative velocity between the bat an the target the cell s receptive field Neurons preferring different Doppler shifts are to o ra hicall arran ed Doppler smn Iell bat ii its movmg towards or away from prey CF CF area measure it call lrequency can shill usuain downi H C dep on which neurons liring tells you il approaching or going away and how last 5 b 90 Echo CF 392 5 60 39 3 g5 30 u Time ms Echolocation Problems the brain must solve LOCALIZATION PROBLEMS Which direction is the target How far away is the target How is the target moving DISCRIMINATION PROBLEMS How big is the target What is the target Food Doppler Shifted Echoes If a bat s call bounces off of a moving object the frequency of the call will be doppler shifted according to the velocity of the moving object The flutter of insect wings can be perceived as a rapidly alternating doppler shift in the echo signal CF calls are better than FM calls for measuring velocity Why A Frequency modulation lt5 Frequency and ampliiude modulation combined Wing moves toward bat Pulse W W 2 Away Away Away Toward Toward Toward Wing moves away from bat Evasive Maneuvers by Moths Some moths have evolved Clever anti bat strategies CF calls repel them causing them to y in the other direction FM calls interrupt their ight CPG causing them to fall to the ground Wall unm dangev l5 gone Some moths can emit ultrasound to jam the bat s sonar can produce fake echoes Midterm will have graphs multiple choice some ma be 39 three or flu Locust F11 ght CPG problems similar to the homework hllpwwwbbcc0uknalurespeciesDeselLLocusl Ever quotU lzus Convergent input from Inferlor Collxculus T ITD amp ILD tuned neurons Lateral shell of central nucleus quotBe I9 Inferior colliculus my Core of central nucleus Inferior colllculus Anterior lateral i Izmniscul nucleus Posterior lufeml r I lemniscal nucleus T ITD tuned neurons ILD tuned NUCIeUS Nucleus angularxs mugnocellularls me neurons Spatially Tuned Neurons Neurons in ICC more specifically in its lateral shell respond selectively to sounds in a particular region of space The region of space preferred by the neuron is called the cell s receptive field uonenala punos HT R Sound alimmh How do they do it Each ICC shell neuron has both an ITD tuning preference and an ILD tuning preference The neuron can only be excited by sounds from sources that match both the preferred ITD and ILD Spacespecific neurons are tuned to respond selectively m preferred interaural kEme delays Percent nf total spikes quot13005 to the right Spacespecific neu rons tively to preferred 39 t evel rencer 20 from above a e c d w 0 0 Patent of mi spiks We preferred sound location is derived by combining the prefererl iTD xaxis with the preferred iiD yaxis nuvanan neg e Azimuih deg VEctorandrnat cesofneurons lLD selective cells can be llD Saleeme neurons In dIMerenl latitudes conceptualized as a row vector of posterior lateral lemniscus neurons that each prefer different lLDs with adjacent neurons in the row preferring similar ILDs ICCsheH 7 preier actual 39 s prefer an azimth a location c O ITD selective cells 39 39 I can be conceptualized as a column vector of neurons that eac neurons in the column preferri g similar ITDs Dorsoventral axis Locationvselective cells can be conceptualized as a 2D matrix or sheet of neurons that each prefer different sound locations with adjacent neurons in the sheet preferring similar sound source locations CenterSurround Inhibition LECTURE FIVE STOPPED HFRZ lLD selective neurons in posterior lateral lemniscus Each lCC cell reciprocally inhibits its surrounding Excitatory center of ICC cell receptive field I I O lnhlbltory r f 9 whalever cell gets mosl excitation compined inhibil eyeryone around ll surround 0 lCC Locatlon selectlve cell receptive neurons in ICC shell field ILD selective neurons 78 e4 0 4 8 ICC neurons are still frequency specific so there are many copies of the spatial map in ICC 00 9 62 W 100 100 400 1 55 150 159 156 150 150 Frequency invariance in ICX Convergent input from spatially tuned neurons Convergent input from with differing frequency ITD amp ILD tuned neurons preferences H Um Lateral shell of central nucleus quot0 I9 Infer r col culus N Core of central nucleus I Inferior colllculus 1 Anterior lateral 39 lemniscal nucleus Posterior lofeml I lemniscal nucleus l ILD tuned Nucleus angularis Auditory neurons ITD tuned neurons l Nucleus mugnocellularls ICC Convergent input from spatially tuned auditory visual neurons Optic Tectum VISUCII System Convergent input from ITD St ILD tuned neurons Convergent input from spatially tuned neurons with differing frequency V7 if preferences r 91quot Infer lus Core of central nucleus I Inferior colliculus f Anterior lateral lemnlscul nucleus Ponenor lateral 4 lemmscul nucleus T lLD tu ned Nucleus Nucleus angularis magnocellulans neurons l lll yrbil ITD tuned neurons Mum Nerve I The spacespecific neurons in the ICX nucleus of inferior colliculus project to the optic tectum Neurons in the optic tectum have spatial receptive fields for both auditory and visual stimuli and these multimodal rece tive fields are normally aligned with one another Visual System Visual map ICX Auditory map Optic Tectum Audiovisual map Constructing invariant representations Optic tectum Modality visualauditory invariant representation of location 0 Frequency but not modality invariant representation of location 0 Amplitude but not frequency invariant representation of location A mmi Visual inpul mm rulmn and innbrain I 2U 4U azimuth Tu auditory V Ascending ITD infnrmallnn in lrmlurnryspwil39ic clunml Alum Mulhnmdal space may pacu map Prism Studies This young owl is wearing a pair of grism lenses These lenses displace the visual world by 23 degrees How does wearing prism lenses affect the animal s orienting responses to auditory versus visual stimuli norm prisms Day I lR23 prisms Audiiun till 7 VlgtLml Day 42 em 7 Before wearing prisms the owl s gaze accurately locates both auditory and visual targets On the first day of wearing prisms orientation to a visual cue is offset by the prisms of course but auditory localization is normal After 42 days of wearing prisms the auditory localization has shifted to match the visual offset THIS ONLY HAPPENS lN YOUNG OWLS When the prisms are removed the shift persists Prism Experience Shifts Receptive Field Alignment A Nnmual 3 Immediate effect C After 8 weeks of isms prism experience 0 pr 0 A Before prisms optic tectum neurons have overlapping auditory and visual receptive fields 0 B When prisms are put on the alignment immediately shifts 0 C Over time the auditory receptive field migrates to the new location of the visual receptive fieldlearning Shift in ITD preference accompanies shift in receptive field l N m39 WWW 39 The prisms cause a shift in the azimuth of the receptive field for ICX and optic tectum neurons but not NL or ICC neurons as we shall see Response 2 of maximum ll l1ll 175 u 5 5n 751m ITDINS Since azimuth is encoded by ITD it is expected that the shift quot WWW ifquot should be accompanied by a 39 39 change the cell39s preferred ITD i 50 u E u l t quot h g 392 r39 o This IS exactly what happens 395 39 I 39 manp m over time after wearing prisms ioo 39 as shown in the graphs at right 20 L10 0 0 Visual receptive eld uimum dug Sensitive Period for Prism Adaptation A Iuwnilc B Adult adjustment adiuslmunl Mem but TD relative to normal its 2 4 80 Time vilh prisms days A Juvenile owls show prism adaptation and then recovery after prism removal recovery not shown B Normal adults show no prism adaptation but those that were adapted as juveniles can readapt as adults to the same displacement that they experienced as juveniles Critical periods A critical period is a restricted time window during early life when certain processes of brain development MUST occur if they are to occur at all Critical periods or less restrictive sensitive periods have been shown to exist for development of Language Sensory systems visual auditory vestibular Motor skills Social skills Before prisms ICC ICX Optic Visual Tectum System 4 kHz 09 Immediately after prisms ICC ICX Optic Visual Tectum System 0 O N G 4kHz quot e 39 we 8 weeks after prisms ICC ICX Optic Visual Tectum System New axons from ICC to ICX Shifted axons from ICC appear in ICX after 8 weeks of prism experience BEFORE PRISMS AFTER PT ESIVIS Rostral lt Learned Injection sue lt Normal 500 um Instructive Signal Instructive Signal Learned ITDs Figure f hmges39 quot quot 39 quot139 0L 39 139quot anew map of ITD in the ICX a Normal h after prism experience Spheres represent excitatory blue and inhibitory black neurons in the ICX Connections originating from the optic tectum instructive and from the ICC normal lTDs and learned ITDs are represented as semicircles the size of which indicates the strength of the connections excitatory connection inhibitory connection Types of neurotransmitter receptors that support some of the connections are indicated A AMPA N NMDA G GABAA Immediately after prisms removed ICC ICX Optic Visual Tectum System 3900 o 609 6039 Several days after prisms removed ICC ICX Optic Visual Tectum System Connectivity changes during prism adaptation In normal owls projections from ICC to ICX are topographically organized to form spatial regions encoding similar lTDs ll nrnwl 0le Imam I v Imlllur KILILIunk When juvenile owls wear prisms their developing nervous systems form a new in mi WMMHNM set of shifted topographic Mml mpquot mmnm winme pxn may connections the old connections are weakened but not eliminated From perception to memory erce tion ngh p p Icon1c memory 8 2 Shortterm memory 4 I 395 PS Intermedlateterm 45b a quot39 1 C1 5 Longterm memory Low Neural Codes Mapping states of the world onto states of the brain A neural code may be formalized as a function f that maps a domain D of quotworld states onto a range R of quotbrain states States of the world become states of the brain works like a function D values on x axis f 3 D a R R values on y axis NEURAL STATES OF THE WORLD y STATES or THE BRAIN A quottime code for azimuth Because of their phaselocking behavior the interspike interval between a left versus right VCN neurons in mammals or nucleus magnocellularis neurons in birds provides a time code for the azimuth of a sound source azimuth of sour goruErcglialnlgl e fggfnq h can represseln eTCFiQgrgmgg gr ode remember sound reaches right VCN or NM rst if sound comes from the right side interval shift between ring of left or right serves as a functin of here the sound is l coming from 0 Negative Positive LEft azrmuth azrmuth or 900 U 90o RghtVCN AZIMUTH ANGLE orNoM E Sound E Cycle 39 Period 39 25 ms azimuth is called 51 set of points that lie on a circle interspike interval where one spike coming from left side and other is coming from right side 4 mafp39ptlh haviime ith dnto interspike interval A pair of monoaural phase locking neurons one from each brain hemisphere can encode the azimuth of a sound source in their interspike interval D values on x axis f f1 gtR7 1 points on circle NEURAL STATES or 200 THE WORLD a 100 e 1 0 2 100 1 E 200 O O 0 4 6 1 gt 90 45 0 45 90 90 45 0 45 90 AZIMUTH degrees AZIMUTH degrees R values on y axis real number line STATES OF THE BRAIN Converting the time code into a rate code MAMMALS VCN neurons send bilateral excitatory direct and inhibitory indirect via NTB projections to the medial superior olive M50 M50 neurons convert the time code for azimuth into a ring rate code for azimuth Left Ear Right Ear Right NTB same state of world different state of the Experienced Range brain L V III l g I I R refers to real number g Best ITD Best ITD line i 5 refers to points on a quotquot circle Right 200 100 0 100 200 Left 39 Leading ITD microseconds Leading aZ39mUth Converted to ring rate Mapping azimuth onto the mean ring rate of neurons in left M50 The mean ring rate of neurons in the left M50 is an approximately linear function of azimuth so MSO maps azimuth onto the ring rate of a neural population D values on x axis f f1 gt1Rf1 R values on y axis points on circle real number line NEURAL CODE STATES OF 40 STATES OF THE WORLD gt E THE BRAIN 3 3O 3 30 E 20 E 20 E 10 1o 9 O I O 90 45 0 45 90 lt gt AZIMUTH degrees 90 45 0 45 90 AZIMUTH degrees Mapping azimuth onto the mean ring rate of neurons in left and right IVISO Together the left and right MSO map azimuth into a planar quot ring rate space where the axes are the mean ring rates in left and right M50 D values on x axis points on circle STATES OF THE WORLD 0 90 45 0 45 90 AZIMUTH degrees STl gtIR72 L r 00h 00 N O A O Left MSO Firing Rate Hz 0 NEURAL CODE AZIMUTH degrees A CDC 2H elea Buuu osw lu la 00 quotquotquotquotquotquotquot quot 1 2300 I 90 45 0 45 90 R values in ZD ring rate space Cartesian plane FIRING RATE SPACE M A O 00 O O Left MSO Firing Rate Hz N O O O 7 1o 39 20 3o 40 39 nght MSO Firing Rate Hz winstead fconverting azimuth one cnvertel int numbers left an riht space corresponds rin of on i n of not fre chne they nt if a when one number azimuth t nuber even tho have o n bers in ring rate reen line Firing rate code is really one dimensional Most of the points in the planar ring rate space do not correspond to azimuth angles Only a linear subset of the plane encodes actual azimuth angles D values on x axis f f1 gtch2 R values on a line in ZD points on circle ring rate space Cartesian plane NEURAL CODE FIRING RATE SPACE A n n a STATES OF 2E 40 40 3 1 only points on THE WORLD 4 z E 40 this line encode n 30 30 8 4 azimuth angles 27 o T m 30 E 20 20 23 27 quotquotquotquotquotquotquotquot 3 5 quotquotquotquotquotquotquot quot to IE 20 U 10 10 g g 0 quotE O O f E s L 90 45 0 45 90 v quot 3 O 0 10 20 3o 40 39 AZIMUTH degrees 90 45 0 45 90 AZIMUTH degrees nght MSO Firing Rate Hz Jeffress Model Right 200 NM Rightinput timecode Right NL 4 49 f I 41gt I r quot I I II I u II I II E ill I I I r I I II ll 1 l I III H r Output place code I I II I abcde LU Leftinpul E timecode m D Z Left 5 NM quotquot Left Leading BARN OWL NM neurons send bilateral excitatory projections to NL neurons which convert the time code for azimuth into a ring rate code for azimuth In this case NL contains a different population of neurons for each ITD that it encodes the quotplace code for azimuth Let us consider three of these populations that encode the left neuron E center neuron C and right neuron A azimuth positions Experienced Range I Neuron A 200 100 0 100 ITD microseconds Right Leading ots ofquot re nt neurnas each prefer ITD as m ural me delay a neuron re re Neuron most for aherte three p referred ring rates thus will have ree points on ring rate space A three dimensional ring rate space The three neurons or populations A C and E map azimuth angles onto a line in 3D ring rate space What if we consider all ve neurons AE this time take 1D azimuth and map onto 3D ring rate space however still just a one dimensional thing begin with a line and end result i if the brain encodes azimuth line D values on x axis line 3 neurons 3D space 39 ns e ne on how azimuths all fall on that f T1 gtCIRT3 pomts on curcle NEURAL CODE STATES OF THE WORLD 90 45 0 45 90 AZIMUTH degrees values on a line in 3D ring rate space FIRING RATE SPACE t E onlypointson this line encode azimuth angles A higher dimensional world space Recall that the locust s ocelli encode the pitch amp roll but not yaw angles of its ight position These two angles de ne a point on a torus D Flight position pitch amp roll only 39 Roll ocelli of locust encode whether it is pitching or rolling ignoring yaw here g 7 2 gt specify must give tWO numbers 2D world 2 numbers just give a plane assumer numbers on line not a circle if on a circle get a torus donuU This symbol is used to represent a space consisting of two angular coordinates which is a torus different points on this donut shaped map each point refer to different pitch and roll Ocelli map flight positions onto ring rates The three ocelli arranged in a triangle map ight positions into a 3D ring rate space Would this work if the ocelli were in a different geometric arrangement D Flight position R Brain states that can pltch amp roll only g f2 R B represent lght posmons In D Flipped Left Pitch Back f OCELLI CMYES39 8 e eve ight 93 NO bottom ocellus Pltchmnm not lit and right NO YES 9amp0 and left are lit Left ocellus lit Q30 Questions map objects to ring rate space In our game of quottwo questions we can imagine a pair of neurons 11 and 12 that re more when the answer to their question is more likely to be yes D object chosen by Objects HRH R Brain states that can thinker represent objects A 3 l 1 Cupcake NEURAL CODE YES quot154 2 Thundercloud Q1 Can it be washed 3 Toothbrush 4 PiCkup TYUCk Q2 Is it bigger than a I I must guess state of world loaf 0f bread 41 questions you choose to ask de ne your NO quotquotquotquotquotquotquotquotquotquotquotquotquotquotquotquot code similar to placing of ocelli NO YES represent these states in brain From perception to memory erce tion ngh p p Icon1c memory 8 2 Shortterm memory 4 I 395 PS Intermedlateterm 45b a quot39 1 C1 5 Longterm memory Low Delayed saccade task 0 1 Fixation Head xed monkey stares at central point Recording electrodes monitors neurons in dorsolateral prefrontal cortex Diagram adapted from Chang M H et al J Neurosci 201213222042216 Delayed saccade task 0 1 Fixation Head xed monkey stares at central point 0 2 Target presentation A spot appears at one of eight locations surrounding the fixation point after a few seconds xation point disappears if you look where it used to be get a squirt of grape juice in your mouth Recording electrodes monitors neurons in dorsolateral prefrontal cortex Diagram adapted from Chang M H et al J Neurosci201213222042216 Delayed saccade task 0 1 Fixation Head xed monkey stares at central point 0 2 Target presentation A spot appears at one of eight locations surrounding the fixation point 0 3 Delay period Target disappears xation is maintained Recording electrodes monitors neurons in dorsolateral prefrontal cortex Diagram adapted from Chang M H et al J Neurosci201213222042216 Delayed saccade task 1 Fixation Headfixed monkey stares at central point 2 Target presentation A spot appears at one of eight locations surrounding the xation point 3 Delay period Target disappears xation is maintained 4 Saccade Fixation point vanished instructing the monkey to look at the former target to obtain reward Recording electrodes monitors neurons in dorsolateral prefrontal cortex Diagram adapted from Chang M H et al J Neurosci201213222042216 Targetspeci c delay period activity Data from Fuster and GoldmanRakic target target xation on off off I t ll l spikes Recording electrodes monitors neurons in dorsolateral prefrontal cortex Diagram adapted from Chang M H et al J Neurosci201213222042216 raphs f rin ependin n Cha position of ta ret in ret keeps rin off rin respcnds Ring attractor network Visual Input A ring of neurons in which Each neuron can be turned on each neuron is tuned to by an excitatory visual input prefer a different target which is activated by stimuli at angle For simplicity we or near its preferred target may imagine that adjacent angle But do neurons keep neurons in the ring prefer firing if this input turns off after adjacent target angles the target disappears think of bein arra ne circular rin formation magine ajacent refer anles C VitV Ump all neu the la ill re d bump Centersurround connectivity sual Input RECURRENT EXCITATION Neurons may excite themselves to stay active after their input turns off a connection scheme referred to as recurrent excitation which makes individual neurons bistable on or off Input RECIPROCAL INHIBITION Neurons may inhibit their neighbors to turn them off In combination with recurrent excitation this causes the network to have peakshaped attractor states al I uro rin nd inputs nes bistable either be r ff if efcite stay keep rin if ets excite neihbrs th eihbors prevent thin from rin 39 recircal inhibitini nei39h rs but The Peak is a stable Attractor State The peak shaped attractor states are quotlow energy states of the network Left on its own the network will always converge to one of these states bottom graph M shows unstable state I I thatwould not be oooooooooooooooooooo supported bythis system must be peak shaped I II OOOOQOOO Attractor states map target angles to ring rate space The peak shaped attractor state can sit at different locations on the ring s perimeter to encode different target positions D Ange to target g f1 ngV R Firing rates of N delay STATES OF neurons In PFC THE WORLD FIRING RATE SPACE NEURAL CODE A only points on this circle encode target angles LLLL n of are of the single angle angle single angle Io if eak run rin eventually f0 l Headdirection HD cells Each HD cell is tuned to fire persistently Whenever the rat faces in its preferred direction Ranck 1984 Taube et al 1992 Different HD cells have different preferred ring directions thus implementing a population vector code for head direction Firing Rate Hz N E S W N 09 909 1809 2709 3609 Head Direction HD tuning referenced to visual cues HD cells remember environments across repeated Visits by aligning their preferred direction with respect to landmark cues Cue card A Firing Rate Hz Firing Rate Hz W N E S W 0 50 1E80 2870 00 0 90 180 270 360 Head Direction Head Direction HD tuning does not require visual cues HD cells still re in their preferred direction when NO visual cues are available their activity is persistent rather than evoked Cue card Firing Rate Hz I 39 Lights Off I I I i m E a 00 E E W N E S W 6 33900 1E80 2870o 99600 0 90 180 270 360 Head Direction Head Direction Population Vector Code From the tuning curve of a single HD cell we can infer the pattern of activity over a population of HD cells Firing Rate max Head Direction The activity peak shifts through the population as the rat turns its head Firing Rate max Head Direction A Recurrent Attractor Network Center Surround Connectivity OOOOOOOOOOOOOOOOOOO Inhibitory Connections ooood 1 5ooooo Excitatory Connections Head Turning Causes a State Transition in the HD Network Stationary Bump Shifting Bump mut HUJIIIII A Recurrent Attractor Network Center Surround Connectivity OQQOOOOOOQQOOOOOOQQ mew H wwmm Neuron Inh39b39tory Neuron right turn Nonnections left turn ooood 1 coooo Excitatory Connections Egocentric versus allocentric reference frames Egocentric means quotself Allocentric means quotother centered so the origin of centered so the origin of an an egocentric coordinate allocentric coordinate system system is located on some is located outside the body in part of the animal s body the external world allocentric focused on external like a compass 0 deg com pass detect N COG Positiveelectromagnetic north azimutWhich is fixed point migratory birds have a magnetic sense allocentricVV Whereas barn owl s center is center of gaze egocentric azimuth 8 Negative azimuth Ijkl Egocentric Azimuth Allocentric Azimuth headcentered coordinates with earthcentered coordinates with 0 reference at center of gaze 0 reference at geomagnetic north HD video Headdirection HD cells Each HD cell is tuned to fire persistently whenever the rat faces in its preferred direction Ranck 1984 T aube et al 1992 The preferred direction is defined With respect to environment centered coordinates and remains the same at all locations Different HD cells have their own preferred firing directions which HD cell remain stable across repeated Visits to the same environment container in WhiCh 1 2 00 l 3600 arnnnaVs IV current Cue card estimate of vvhereits heading aHo cent caHyin afannhar placewith No E0 5 0 W0 N o S familiar 0 90 180 270 360 Head Direction 1809 features 2709 W E 909 Firing Rate Hz Control by visual landmark cues 39 When Visual landmarks that define the environmental reference frame are rotated HD cells rotate their preferred directions by the same amount familiar landmark cues cue card A matter test by changing them around rotate cue card and keep all the rest the same two cells follow rotation of cue card get fooled and think direction changed sense C9quot 1 2 ofdirection reorient N E S W N N E S W N 09 909 1809 2709 3609 09 909 1809 2709 3609 Head Direction Head Direction Firing Rate Hz HD tuning does not require visual cues HD cells still fire in their preferred direction when NO visual cues are available their activity is persistent rather than evoked Cue card If you were blindfolded in a x familiar enVIronrnent you I Lights Off I would still have a sense of direction thusin the dark 1 these HDcells still 1 N fire 5 E w a E a E Equot E E W N E S W W N E S W 09 90 1809 2709 3609 09 90 1309 2709 3609 9 9 Head Direction Head Direction A working memory for allocentric azimuth The population of HD cells functions as a container for storing a working memory of directional heading When the head is not turning a stationary activity bump stores the current head direction When the head turns the activity bump must shift HD signal represent something in a sense that doesn t exist in the world not sens stimulus abstract relatio rf hip between you a I your environment E because indivi ial neurons hav urve can infer this activitSB bump for all I er as rat turns itsgead activity 39 posits and withdrawalgofrom assu o nment Fir Head Direction Angular path integration The bump must shift at a rate that is exactly proportional to the angular velocity of the rat s head as rat turns its head activity bump shift deposits and withdrawals from assumptions of environment Firing Rate max Head Direction an ularvelocit of bum mu be equal t angulalro velocity of rat head head turning Speed Angular velocity measures the angular velocity is just speed and diI ECtiOIl Of rotation Spee j some hmg 395 tummg g Typically angular velocity is O 5 measured in degrees or radians 9039 i per second w The magnitude absolute value of 5 the angular velocity is simply the 3 frequency in Hz times 360 g degrees The sign of the angular velocity defines Whether the direction of rotation is clockwise or counterclockwise Again Sytestibular system senses angular Turn world Into mind state we are concerned with Yaw change in azimuth angle The re a re six 6 B Yaw Rotation around zaxis for head movement I l 3 translational 3 rotational A o 7 quotj a Translation along R011 394 H i y Rotation 39 b the X y amp Z axes around i Pitch x axis Rotation Rotation around the 33131201 x y amp z axes Semicircular canals Vestibular organs of the inner ear Moving around in plane of yaw cause fluid to move around in semicircular canals moving hair cells in ampulla give sense of rotation The utricle amp saccule detect translational movement amp linear acceleration Utricle senses the horizontal B Yaw Rotation plane x amp y axes around zaxis Saccule sense the vertical plane 2 axis The ampullae of the semicircular canals detect rotational movements amp angular acceleration V Utricle y Saccule Roll i Rotatlon around Pitch xaxis Rotation around yaxis Ampulla Ampullae of the semicircular canals At the base of each semicircular canal is a bulbous enlargement called the ampulla which contains an organ similar to the macula of the otolith A layer of hair cells embedded in support cells extend their stereocilia into a gelatinous glob called the cupula When the head rotates in the plane of the semicircular canal fluid circulates in the canal and exerts pressure on the cupula This bends the hair cells in one direction or the other depending upon the direction of the head rotation Cupula displacement Angular acceleration Cupula Q l l l l l I 39 N l I I l u 39l r l l 39I y l r l l Semicircular l canals Semicircular Hair cells Endolymph Ampulla canal flow Vestibuloocular reflex VOR Rotate eyes at exact velocity in opposite of angular velocity of head The vestibuloocular reflex keeps the eyes fixed on a target while the head moves around Sensory neurons from the vestibular nerve project directly to motoneurons in the cranial nerve motor nuclei 1 Detection of rotation 2 Inhibition of 2 Excitation of extraocuiar 3quot extraocuiar muscles LJr muscles on on one quot the other side side 3 Compensating eye movement If httpuploadwikimediaorgwikipediacommonsthumb558Simpev 39 estibuoocuarrefexPNGSOOpXSimpevestibuoocuarrefexPNG Three ring angular path integrator All three rings are composed from HD cells with adjacent cells in each ring having adjacent preferred directions Height of bump is firing rate of cell right below that spot INHIBITORY RING Can use this idea to see where Rat thinks it is EXCITATORY RING INHIBITORY RING Two rings are composed of inhibitory neurons One ring is composed of excitatory neurons All three rings contain their own activity bumps The activity bumps in all three rings remain aligned with one another as they circulate around the rings together The angular velocity of bump rotation is identical to the angular velocity of the animal s headbut how Connections among the rings The three rings end excitatory and inhibitory projections to one another that form a centersurround connection pattern with adiustable symmetry Excitatory cellls excites selves and tho Nearby that prefer similar directions also will excite the cells that prefer the same 039 INHIBITORY Irectlon as them in other ring These bumps still stay oncells still ac even without sensory input you always know you re facing some direction even if EXCITATORY blindfolded RING store these bumps Inhibitory cells CounterclockwiseRlNG direction HD cells in the top ring inhibit excitatory HD cells in the clockwise direction HD cells in the middle ring excite themselves their nearby neighbors and inhibitory HD cells in the top and bottom rings that share the same preferred direction HD cells in the bottom ring inhibit excitatory HD cells in the counter clockwise direction Symmetric vestibular inputs When the head is not turnino the top and bottom rings receive symmetrical input from tonically active vestibular neurons on the left and right sides which holdsthe activity bumps still in the rings 39Semicircular a Canal LEFT vestibular nucleus amp prepositus hypoglossi excite the top ring and inhibit the bottom ring RIGHT vestibular nucleus amp prepositus hypoglossi inhibit the top ring and excite the bottom ring Clockwise asymmetry When the head turns clockwise the top ring is inhibited and the bottom ring is excited so that inhibition decreases in the clockwise direction and increases in the counterclockwise direction This causes the bumps to circulate clockwise Semicircular Canal Se m ici rc u l a LEFT vestibular nucleus amp prepositus hypoglossi neurons DECREASE their firing rates RIGHT vestibular nucleus amp prepositus hypoglossi INCREASE their firing rates If rat turning vestibular neurons on side towards which head is moving increase firing Vestibular neu ns on side turning arvay fr m decrease firing ounterc 0C WISE asymmetry Lose symmetry bump shift to area of less inhibition When the head turns counterclockwise the top ring is excited and the bottom ring is inhibited so inhibition decreases in the counterclockwise direction and increases in the clockwise direction causing the bumps to circulate counterclockwise 4V 7 riff we Semicircular quot ix Ca n al a Ca nal I I tJt RIGHT vestibular nucleus amp prepositus hypoglossi DECREASE their firing rates LEFT vestibular nucleus amp prepositus hypoglossi neurons INCREASE their firing rates P05 is part of cortex each part of cortex communicates with thalamus Ascending HD pathway A 80 E V 60 is g4 40 E 2E 20 X LL I Vestibular O 39W N E S W System 09 909 1809 2702 3609 The HD signal was first discovered in the postsubiculum PoS by James Ranck in 1984 PoS receives strong inputs from the anterodorsal thalamus AD and HD cells were later found in AD AD gets inputs from the lateral mammillary nuclei LMN and HD cells were discovered there as well LMN gets input from the dorsal tegmental nucleus which contains HD cells and gets strong inputs from the vestibular system 80 60 4o 2039 Lesion 1 HD cell was recorded from AD thalamus for 15 minutes and the preferred firing direction was plotted from Blair et al 1999 2 The rat was then picked up and an electric current was injected bilaterally into LMN to destroy it 3 The same HD cell was recorded immediately after the LMN lesion It ceased to eXhibit any directional firing properties but fired constantly at about 10 Hz Hacking the ring attractor What if we make some modifications to this circuit such as feeding velocity inputs from the utricle instead of from the semicircular canals Semicircular canals sense rotational motion utricle sense linear motion 139 If V Iquot I l INHIBITORY UTRICLE RING EXCITATORY RING INHIBITORY RING Sensing head tilt and linear acceleration Hair cells in the utricle are depolarized by backward head tilts or by forward acceleration Hair cells in the utricle are hyperpolarized by forward head tilts or by backward acceleration Depolarization Hyperpolarization Sustained head tilt no linear acceleration Backward Forwa rd 9 Bright s No head tilt transient linear acceleration When the head is upright It Forward acceleration V Backward mam hair cells are at an a intermediate membrane potential and tonically release a moderate amount of neurotransmitter If linear velocity integrated bump would go around ring faster when moving forward like 0 h I i ow many miles you have on your car lg I I i I dometer in Car te s you Grid cell on a linear track ire at fixed distance intervals as if in a ring f integrate linear velocity get linear position F data from Hafting et al 2008 L Mali IlI IIIIIIIIIII ulwl 39IHI IIIH FIT I H mi El Elli E E LIL L 5i 9H r I j II I 39IIII I I 39I II 39 I quot39I II 3939 I 39i39 393 4i II I l ll39 II quot I IIIIIIIIII I I 39II39II39I I E I II 39 39Iquot 39L III IIIII39 I IquotII I 39I II39I IJII I L I II I I I Iquot II I I l39 1 IIII IIIIILII II I III II I39ll I III 39I II E E1 39II I In llquot I III III III II IIII quot II quot I II E 41 I IIIIIII I III III I ll 39II mi 1 II39I39 39IflII39 JIII I 39III39II Ii r III I 39 I 39I I I I I J I 39 quot 39 I I I I I I I D degrees s 360 270 180 Population code for linear rather than angular position Bump s angular velocity depends upon the rat s linear running speed Place cells A firing rate code for space Place cells appear to store a firing rate code for space in much the same way that head direction cells store a firing rate code for direction But DO they D Finite domain of spatial R Firing rate space locations that an animal f D gt R with n dimensions can occupy for n place cells 5 GOOOQQQOOOOOOQ 0 U39 I o I The Morris Water Maze Rats are placed in a tank of water in which a hidden platform is located Rat must learn to swim to the hidden platform to escape from the water BEFORE LEARNlNG AFTER LEARNING Hidden platform From Morris et al 1986 no 7 H II 39 mo E A ll Ki 39 v I Iquot I ha I IIquot II 3 i I u 39I II I 0 Q I It 4039 1 In 39 Q 3 I h 20 5 39n 39 g 1 39 I I I I I I I l I I I 39 l 9 I t uc vigai HIPPOCAMPAL LESION NORMAL Hippocampal lesions impair the water maze task 0 Over several days of training normal rats learn to find the hidden platform quickly from any location in the pool Rats with hippocampal lesions are impaired at learning to find the hidden platform Spatial learning in the water maze may require a form of quotdeclarative memory Probe Trials in the Water Maze HIPPOCAM PAL NORMAL LESION B 40 40 Closest way to test role of hippocampus Training for declara tive memory in roddents 30p Opposite Right Tim39e s 2039 When the platform is removed m normal rats searches mostly in the quadrant of the maze where the platform used to be located but hippocampal lesioned rats search 10 3 4 equallyin aquadrants they don t 5 3 3 A 3 o 3 know where to look 3 g Y Y A 2D attractor network The population of place cells can be a conceptualized as a sheet of neurons We can imagine a bump of activity that shifts across the sheet in correspondence with the rat s movements through the environment Could this sheet of place cells perform linear or translational path integration in much the same way that the ring attractor performs angular path integration If so then place cells may store a quotcognitive map that allows the rat to keep track of where it is within a familiar environment encode rat position on floor bump move across sheet according to rat l movingalong the floor I Ll fl l f f i t sigrfr iff f fq t 39i 39if39i f h Ef iu1 i iii1 4 E r L E k g LF E L 2 i ur m iiil i a arr 4 in r ii in Attractor states map spatial locations into firing rate space The peak shaped attractor state can sit at different locations on the sheet to encode different locations in space D Finite domain of spatial locations that an f R2 RN animal can occupy NEURAL CODE quot39 39quot H 39 39 39quot 39 f r39a r 209 62629 39 r v Aquot o o o 6 63 v fons e99 6 O 39o v39 6 39 7 0 6 c v v69 o5 quot99quotquotquot99 09 K4 9 9 0 9 so 0 360 o Hollow 39 plot firing rate of each neuron where each firing rate is a dimension R Firing rates of N place cells in the hippocampus FIRING RATE SPACE only points on this surface encode spatial locations Three problems with attractor models of place cells 1 The remapping problem Unlike head direction cells which maintain identical adjacency relations with one another at all times even during sleep place cells scramble their adjacency relationships with one another remap when the environment changes 2 The temporal coding problem Attractor models are good for storing and updating via path integration a firing rate code for space but superimposed upon their firing rate code place cells also store a temporal code phase precession 3 The unbounded domain problem Unlike directional heading azimuth which is strictly bounded to lie between O 360 spatial location in a 2D environment is essentially unbounded you can travel infinitely far in all directions Morph box experiments One approach that has been used to investigate how place cells respond to a changing environment is the morph box experiment Stage 1 The rat is exposed separately to two environments square and circle until they become familiar rat run around in square then circle box then morph square until it becomes a circle Stage 2 The square is gradually morphed into a circle or vice versa by gradually shifting the walls In CDC H J I MORPH BOX SHAPE I Each row at left shows data from a different place J 39 39 cell Each column shows the activity of all place cells in a specific box shape Some place cells are active in circle but not square At a certain point in the morph sequence place cells abruptly shift or remap their firing fields When this happens some cells that had not been active in the y a L u square suddenly become active acquire a place field i in in the circle Some place cells are active in square but not circle Conversely some cells tat had previously been active in the square fall silent in the circle Some place cells are active in both circle amp square Some place cells are active in both the square and the circle but when remapping occurs these cells shift their preferred firing locations respect to the walls AND WITH RESPECT TO ONE ANOTHER that is they scramble their adjacency relationships with one other see how they flip from what they do in the square to what they do in the circle Rate remapping versus global rema pin don t maintain adjacency relat onships ith each other change where they fire with respect to walls and to each other also may cause cell to change firing rate amprate remappin i a r The transl Ion from s ape 1 to shape 2 induces RATE REMAPPING All place cells continue to fire at the same locations but their peak firing rates may change cells scramble locations they prefer to fire global remapping or just remapping The transition from shape 2 to shape 3 induces GLOBAL REMAPPING Place cells change the locations at which they fire not only in relation to the environment but also in relation to one another adjacency relationships not the same in each environment might tell animal not only where it is in the environment room but what environment room is is in Encoding different environments The phenomenon of global remapping allows place cells to encode not only where the rat is in a given environment but also which of many environments the rat is currently navigating in For example cells 2 amp 3 fire at different locations in the square shapes 1 amp 2 but at the same location in the circle shape 3 So we can know which shape the rat is in square vs circle from whether cells 1 amp 2 fire at the same vs different times Global remapping might thus provide a basis for storing memories of distinct spatial environments eg your bedroom versus your office Attractor states map spatial locations cells in sheet scrambles and then put back together but Into fIrIng rate space d39acent Iat39onsh39 s are d39fferent a J J39 me39peal39gshape39d attractor state can srt at different locations on the sheet to encode different locations in space reorganize flnng rate space helps you understand that you are only in one space D Finite domain of spatial locations that an f R2 RN animal can occupy R Firing rates of N place cells in the hippocampus ENV39RON39V39ENTA FIRING RATE SPACE 39 I 3 at 3939T39 i r A r 333 9 w waive d9 O 64 0 g r p A 9 g 9 enode locations In a 390 9 0 w 9 0 v r ef gfgsgofofo 4 r let s us make patterns that make sense Remapping good for memory coding but bad for the 2D attractor network model Recall that the 2D attractor model assumes a center surround connectivity pattern whereby cells with adjacent firing fields excite one another and cells with distant firing fields inhibit one another How can this pattern of connectivity be maintained if the adjacency relationships among place cells are remapping between environments This creates a complication for trying to construct an attractor network model of place cells 1 L r I I ll I IL Adi l I I Ar l I I 1 1 L JIILIJI r i i l fi quot F ritifi tifirh r L W iF l L l39 L a L a A 1 r v 39 39 t L l i I p I L s 1 iiiii fati f 39g Ei9i j Fina Killinr 11g 2 if r 1 4 w fffrifftr i l 39 afifll 1 in HIV ii 1 litlll39f tl39i gt 1 391 ii 7 i r 439 5 F iquot 391 Sparse versus distributed codes How many place cells are active in each spatial environment Distributed code Each CA1 pyramidal cell shows a 40 chance of having a place field in any given environment OOOOOOOOOOOOOOOOOO ells in DG only fire in very few locations Intermediate code Each CA3 Sparse code Each DG pyramidal cell shows a 20 granule cell shows a 1 chance of having a place field chance of having a place field in any given environment in any given environment OOBOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOO sparsity of code how many fire at any given time sparse code versus distributed code DG is sparse code CA3 is less sparse and CA1 is distributed not sparse at all Postmortem labeling of immediate early gene IEG RNA with flourescence insitu immediately kill mouse after it goes to new enviro and view its brain hybrldlzatlon new enviro see more red dots PG H IEGs such as cfos zif268 Arc and Homer la 1 i 39 i 39 i39 quot quoti r i quot Hla become activated within minutes after a silent neuron starts ring action potentials If animals are euthanized immediately after a behavioral episode the RNA or protein products of these IEGs can be labeled in postmortem tissue using FISH to identify neurons that were active during the premortem behavior This image shows very little Arc labeleing red in neuron layers of DG and CA3 blue from a rat that was taken from its home cage immediately before death Data from Chawla et al 2005 Hippocampus 15579586 This image shows Arc labeleing in single neurons place cells of DG and CA3 from a rat that explored a spatial environment immediately before death Data from Chawla et al 2005 Hippocampus 15579586 Contextual Fear Conditioning Learning to be afraid of a spatial environment Moris water maze test rat ability to know where it is in environ and where it needs to go 1is test examines rat s knowledge of WHAT enviro it is in this is a diff question I ggVUEE 6 CSUS a Auditory Fear Conditioning sound predicts shock Context Fear Conditioning enviro predicts shock Dorsal hippocampal Lesions Impair Contextual but not Auditory Fear Conditioning When the hippocampus is lesioned soon after CSUS pairings rats continue to freeze to the auditory CS but not to the context where training occurred By contrast unlesioned rats sham controls freeze to both the CS and context impairment in contextual fear response due to damage of hippocampus no place cells that scramble and remind you of the enviro where shock occurred A r lament Cmta mal F F mg 5 i1 WW Tm Fug Fmeing Emilia11a 39 r39 J quot 77 7171ii 1 D39nlJ 1 El a F r J a a a 5 a E E lEIL lilL1 E 3 4 5 E Hlniutsaaa Anagnostaras Maren and Fanselow 1999J Neurosci 1911061114 Hippocampal lesions cause temporally graded retrograde amnesia for context fear Just as humans with hippocampal damage show temporally graded retrograde amnesia left rats show less impairment of context fear if hippocampal lesions are iven lon after trainin rath than immediat I after trainin if you wait a few d ys before gestroy hippocar pus agility to recognize em rdl not as bad g 100 similar to HM no longer newly acquired memory CONTROL 39 SHAM U AMNESIC 39 I HIP LESION g 80 35 80 g labels here are Incorrect fle g o 0 2 60 LC 60 c H I E 39 If39f39 g 3939 I 2 40 3 40 5 e 3 u D o o o IR d 20 quot l 0 510 6 0 710 8390 0 O i 114 2391 2398 DECADE SURGERY DELAY DAYS Squire et al 1989 J Neurosci 980 Kim amp Fanselow 1992 Science 256675 Amnesic Korsakoff s patients show Hippocampallesioned rats show impaired impaired recent memory and intact recent memory and intact remote memory remote memory for public events for contextual fear conditioning Chlamydomonas Reinhardtii A green algae that swims with two agella In the presence of light it can grow well without nutrients Has an eyespot that detects bluecolored light F i i i i ii 39 r U 7 7 J 39 a F quot 7 D 7 imElililTizr39I iirw39ij 7 1quot jut l quot 17 l Proceeding of the National Academy of Sciences 100139405 2003 Charmelrhoosinez a irectly lightegate cationaselective memrane channel Geerg Hegel Tainjef Ezellesii Welfrem lluhni Surieel Kateri39gre39lli lhlene Adeisllwilii Peter Bertheld llj eris llig if Peter HEQEWHMMWF and Ernst Eamberg Mex Plenrltlnstitut f r Biephysiltj Merie urie Etresee iii eeeee Frankfurt Germany 1llnetir tiuit fiilr Eieclhernie Universit t Reenslbur UniversitEtsetresse 3H SEEM Hegehehurg Germany and Institut fiur Eiephyeikelisrhe Ehernie lehehnWelfeng Eeethe Univereitet Bi EEll ltl Ul l la eeeeee Frankfurt Germany I I39irrirriiurliteteze by Walther Siteetlreniue Ul iih EilTEity ef Eeliferhiej Sen Frencigte September eerie received fer retrietrlr April E l BILJ lighi Na channels similar to those associated with glutamate gzxgrIg4 receptors instead of bind glutamate open when blue lightquot y hits them Naquot 3 The algae s eyespot contains a sodium channel that depolarizes the algae cell when it is opened by a photon of blue light in much the same way that an ionotropic glutamate receptor depolarizes a neuron when it is opened by binding a glutamate molecule Optogenetics can we insert channelrhodopsin into a neuron If we did this would we then be able to excite or inhibit neurons with light instead of glutamate In a word yes YFPtagged channelrhodopsin 0 Created by Karl Deisseroth and colleagues Boyden et al Nat Neurosci 81263 2005 o Packaged in a virus usually a lentivirus or adenoassociated virus that can be injected into the brain where it will infect neurons 0 Infected neurons can ectopicallv express the channelrhodopsin A cellspecific promoter sequence virus only affect neurons can be used to limit expression to specific populations of neurons cellspeci c promoter targets desired population of neurons channelrhodopsin gene YFP gene YFPtagged channelrhodopsin Blue light opens the channel to excite the neuron Green light makes the channel glow so we can see which neurons contain the channel and which don t 1 blue light EIFIEFIE EhRE YFP emiEEinh l397 l if ll E iL l J 4 7 Eiii 7 ii 7 1 39 7 l iL i re 4 it 3 i l39 i f Kite e x at t we 17ligi iiig e tag with yfp to make it glow green when hit with light Na Millieeemd limeseale genetically targeted ptieel Cl ilIl quoti neural activity Edwe MI Heydmn 1 Femg Zlmmgli Emmet Eembergmi Gemg Negellm 3 Keri Deieeemtlhli i GREEN LIGHT CAUSES THE NEURON TO GIVE OFF A FLOURESCENT GLOW SO WE CAN SEE THAT IT CONTAINS THE CHANNELRHODOPSON PROTEIN Figure 1 Channelrhodopsin Blue Light K extracellular intracellular Na Blue Light Figure 2 Action Potentials Liu et al 2012 Nature 484381385 Hippocampus is infused with a viral vector containing ChRZEYFP driven by the TRE promoter sequence This promoter only drives gene expression when it is bound by a transcription factor called the tetracycline transactivator tTA The tTA protein is not normally present in neurons so ChR2 is not normally expressed even if a neuron get infected by the virus b Training Dentate gyrus Linking ChRZ expression to IEG activity The experiment is done with mutant mice in which the tTA protein is driven by a cfos promoter Since cfos is an IEG that gets activated when neurons start firing tTA becomes expressed in neurons that have recently started firing which will drive expression of ChR2 in these same neurons The tTA expression system can be turned off by giving the mice antibiotics doxicycline in their water Selective ChRZ expression in DH place cells that fire in a fearconditioned context Liu et al 2012 Nature 484381385 Green labeling shows neurons place cells infected with ChRZEYFP Rats are taken off Before training rats are given DOX during training blue light in context A DOX in context B so that is in the water so tTA amp tTA amp ChR2 will be ChR2 aren t expressed expressed in cfos positive neurons gt gt Doxycyoline No doxycycline Context A Context 8 Habituation FC l l l l l x l 5 days 2 days 1 day DH place cells Selective optical stimulation of place cells that were active in the conditioned context Liu et al 2012 Nature 484381385 After training rats are given Rats are taken Off blue light in context A DOX Before training rats are given DOX durlng tralnlng is in the water again but now blue light in context A DOX in COHteXt B SO that ChR2 is expressed in the is in the water SO tTA amp tTA amp ChR2 Will be neurons that were active ChR2 aren t expressed expressed 1 C39fOS during training positive neurons gt r gt Doxycycline No doxycycline Doxycycline Context A Context 3 Context A Habituation FC Testing lllllx llllll 5 days 2 days 1 day 5 days DH place cells nu Liu et al 2012 Nature 484381385 OPTOGENETICALLY TRIGGERED 20 Test 20 RECALL OF THE CONTEXTUAL FEAR Habitua on 15 MEMORY The graph at right shows that blue light never causes rats to freeze in context A during the habituation session prior to fear conditioning blue line However after fear conditioning in context B the blue light causes rats to freeze in context A Rats do not freeze in context A when the blue light is off 3 min 3 min 3 min 3 min P O gt Doxycycline No doxycycline Doxycycline DH place cells Context A Context 3 Context A Habituation FC Testing Hillx llHH 5 days 2 days 1 day 5 days Three problems with attractor models of place cells 1 The remapping problem Unlike head direction cells which maintain identical adjacency relations with one another at all times even during sleep place cells scramble their adjacency relationships with one another remap when the environment changes 2 The temporal coding problem Attractor models are good for storing and updating via path integration a firing rate code for space but superimposed upon their firing rate code place cells also store a temporal code phase precession 3 The unbounded domain problem Unlike directional heading azimuth which is strictly bounded to lie between O 360 spatial location in a 2D environment is essentially unbounded you can travel infinitely far in all directions Attractor states map spatial locations into firing rate space The peak shaped attractor state can sit at different locations on the sheet to encode different locations in space D Finite domain of spatial locations that an animal can occupy f R2 gt RN nea ne snowmen Just he re a 6 r lt o 699 5amp3 6 a 59969 1 o 1 3 9 v39 r r a u o o 4 o 9 A v 6 9 o o 9 i 909 pag oiog ozo 060 v 0 v v o 9 t Qfng 3123quot u scramble in new environment ENVIRONMENT B e w quot9quot x w r 00 oo 920302 o R Firing rates of N place cells in the hippocampus on sheet not actual ess of preferred firing spaces in worldspace FIRING RATE SPACE A points on one surface Sparse versus distributed codes How many place cells are active in each dslspatidacl env39 ent r n ibute ode nee tognow a out activity of not a Place cells re in 3 enVironmentS more of the cells to know what environment in guy9111quot ff j 47 f space39time trade off harder to read but it is easier to store quot s 39 l quot 39 07 3 o v 3 39 f r I 0 o o v 39 O quot 39V 3 39n 5 39 I 39 On 39 39 39 I u 39 o 39 5 39 g 9 o 39 o I n 39 Distributed code Each CA1 pyramidal cell shows a 40 chance of having a place field in any given environment OOOOOOOOOOOOOOOOOO se code less important to know about multiple ells firing more just about if one is firing Intermediate code Each CA3 Sparse code Each DG pyramidal cell shows a 20 granule cell shows a 1 chance of having a place field chance of having a place field in any given environment in any given environment OOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOO Postmortem labeling of immediate early gene promoter make it only expressed IEG RNA with flourescence insitu when IEG On expressin DG place cells that I when animal off antibiotics hybrldlza uon only in certain environm no longer inhibit channels from bei09iimuleted bright n Dr J 39 I make memory of that enviro IEGs such as cfos zif268 Arc and Homer la Hla become activated within minutes after a silent neuron starts ring action potentials If animals are euthanized immediately after a behavioral episode the RNA or protein products of these IEGs can be labeled in postmortem tissue using FISH to identify neurons that were active during the premortem behavior This image shows very little Arc labeleing red in neuron layers of DG and CA3 blue from a rat that was taken from its home cage immediately before death Data from Chawla et al 2005 Hippocampus 15579586 This image shows Arc labeleing in single neurons place cells of DG and CA3 from a rat that explored a spatial environment immediately before death Data from Chawla et al 2005 Hippocampus 15579586 Millieeemd limeseale genetically targeted ptieel Cl ilIl quoti neural activity Edwe MI Heydmn 1 Femg Zlmmgli Emmet Eembergmi Gemg Negellm 3 Keri Deieeemtlhli i GREEN LIGHT CAUSES THE NEURON TO GIVE OFF A FLOURESCENT GLOW SO WE CAN SEE THAT IT CONTAINS THE CHANNELRHODOPSON PROTEIN Figure 1 Channelrhodopsin Blue Light K extracellular intracellular Na Blue Light Figure 2 Action Potentials artificially make mice brain think it s in a different environment Linking ChRZ expression to IEG activity virus infect DG cells Liu et al 2012 Nature 484381385 Text Hippocampus is infused with a Viral vector containing ChRZEYFP driven by the TRE promoter sequence This promoter only drives gene expression when it is bound by a transcription factor called the tetracycline transactivator tTA The tTA protein is not normally present in neurons so ChR2 is not normally expressed even if a neuron get infected by the Virus b Training Dentate gyrus The experiment is done with mutant mice in which the tTA protein is driven by a cfos promoter Since cfos is an IEG that gets activated when neurons start ring tTA becomes expressed in neurons that have recently started ring which will drive expression of ChR2 in these same neurons The tTA expression system can be turned off by giving the mice antibiotics doxicycline in their water Selective ChRZ expression in DH place cells that fire in a fearconditioned context Liu et al 2012 Nature 484381385 Green labeling shows neurons place cells infected with ChRZEYFP Rats are taken off Before training rats are given DOX during training blue light in context A DOX in context B so that is in the water so tTA amp tTA amp ChR2 will be ChR2 aren t expressed expressed in cfos positive neurons gt gt Doxycyoline No doxycyoline DOX is antibiotic Context A Context 8 Habituation FC i i i l l x H l a before off DOX 5 days 2 days 1 day quot0 Ilght should not cells firing in this fear enviro on Its own Cause express fear response DH place cells Selective optical stimulation of place cells that were active in the conditioned context Liu et al 2012 Nature 484381385 After training rats are given Rats are taken Off blue light in context A DOX Before training rats are given DOX durlng tralnlng is in the water again but now blue light in context A DOX in COHteXt B SO that ChR2 is expressed in the is in the water SO tTA amp tTA amp ChR2 Will be neurons that were active ChR2 aren t expressed expressed 1 C39fOS during training positive neurons gt u gt Doxycycline No doxycycline Doxycycline experimental context same as control 0313 tGXtA COnteXt B contalllligff antibiotics and Habituatlon fear F C Testing has been fear i l i l l conditioned Textl l l iCOIlitioned X 5 days 2 days 1 day 5 days DH place cells Liu et al 2012 Nature 484381385 OPTOGENETICALLY TRIGGERED 20 T t 20 RECALL OF THE CONTEXTUAL FEAR 3 Hisbitua on 15 MEMORY The graph at right shows that blue S 5 Exp 10 light never causes rats to freeze in context A n 12 during the habituation session prior to fear a 10 conditioning blue line However after fear 3 conditioning in context B the blue light causes 5 rats to freeze in context A Rats do not freeze in context A when the blue light is off light on for three minutes off for three minutes repeat 3mir391 3mg 3min 3min freeze with blue light since it remembers fear environment where it was s ocke b O gt rlnakeitremembtDox line No dox c Cline D x lin where it was during yCyC y y 0 ycyc e fear achiSitiOnContext A Context B Come A pmduce SameHabituation F C Testing behavrors as it actually int e ottr i l l l l l i l l envho X H artIfICIally activates days 2 days 1 day 5 days place cells DH place cells Three problems with attractor models of place cells 1 The remapping problem Unlike head direction cells which maintain identical adjacency relations with one another at all times even during sleep place cells scramble their adjacency relationships with one another remap when the environment changes 2 The temporal coding problem Attractor models are good for storing and updating via path integration a firing rate code for space but superimposed upon their firing rate code place cells also store a temporal code phase precession 3 The unbounded domain problem Unlike directional heading azimuth which is strictly bounded to lie between O 360 spatial location in a 2D environment is essentially unbounded you can travel infinitely far in all directions Theta rhythm and Sharp Waves Theta rhythm is a 68 Hz Sharp wave ripples SWRs oscillation that occurs during are synchronous bursts of voluntary movement such as activity that occur mainly When the rat is navigating during quiet wakefulness through its environment When theta is absent i ii quot llii i it Iquot39gt3939lquotlUHquot2331i quot 39lquot iquot quoti M M t 1 W W iwvvquot quot quot39quotquotquotlquotulirli l it39ll i iiquot n 39 i39V i i iiiliiquot39r film mage ehl movement 1 1 Hz to 10 kHz ill 39139 i 2 V 5quot V ai39 u i W331 o J v u J A l quot Ah 0 I1 2quot quotquot2 v gt go 39av 39 flu fvl OL A xJi 39 500 H to 10 kHz 3922 With lump 2 o l v I l 39 H n quot39 x quot39 quot 2 lawquot il39 39il 3 J r h quot v39 a t l39 a o gfu H Il i amp f placed In box 11 inch leTlIl 100 quot3400 Hz 4 U tilllw l quotiquotquoti39i inun 3quotI39H3939l4 quotliquot39ii H I 3 Will39u illquot W si39Ninthinquot 7 o n3 mminitiitil w lw P39Cked Up placed in water 39 Sillml climb om itob39OHz 100 ms I EEG signal recorded at a specific location is called the local field potential or LFP rhythm show firing of hippocampal place cells Phase Precession in Hippocampal Place Cells As the rat passes through the place field the place cell s spikes occur at progressively earlier phases of the EEG theta oscillation Z I Firing phase differs at A versus B even though firing rate is the same record place cell fir 0 very specific thing that v ays happens 3400 23930 160 1quot pl ge cell bursts a theta frequency as rat runs thr gh field of place cell it bursts r mically at theta frequency uto t ertain ace39 hence lacec place cell bursts p at theta frequency 5 l and the LFP phase 4 l of the spike bursts dependsupon and thus encodes Place Field I where the rat is in l the field 180 270 A B Firing rate alone does not distinguish between points A and B because the firing rate is the same at both locations 00 360 bursts are coming at earlier time of spikes clumped in little bursts bursts that happen in phase eaCh me phase PreCGSSIOH middle of place field are greater Graphing phase precession The phase precession phenomenon can be seen in a scatterplot graph where each point corresponds to an action potential with position on the xaxis and LFP phase on the yaxis i I a Place field 340 210 160 100 30 E 1800 I I I I I m U E 2 LL 270 00 360 Place Field 0 50 100 150 200 M Position Cm Place cell spikes burst at theta frequency LFP theta Phase Compressed replay within a theta cycle As a consequence of phase precession place cells fire in an orderly sequence on each theta cycle On each cycle the first cells to fire are those with fields centered behind the rat then cells centered at the rat s current location then cells centered in front of the rat see example cells that fire behind rat in front of rat and where rat is now early stages of theta cells we just left behind 39 340 210 160 340 100 210 etc 100 210 30 160 100 30 180 270 Cell1 39 i Cell2 Phase codes position in fieldcentered coordinates When the rat reverses direction place fields are traversed in the opposite order In this case the spike phases also reverse their order Consequently each place cell s spike phase encodes the distance to that cell s field center along the current direction of travel see example shift in valley show that not just firing rate but also time code that tells where rate is 340 210 160 340 100 210 30 160 340 100 210 30 160 100 30 180 270 00 360 Cell 2 Cell 1 alwavs field entering will fire39 early on t att w tdircthLln rat ist veling w a ce sare lrlng e youw ere elsony time code change Rate or time code Both The phenomenon of phase precession seems to indicate that place cells can simultaneously store two codes for space Rate code firing rate of the neuron depends upon where the rat is located with respect to the boundaries of the allocentric environment Time code spike phase of each place cell depends upon the distance to the cell s field center along the rat s current direction of travel 2D attractor network The attractor network model we have discussed does not on its own offer any clear explanation for the phase precession phenomenon The model can be modified in various ways to account for phase precession but these modifications involve adding new neurons or connections to the model and experiments must be done to investigate whether such features actually exist L r Am m 1 IILIJI a t is r 39 r39 iquot 39 ffff a L L a F It 439quot Ii 113 I39 I 39 i i hr J i39 39 E i 39 iit ifi tii a i m iiiiii r i39 191111 if are L r fi tr l 39 fi fff39ff39i 39 lm In A Three problems with attractor models of place cells 1 The remapping problem Unlike head direction cells which maintain identical adjacency relations with one another at all times even during sleep place cells scramble their adjacency relationships with one another remap when the environment changes 2 The temporal coding problem Attractor models are good for storing and updating via path integration a firing rate code for space but superimposed upon their firing rate code place cells also store a temporal code phase precession 3 The unbounded domain problem Unlike directional heading azimuth which is strictly bounded to lie between O 360 spatial location in a 2D environment is essentially unbounded you can travel infinitely far in all directions Finite versus infinite world state variables Allocentric azimuth that is 39 Allocentric position or distance is directional heading is a finite an infinite world state variable world state variable because there because there is an unlimited set is a fixed and limited set of of locations that one can visit by directions one can face traveling farther and farther in any Consequently a finite number of g39Ven d39rECt39O head direction cells can store all 39 Consequently a infinite number of possible directional headings place cells would be needed to store all possible locations that an animal can visit How does the brain handle this problem Allocentric Azimuth Allocentric Position Adult neurogenesis in dentate gyrus Old neurons for old places and new neurons for new places A Allocentric Position This image was generated in the Lab of FH Gage at the Salk Institute For many years it was believed that mammals were born with all the neurons they would ever have and that no new neurons were generated a process called quotneurogenesisquot in adulthood It is now known that adult neurogenesis does occur in two specific regions of the adult brain the olfactory bulb and the dentate gyrus The microscope image at left shows mature neurons stained in red and newborn neurons cell bodies axons and dendrites stained in green Perhaps new place cells are born in the dentate gyrus to store new memories of novel places that we visit Vaybebut we can do much better than adding new place memories one at a time Cyclical versus linear position or distance This odometer is like a clock with six hands that measures distance on six different spatial scales Adding just one new dial to the odometer multiplies the number of distances we can represent by a factor of ten Could the brain contain systems for measuring distance that work like this Hacking the ring attractor What if we make some modifications to this circuit such as feeding velocity inputs from the utricle instead of from the semicircular canals A EI39anxr I 7 UTRICLE tr RY o m o l EXCITATO RY RING INHIBITORY RING continuous attractor network Samsonovich amp McNaughton 1997 a dv Fuhs amp Touretzky 2006 360 Burak amp Fiete 2009 A Navratilova et al 2012 i 270 39a lVIhatre Gorchetchnikov amp Grossberg 2012 8 625 v 2 180 no cu 5 V 90 8 0 Angular frequency of the bump 0 varies linearly with velocity v at a slope determined by the spatial frequency d1 M of the periodic length interval 2014 Nobel Prize for Physiology amp Medicine Jehm Edve rd MewBr tt Keefe Meser Meser Grid cells in entorhinal cortex CA1 Schaeffer Pyram39dal cells Subiculum Collaterals I Pyramidal Cells Mossy Temporo ammonal Medial P CA31 I Fibers Dentate pathway Entorhinal yrcaerrlll a Granule Cells Cortex Perforant Path spatial pegged 7 gt spatialfrequency d1I I rx I I I I I I I I I I I m lullhi 3939II39I39 IIIIlIIII H E I I I I I i I I quotI I ii I I data from HaftingI Fyhn Bonnevie Moser amp Moser 2008 E I Supplementary Figure 5 FE I I I I 1 4 I 9 E II I I I I I I II 5 quot I I E II I II IIJI I I I I I II I II IIIIIIIII II III II39I ill I I I Iquot I III I II 39 39 I IIIIIIIII I I 39III39 39I II E I III I II II III IIIII39 I III I I39I I I I I 39 39 I II 39I39 39 III II I39IIIIIIIII 39 I39IIII 39Ill 39 II39I I I 39 I EI II39I I 4 I IIII39II II39 IIll I I39Iquot I EH 11 II39 I39 II III I I III I I I III I i I III I I I I I I D I I I39 I I I I I I Position x 70sz Different grid39fells have different vertex spacings 2 e I II I 0 degrees s V distance s MxN neurons 0 degrees s V distance s MxN neurons Ring attractor model of grid cells 1 The remapping problem Like head direction cells and unlike place cells grid cells with the same vertex spacing appear to maintain identical adjacency relations with one another in all environments 2 The temporal coding problem Like place cells grid cells also burst rhythmically at the theta frequency and exhibit phase precession against the local LFPthe attractor model still does not inherently account for this 3 The unbounded domain problem By using several rings each composed from grid cells with a different spacing just like the different wheels of the odometer we can uniquely encode a VAST number of locations enough to cover the surface of the earth many time over Lap number Firing rate Hz Theta phase deg Phase precession in grid cells guruum or 1quot 392 30 0 Like place cells grid cells In entorhinal cortex also show 0 phase precession against the 2 locally recorded EEG theta 20 rhythm 0P1 i 72o 4 3 2 4 Phase precession IS more 80 2 1 a a 13 common In grid cells recorded r 39 quot5 240 g 39 from cortical layer than In is I E3535 quot g s otherlayers 0 6 Position cm Midterm 2 in class Wed Mar 11 Office hours after class on Monday March 9 Review session on Tuesday March 10 in Franz 2258A from 46 pm No office hours will be held after the exam on Wednesday or on Friday March 13 Written Final Exam Thursday March 19 spatial pegged 7 gt spatialfrequency d1I I r x I I I I I I 39 I I I I I I lullhi 39III39I39 I uIIIIIIIIIII H E I I I 1 I i I I 39 I 39 I I data from HaftingI Fyhn Bonnevie Moser amp Moser 2008 E I Supplementary Figure 5 FE I I I I I 4 I HE E II I I I I I II 5 quot I I E II I II IJ39 I I 39I I II 39 I I39IIquotI II 3939 III 39i39 I I I Iquot I III I II 39 39 I II39IIIIII I I 39III39 39I II E I II 39 II LI III IIIII39 I r II I I39I I I I 39 39 j I 39 39II I39I I I 39IIIII I III 39I I I I II I IIII I I II I I I I I I quotI IIII III I II I I E EI IIIII I IIIle II I 39II III I II I39 II III I I39 II EL I I IIII39II II39 III I II39I39III EH 11 II39 II Il39 III I JIII I I I I III I i I III I I I I I I D I I I39 I I I I I I I Position x Hacking the ring attractor What if we make some modifications to this circuit such as feeding velocity inputs from the utricle instead of from the semicircular canals linear speed move bump around the ring bump speed a und ring increase with rat running speed INHIBITORY UTRICLE RING EXCITATORY RING INHIBITORY RING like odometer in your car faster car moves faster odometer moves ampIl larger period smaller frequency Each grid cell bursts at a a Z dv frequency In Hz which IS equal to 360 the number of grid fields traversed A i 270 r per second Burst freq o 360 a 6 2 180 d 3 90 shallower for bigger spacing 8 0 lambda distance per second because makes 360 Angular frequency of the bump 0 varies linearly with velocity v at a slope determined by the spatial frequency d1 M of the periodic length interval Cyclical versus linear position or distance This odometer is like a clock with six hands that measures distance on six different spatial scales Adding just one new dial to the odometer multiplies the number of distances we can represent by a factor of ten Could the brain contain systems for measuring distance that work like this Different grid cells have different spatial periods or quotvertex spacings and thus A different spatial frequencies I firing rate IS the same as expected but pattern is diff fire bursts of spikes at 7Hz II 700 0 degrees s gridcells mid MEC grid cells 3 j dorsal MEC 0 0 V distance s M 72 7L3 Grid cells with different vertex spacings can be thought to reside in different ring attractors which are like different wheels on the odometer f grid cells dorsal MEC 0 degrees s M K2 7amp3 V distance s l midMEC I grid cells 360 27a 180 90 12 2 7zr dzv 0 M x2 x3 r 1 grid cells ventral MEC 1 The bump circulates m in rings with a smaller vertex spacing L which corresponds to a higher spatial frequency d and a steeper slope of the line relating v to a e 3 this is the correct diagram one from last lecture is incorrect Ring attractor model of grid cells 1 The remapping problem Grid cells with the same vertex spacing appear to maintain identical adjacency relations with one another in all environments so there is no remapping problem to worry about 2 The temporal coding problem Like place cells grid cells also burst rhythmically at the theta frequency and exhibit phase precession against the local LFPthe attractor model still does not inherently account for this 3 The unbounded domain problem By using several rings each composed from grid cells with a different spacing just like the different wheels of the odometer we can uniquely encode a VAST number of locations enough to cover the surface of the earth many time over so the unbounded domain problem is less of an issue each time rat passes through either one of grid fields see phase precession occurs over and over again Phase precession in grid cells bursts per second different firing rate because multiple spikes in burst burst at 7Hz firing rate and burst freq are not the same but both measure in Hz d gt T Ral wvn 1W 139 w 30 2O 1O 0 60 4o 201 3quot 0 720quot Lap number Firing rate Hz Theta phase deg 480 240 1 8 quot J I Position cm Like place cells grid cells in entorhinal cortex often show phase precession against the locally recorded EEG theta rhythm Phase precession is more common in grid cells recorded from cortical layer ll than in otherlayers The ring attractor model of grid cells does not provide us with an obvious explanation for phase precession Hacking the ring attractoragain What if we make some modifications to this circuit such as eliminating the bottom inhibitory ring How will the circuit behave now INHIBITORY RING excitatory cells also excite inhibitory cells get walls of inhibition EXCITATORY here only get wall on RING one side allow bump to only move in one direction INHIBITORY RING A ring oscillator CPG With a constantly circulating bump the ring attractor becomes a ring oscillator that could drive rhythmic behaviors like the locust wingbeat cycle ELEVATOR MUSCLES DEPRESSOR MUSCLES Theta cells Rate histogram of a theta cell Compare the firing rate maps of a theta cell place cell and grid cell All burst rhythmically at about 79 Hz but the theta cell lacks spatial tuning Theta cell Place cell Grid cell lll l ill l l i39lli l f il l tl lllilll tile H E j lllt jHL Ring oscillator model of theta CPG A ring oscillator circuit can easily simulate theta cells if the activity bump circulates at the theta frequency of about 8 Hz 0 Each cell in the ring bursts on its own phase of the theta cycle Theta cell spikes lllll II a III llll Illl II lllll Illll Ill Illl llll Theta Frequency Hz 9 N 5 0 9 00 9 03 I 0quot 3 Speed dependence of theta frequency From Jeewajee et al 2008 Hippocampus 1821175 10 20 30 40 Running Speed cms theta freq between 4 and 12 Hz but usually 69 Hz 0 A number of studies have shown that the frequency of theta rhythm in both EEG and singleunit recordings tends to increase slightly with the rat s running speed 0 How can the ring oscillator model account for this dependence of burst frequency on running speed Shift of yintercept The main difference between grid From Jeewajee et al 2008 Hippocampus 1821175 9392 360 Hillim E 270 gas a 180 E86 iii L 90 cells and theta cells is their y intercept 2nd 227 V is slope spatial frequency should say 390 not 2 AW P lIl cgt 10 20 30 40 Running Speed cms running speed zero bump speed zero Speedmodulated theta CPG frequency is some constant plus what it was before if lambda a Q 27rd v UTRICLE W36 1 1 3 o2m A m w tr 2 ollso no 3 8 o If we imagine that the theta ring oscillator receives an excitatory driving input that encodes LINEAR velocity then the theta frequency will increase with running speed from a nonzero baseline When the rat sits still two bumps MOVE in different theta rings but AT THE SAME SPEED or angular frequency so that that they are not moving with respect to EACH OTHER bumps moving at same frequency so not moving with respect to each other exists a reference frame in which bumps are stayin s glltvlv lglEJra tTisgtay ggp U Vl It depends upon what reference frame we measure their position in g I RING 2 J theta cells 875 With respect to the neurons in the rings the bumps are moving But with respect to one another they are not moving So there exists a reference frame in which the bumps are 0 M 7 2 7L3 0 M 7 2 7 3 still when the rat is still V distance s 00 N Um Theta Freq Hz When the rat moves the two bumps AT DIFFERENT SPEEDS or angular frequencies so that that now they are moving with respect to EACH OTHER when rat starts moving frequencies are different YVVWVWVYVWW If running speed modulates the bump frequency with DIFFERENT SLOPES IN EACH RING then the bump frequencies will only be equal when running speed is zero The faster the rat runs the greater the difference between the bumps speeds and thus the faster the move with respect to each other RING 1 theta cells 1 V distance s 0 M x2 x3 Beat interference Sinusoidal tones that differ in frequency or pitch by just one cycle per second 1 Hz are very hard to tell apart from each other 2ms 1996 ms 1Hz is very small difference in frequency 500 Hz 501 Beat interference l x 501500 1 Hz envelop NW N Wm M WWW quot I Oscillatory interference models of grid cells Burgess amp O Keefe 2005 Burgess et al 2005 Giocomo et al 2007 Hasselmo et al 2007 constructively interfere when peaks a iihlme5 5e 08 move in and out of phase beat freq is time for one bump to go 360 degb t period f I SecCycle 2 1 around with respect to other bump I I W WWI IlllI W W I I v f2f1 beat spacing cmcycle Converting a time code into a lace codesound familiar as rat walks across tracks peaks are when t ey are in phase time code for rat s position WVWWVYWW VWWVYVWWWWMYYWW RING 2 1 r theta cells 1 ell The two theta rings store a TIME CODE for the rat s position in very much the same way that the barn owl s left amp right nucleus magnocellularis store a time code for azimuth The grid cells convert the time code into a place code very much like the nucleus laminaris computes a place code for azimuth Do grid cells and place cells derive their locationspecific firing by detecting synchrony among theta cells grid cells come from theta cells grid cell fire when 2 theta oscillator 25 cms 20 cm cells fire in synchrony so happens Ia Grid cell data from Haftlng et al 2008 e i E L 4 5 5 5 g 2W quot 339 5 E E 5 1 I Ildlalil39 Il39lquot 39Ilquotquot3939H I39 Hi m Hun in m vvquot 39 V V l v 1 v 11 a i 5 i i 39 C9 place cell only fire if many theta oscillators fire in synchrony less common so sparse code Place cell data from Foster amp Wilson 2008 l O Firing Rate Hz 5 O l l Position Ascending theta pathways target entorhinal cortex where grid cells are found and hippocampus where place cells are found origin of theta rhythm p 7 b I 13 if drug injected into medial septum 39quot quot Entorhinal Cortex Hippooampus A ten quot Mi 39 f 39 quotquot 39 39 The I 39 a w MOIate histogram of a theta cell Vme f Elm E n i Hill Spatial aloecte39y eulocmrelalion D r 21l39zat1blz Spazid autocorrddticn T39Jjettory r quot Baseline Sub Medial Septum rr 1247 p gm 1 0 E 9 a a I 1 Rate 39neo g39mross 219 sampled W 412541 p 37 m LII z s 12H grooms 071 l t x r K f Inactivation 39r39 02 125 rd39icss 4222 36 Hour Recovery n 374 p 51 1 39r Liaix 910 24 Hour Recovery 039 1311731 ick7 391 2Dl 1 a tilz grdwcss 045 Reprinted from Brandon et al 2011 Theta inputs to grid and place cells can be quotturned of by infusing drugs into the medial septum This temporarily inactivates the projection from medial septum to entorhinal cortex When this is done grid cells in the entorhinal cortex are severely disrupted Brandon et al 2011 Koenig et al 2011 Inactivating medial septum reduces place cell firing rates but spares spatial tuning T E Iidt f inie 3 Ear HIFFEEEHWF UE lELlLE rat 3513 v53 ll39ll j a5lquot ti ratf w TITLE 39 I it t t u I a ME It l3 Before inactivation inact reCOVerV Reprinted from Koenig et al 2011 The grid cell model is supported by the data but the place cell model is not 25 cms 20 cm Grid cell data from Hafting et al 2008 a E L 4 z a 2 i E it I H i I H 93 a 5m 3 3 E E 1 I Il I39IIIJIIEIIII39L ll I I lllll llll 39llll39 llllquotlllll grid ail Place cell data from Foster amp Wilson 2008 0 A 20 8 V EN 8 2 9quot 5 10 gt 0quot A E 39quotVVVVVV39 39VVVV39V39V LL 0 u place POSItIO cell Place cells in hippocampus of crawling bats Each cell fires at one or two preferred locations Different cells have different preferred locations evenly distributed throughout the environment 270 cm 2 Place cell recording in flying bats Example of bat flight trajectory Bat flies in a room containing an artficial tree at the center He flies around the tree to receive rewards from baited branches Bat wears a headstage homing electrodes and wireless transmitters 3D place cells in bats Top view XY Side view YZ Front view XZ Location specificity is preserved in cross sections through all angles 3D path plots and firing rate maps show that this hippocampal neuron fires in a specific 3D location As in rats different place cells prefer to fire in different locations K 10 Hz J 6H2 I l l III L t 1 1 7 p I t A Bat 1 n 10 place cells Ten place cells recorded from the same bat had different preferred firing N locations Hippocampal theta is transient in bats d LFP theta rhythm d E I b f WANNA appears on y In re 339 1s 39 4 25Hz bouts lasting 1 second M ax e There IS no promInent Min theta peak in the LFP power spectrum during S39eep Behav sleep or behavior 481420 4814 20 Frequency Hz Grid cells in MEC of crawling bats Adjacent cells had similar spacing amp orientation but differing spatial phase Dorsoventral gradient of spacings Some grid cells were directionally modulated others not Firing rates were modulated by running speed 9 0quot C 0 I 1 39 0 U C 39 0 j 395 o o 0 ct Entorhinal theta is transient in bats c Entorhinal theta also occurs in brief bouts jk Grid cell firing is present even when theta is absent suggesting that theta is not required for grid cell firing Full writlam Maul It Full With ui Ellhm EEEEJHDI EEH lmut 4 ulnly gl Illt sessilenu HEJIIEZIIIL r r tan 1161 156 crnlyr Do place and grid cells without theta in bats disprove oscillatory interference models Possible explanations Theta is present in bats but for some reason is not being observed Oscillatory interference occurs at a different frequency in bats not theta frequency The oscillatory interference frequency is not constant in bats but instead changes with time 1 Hz 8 Hz 2 Hz etc Midterm 2 in class Wed Mar 11 Office hours after class on Monday March 9 Review session on Tuesday March 10 in Franz 2258A from 46 pm No office hours will be held after the exam on Wednesday or on Friday March 13 Schaeffer Collaterals Subiculum Pyramidal Cells Distributed place cells CA1 Pyramidal Cells Mossy Temporo ammonal Medial CA3 Fibers Dentate Pathway Entorhinal Pyramidal Granule CGHS 39 Cortex Cells Sparse place cells Intermediate place cells Grid cells Medial Septum VVVV Theta rhythm Perforant Path Do grid cells and place cells derive their locationspecific firing by detecting synchrony among theta cells grid cells detect from synchrony of just a couple of theta cells 25 cms 20 cm I I Grid cell data from Hafting et al 2008 e g E E 3 4E I H i 2 z 2 a 2 E quot 339 E S E S 1 g3 2 quot1i5l39il1 3939 Ni V lvllllw quotl lll quoth V v V grid 339 cell Place cell data from Foster amp Wilson 2008 l O Firing Rate Hz 5 O l l Position many diff locations are places where grid cell is active grid cells lots of locations where fire or don t fire place cells only one location where cell fires eg is it a pencil definitivefinal FEATURE CELLS OBJECT CELLS Do you hold it when you use it 2 PencH Is it bigger thana gt 7 A loaf of bread Do most people use it daily 39 Spatial locations are not the only kind of information that could be encoded via this strategy Places to facesand beyond place electrodes in human brains for epileptic patients and were able to test for different stimuli 4 Quiroga et al Nature 43510367 2005 found that neurons in the human a hippocampus can respond to speci c m eg Jennifer Aniston or buildings eg Sydney Opera house 0 Such neurons often responded not only L L L L to pictures of the stimulus as shown at quot J quot left for a Jennifer Aniston cell but also to verbal cues such as the words Jennifer Aniston or Sydney Opera n HOUSE Could these human hippocampal neurons represent people and places face cells and place cells as combinations of features encoded by neurons similar to grid cells FEATURE CELLS OBJECT CELLS Is it 5 person Jennifer Aniston Is it a building Is it a female Does it bringjoy to people 39 Schaeffer Collaterals Subiculum Pyramidal Cells r Temporo ammonal Medial Distributed place cells CA1 Pyramidal Cells Mossy Fibers CA3 De ntate Pyramidal Granule Ces Entorhinal Cells Cortex 3 Hi Sparse place cells 3 0 Intermediate Grid ces place cells Lesion and inactivation I Perforant Path experiments can be carried out to test theories about A I how place and grid cells are formed Theta rhythm Spatial rectoy autocmrelation D 391 21V 9 15h Spatid autoc orrdazicn BOSC39IHO Sub Medial Septum rr 1247 p an a o E 8 U a I Rate 39nco T39Jjeclory A x J I g39idross 219 sampled 39n Q25 3 Jl z m7 1l 2 97 um Inactivation 39r39 02 3 25l I J H 39 l39z 152 36 Hour Recovery rd39Icss 4322 W 374 p Ediquot 39r39 1231 914 24 Hour Recovery n 14347 p sin7 n39 23V 3 ill1 M Reprinted from Brandon et al 2011 grown 046 Theta inputs to grid and place cells can be quotturned of by infusing drugs into the medial septum This temporarily inactivates the projection from medial septum to entorhinal cortex after loss of theta grid cells disappear too temporarily grid cells formed out of theta When thIs IS done grid cells in the entorhinal cortex are severely disrupted Brandon et al 2011 Koenig et al 2011 Inactivating medial septum reduces place cell firing rates but spares spatial tuning in a familiar environment place cells also formed by detect theta rhythm but magma 3 they do not disai oear with theta T E HIF F EK MlF UE EM lELlLE 951 Mg n L rat quot L in I39I39JII II I Ei I39D a tins Before inactivation inact reCOVerV Reprinted from Koenig et al 2011 Place cell stability and remapping are spared in both familiar and novel environments 6 h A Baseline Septal Inactivation recovery 24 h recovery F7 Spatial tuning is preserved not only in a familiar F but 2 Fsl gr V3 7 39 also in a novel N environment that the rat is exposed to for the first time during the inactivation and place cell remapping still occurs between the F and N environments When the rat is returned to the previously novel environment after recovery from inactivation place cells retain the same firing fields 39 they showed during inactivation so they are still 0 8 Q 8 A 3 TI M H H v J E mamas 3 I I able to maintain stable place fields across repeated visits to both environments 5 Eg i Q S o o 1 3305 s 0 a EEE gamete 1 tl quot A f D l 3151 3 I 1 EE quot C It 1062 quot a L 39 051 130 2397 C 6 Brandon et al 2014 Neuron Volume 82 Issue 4789 796 spatial code and temporal code don t destroy each other even without temporal code of theta rhythm spatial code for place cells the same but temporal code is still important The grid cell model is supported by the data but the place cell model is not place cells firing rate code is not disrupted by absence of theta rhythm firing rate not formed by theta 25 cms 20 cm rhythm Grid cell data from Hafting et al 2008 e g E L 4 i 2 z 2 E it I H i I H 39 t 93 a 5m 5 5 5 5 1 I qIII39IIIJII III39L LIIul39lquot 39Iquotquot3939H I39 III M y 4 w 21 t a llll rill r v r i l grid 1 cell Place cell data from Foster amp Wilson 2008 A 20 y s 3 2 quot 5 10 o A E LT vvvaV Vvv 39t v39VVVVVVVv 0 A v V v V pIace POSIth cell The data also does not support models that propose place cells are formed from grid cells Schaeffer Collaterals Subiculum Pyramidal Cells Distributed place cells CA1 Pyramidal Cells V Mossy Temporoammonal Medial Fibers Dentate pathway Entorhinal Granule Cells 39 Cortex A O o O 3 0 Sparse place cells Intermediate place cells Grid cells Medial Perforant Path Septum put toxin into hippocampus obliterate CA3 but keep CA1 intaCt remember when took away Theta rh thm medial septum place cells ok to y fire normally but not grid cells CA1 place cells remain intact after destruction of CA3 spatial firing of place cells intact but behavior impairedfiring normal but rat unable to use information gig3 sg fg1172533 gagfjf yj impaired in morris maze my 3 39i 3 39 l 9 quot 39 t 0 I 39 39 r t lt v a c I 39 n from Brun et al 2002 Science 296 2243 Distributed place cells CA1 Pyramidal Cells Schaeffer Subiculum Collaterals I Pyramidal Cells Temporo ammonal pathway I Mossy Fibers Dentate Granule Cells Sparse place cells CA3 Pyramidal Cells Intermediate place cells Grid cells Medial Perforant Path Septum VVVV Theta rhythm CA1 place cells convey only slightly less spatial information after entorhinal lesions oillllllll In In 10 I I I I I Information density bitsspike 05 l a l n l I l l l I IIIIIIIIIIII A 823 22200 from Brun et al 2008 Neuron 57290 Distributed place cells Schaeffer Subiculum Collaterals Pyramidal Cells r CA3 Mossy Temporo ammonal Medial P d I F39bers Dentate Entorhinal Yraml a Granule Cells Cortex Cells O n B i hzo Sparse place cells 3 0 Intermediate Grid cells place cells place cells don t need grid cells but do grid cells need place cells kind of grid cells at least need hippocampus grid cells made of place cells Medial Septum VVVV Theta rhythm Perforant Path Grid cells are disrupted by hippocampal inactivation Grid cells lose their spatial tuning when the hippocampus is inactivatedbut is this from the loss of place or theta cells J USCl mcI 620 min Place cells in hippocampus of crawling bats Each cell fires at one or two preferred locations Different cells have different preferred locations evenly distributed throughout the environment 270 cm 2 Place cell recording in flying Bat flies in a room containing an artficial tree at the center He flies around the tree to receive rewards from baited branches bats Example of bat flight trajectory fing Bat wears a headstage holding electrodes and wireless transmitters As in rats different place cells prefer to fire in different locations K 10 Hz J 6H2 I l l III L t 1 1 7 p I t A Bat 1 n 10 place cells Ten place cells recorded from the same bat had different preferred firing N locations Hippocampal theta is transient in bats d LFP theta rhythm d E I b f WANNA appears on y In re 339 1s 39 4 25Hz bouts lasting 1 second M ax e There IS no prominent Min theta peak in the LFP power spectrum during S39eep Behav sleep or behavior 481420 4814 20 Frequency Hz Grid cells in IVIEC of crawling bats Adjacent cells had similar spacing amp orientation but differing spatial phase Dorsoventral gradient of spacings Some grid cells were directionally modulated others not Firing rates were modulated by running speed Entorhinal theta is transient in bats c Entorhinal theta also occurs in brief bouts jk Grid cell firing is present even when theta is absent suggesting that theta is not required for grid cell firing disproves earlier hypothesis Full writlam mm It Full With ui bbwt EEEEIDI EEH lbout 4 only gl Ill L EEEElIDFII Ell b utf r r tan 1161 156 only
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