Psych119F Wk4 Psychology 119F
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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 800 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 Human Dog Cat COW Rat Bat Elephant Porpoise Goldfish parakeet Chicken FREQUENCY RANGE Hz 2020000 6745000 45 64000 23 35000 ZOO 76000 2000110000 1612000 75 150000 20 3000 200 8500 1252000 Catching Prey in Flight Griffin found that bats could learn to catch mealworms tossed in the air Bats easily learned to discriminate the mealworms from small plastic disks pursuing only the mealworms and not the disks catch prey in midlflight MWI griffin test if they could I what they were catching could tell difference between mealworm and plastic dummy disk can discriminate between objects with sound Call Rate During Four Stages of Pursuit amp Capture generate calls pulse and it bounces off thing then comes back to its ear the echoes Terminal the echo from prey animal 7 calls 102 10 calls per second 8 9 l I I l l as close in on prey call rate goes way up l I l 39 39 V 39 I the bat cant see until echoes come back to It At 39 7 in f as echoes come back get brief flash of surroundings Ix 0 I I39M faster frame rate means fewer gaps can quotseequot surroundings longed 0 rate increase closer to prey to accurately grab it 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 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 ITD and ILD tell you about location Elevation amp Azimuth Like the barn owl bats use the ILD 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 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 target What is the target Food get loud echo either from small object close up or large object 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 object s absolute size actual size can be determined by combining information about the angular size amplitude and distance pulseecho delay of the object l l I I A I Subtcnded f 1 angle plus 1 4 distance Ila14 f 39 1 7 1 7 I I a lute 512 I I Subtended angle structure of bat calls usually combine FM versus CF Calls FM broadband frequency modulated M fllllllllnlllllllllll llll CF constant frequency WWWw T imc ll Ultrasonic Bat Calls Some bats emit very short lt 5 ms frequencymodulated FM pulses referred to as an FM sweep Other bats emit longer 530 ms constant frequency CF pulses Many bats use a combination of FM and CF calls CFFM bats As we shall see FM and CF calls serve different purposes A Eptcsicus gt 100 u 80 5 1 50 Hum 53 5 40 K l quotquotquotquot39 3quot 20 quot39 Illlll f 1 1 1 1 1 1 1 1 L 1 1 1 1 1 1 B Rhinnluplms h 100 3 quot 39 r rm39n39vm J 1313 40 FM component 5 2 f l5 component 1 1 1 1 1 1 1 1 1 1 1 1 1 06 05 04 03 02 01 0 Time to prey capture 5 T Capture 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 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 targets In this way he used instrumental conditioning as a tool for investigating sensory discrimination put bats in chamber that absorb echoes bat on one of changing on perch and two platforms in front of it simmons would shift target to make on closer bat would could echo from both the one that was closer would have an echo fas 7quot learn platform that is f her away have food Sound rcflective target k Choice platforms 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 pulseecho delays differing by as little as 60 us which corresponds to differences in distance of about 1015 mm 39 HOW DOES THE BAT S BRAIN MEASURE PULSEECHO DELAYS then get rid of reflective mic get its call speakers play it back one speaker plays it later pulse echo delay is the only thing that changes bat still fly to speaker with longer pulse echo delay pulse echo delay is how bats locate object Phantom target 39 Delay circuits Inferior Colliculus Neurons exhibit invariant responses to pulse amp echo Inferior colliculus neurons fire action potentials that are precisely timelocked to the onset of the pulse the echo or both C e 6 each row is p e p p p pulse echo I tria 86 ms 69 ms 54 ms 39 ms g i la 395 3 2 The timing of these actIon g i igneuronsrspnpotentials remains constant e l 39 I 1 5 3 to pulse echoregardless of how loud the pulse a g markt39me of and echo are so these responses zndB s i i 5 3 pulse and p a l r g F gecho are amplitude Invariant e52dB i l 39 l H 3 g a i i 3 ii By marking the exact time of 82 f 1 s 39 each pulse and echo these I e52dB f c 3 y neurons may allow precise measurement of the pulseecho FM 03118 31 6 b61161 than CF 03113 delay for distance calculations for measuring distance Why Firing response percent max IE 5E PulseEcho Tuning Curves measure delay of Fm of pulse and FM of echo tuning curves where neuronsThe area Of the bat L sire moreforspecmc pU39Se nEOCOrtEX COntalnS neurOnS e h d I l t hgfaijYTEJfoif y 0 that do not respond to a call really i cortex have topograpgirone or echo alone map of me to distance to my pr pace code Only respOnd t0 3 pUISE e 1 followed by an echo n I I i I vJ E H Each neuron prefers a neurons tuned for diff Spemfic DUIseEChO dEIayI QU39SeeChOde39ayS corresponding to a specific those closer together 39 in cortex tuned distance the cell s receptive Simi39ar39y Neurons preferring different pulseecho delays are topographicallv arranged on the cortical surface Harmonics 3RD HARMONIC A vibrating object generates oscillations at multiple harmonic frequencies 2ND HARMONIC The fundamental frequency or 1St harmonic is the slowest oscillation 1ST HARMONIC The second harmonic is twice mm the fundamental frequency The third harmonic is three times the fundamental gt frequency etc Time Frequency kHz 120 30 The CFFM call of the mustached bat H 2 CFZ FMZ H h 39 1 CF FMI 0 10 20 30 Time ms The fundamental frequency H1 of the moustached bat s CF call is about 30 kHz but H2 H3 and bat uses harmonics in sound The mustached bat is a CFFIVI 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 informtaation bounces back in echo to tell what the sound bounced off of are emitted as well PE delay is measured between FM components broadband width sound due to many different frequencies due to FM 39 Pullse I 39 120 39 H4 FM4 x 39 39 39 39 It 90 39 I CF3 FM3 395 gt U 60 H quotquotquotquot s g 2 CFZ FMZ h F 30 H 39 quot quot x l CFI FM1 39 b Delay 0 1 l 1 I 0 10 20 30 Time ms The fundamental frequency H1 of the moustached bat s CF call is about 30 kHz but H2 H3 and H4 are emitted as well 5395 all sounds emitted from bat come back 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 re39aiiveampoidi harmomcs cause ability to differentiate Different instruments contain different harmonics 3RD HARMONIC 3RD HARMONIC VVV VWV N generates more 2nd harmonic 2ND HARMONIC 2ND HARMONIC geg a rates more 3rd IST HARM ONIC 15T HARMAQNIQ i W WVVV a i W i i quot i i i i i u 4 i i i r i i i i 4 i ii i M a I 7 tr 1 ii i ii quot 7 77 4 eA 4 J Time Time bats use harmonic content to distinguish between diff animals objects Harmonic reflection All harmonics go out but they don t all come back 120 H4 120 A 90 n3 A 90 3 2 3 2 g 60 H g 60 30 disk reflect 2nd harmonic better worm reflect 3rd better The Griffin experiment Echo from mealworm Echo from plastic dlsk see that echo comes Pullse 5 back at different frequency 120 H4 FM best to measure 120 CF4 FM4 echo pulse delay A 90 H n A 90 g 3 CF3 FM3 g E 39 E 39 60 H quotquotquotquot quotFM 60 2 CF 2 E 2 E 30 bat measure delay 1st harmonic of pulse onics of echo and multiple h l armon respond to one harmonic of pulse followed by diff harmonic of echo ic selectivit in FlVIFIVI Cortex pulse harmoni is always 1st harmonic quiet so can39t hear other bats39 1st harmonic The FMFM area of the cortex contains 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 topographicallv arranged a little radar screen in the brain E Frequency 90 60 30 kHz Frequency kHz 90 F Echo FM3 mealworm FESpOHSIVe Pulse quot FM 1 I I I I disk responsive 0 10 20 30 Time ms Echo Pulse FM PM I I The pulseecho delay axis encodes distance to the target 0 I 210 310 while the harmonic axis encodes identity of the target 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 harmonicsofechohelpfunormis 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 They do this by using the doppler shift the perceived change in frequency of a sound emitted by a moving object Doppler shift quot quot I and flutter Tune delay the way the pitch of object is perceived to change perception 0f pitCh 03999 on hOW air iS compressing or rarefying frequency of sound not actually changing just affected by way object is moving relativeD p p I S h to you 0 e r I Stationary Moving Away Moving 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 when move closer while still generating sound speed of object moves next cycle of sound way physically closer to previous cycle of B the numbers if moving away cause cycles to be farther part causing frequency to be lower sounds lower Example when a plane approaches you it sounds high because it is moving towards you but when passes you it sounds lower Afis the change in frequency Doppler shift AU Av is the velocity difference between source amp receiver Af f0 positive for approaching negative for receding c is the speed velocity of sound this would be more noticeable at gh frequency easier for bats to measure Doppler effect f0 395 the frequency Of the Source Sound because their frequency is so high even small velocity make big difference a Elppplpr Effiaipt flililiiii Ei in 1 a Elppplspr Effeet F ppel in l i l r39 mm lm pleas I 39l39 t mpquotle sales a 39j 5 Li 1 l j 5 L quot i te iziIrllnu eiv 32 LilI39lllraulflf g l EVIL Efflu httpuploadwikimediaorgwikipediacommonsthumb990DoppIerfrequenzgif250pxDopplerfrequenzgif Doppler Shift Compensation As bats close in on a target they alter the frequency of their call so that the dopplershifted echo maintains a constant frequency This dopplershift compensation is performed only for approaching objects not receding objects Frequency kHz p 4 Forward swing Backward swing Echo Frequency do bats 62 Doppler shift by 9 pendulum swing d0 thlS have bat sit in front of pendulum move I toward and away from bat 61 J when object move towards bat bat 1 es g equ y owers frequency of call to cancel doppler 2 3 effect to keep frequency of echo constant 3 when object move away from bat doesn39t 0 Sounds emitted 1 3 5 H h b k by abat during 3 02 compensate a ow ec o to come ac five swings lower when bat closer on prey that IS when 59 I l I 1 doppler shift is upward can measure 0 1 2 3 velocity of prey with doppler shift Time 5 how much do i have to lower my call frequency to keep echo frequency constant this tells bat velocity of its prey just like we have fovea in eye that is very sensitive acoustic fovea most sensitive to frequencies in middle of 2nd harmonic mostsen1s39 ti eC ar39bnrfn eeinasarge vagvte Wtw nove our e The Acoustic Fovea keeps 2nd harmonic of echo in region that its hearing is most sensitive thats why it doppler shift compensates to keep echo within t k In a nyaesrf offrfregatf f r yy range called the acoustic fovea Bats emit their calls near this frequency and doppler shift compensation keeps echoes within the acoustic fovea for optimal detection here uses CF component of call sound source constant freq Tuning Of primary auditory HBUI OHS iS narrowest within the acoustic fovea just like plane uses it to measure doppler shift 3 10 dB Quality factor Q 400 300 200 100 Horseshoe bat Mustached bat 39 Little brown O 30 61 83 Frequency kHz C Threshold sound level dB 80 l Il lllquot I quotV l 52 55 58 64 Frequency kHz Doppler shift tuning in CFCF Cortex these are the neurons sensitive to doppler shift The CFCF area of the cortex contains neurons that do not respond to a call alone or echo alone They only respond to an CF ca 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 topographically arranged Doppler shift tell bat if its moving towards or away from prey CF CF area measure if call frequency can shift usually down dep on which neurons firing tells you if approaching or going away and how fast B l l 90 Echo CE 60 PUISB CF 30 0 i l l l J 0 l O 20 30 Tnmc ms Frequency kHz 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 B Frequency and amplitude modulation combined Wing moves v A toward bat Pulse W Away Away Away Toward Toward Toward Wing moves away from bat Evasive Maneuvers by IVIoths 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 wait until danger is gone Some moths can emit ultrasound to jam the bat s sonar can produce fake echoes Midterm will have graphs multiple choice some maybe L 39 h three or four t problems similar to the homework httpWwwbbcCouknaturespeciesDesertLocust Qrthoptera big hind legs hopping Insect Orders Hymenoptera Ants bees amp wasps Lepidoptera Butter ies amp moths 0 Diptera Flies 39 Coleoptera Beetles 39 Neuroptera Lacewings amp antlions Homoptera Cicada hoppers amp aphids Herniptera True bugs Blattaria Cockroaches Mantodea Mantids Orthoptera Grasshoppers amp crickets Phasrnida Walking sticks 39 Odonata Dragon ies amp damsel ies Ephemeroptera May ies Arthropoda Some are not insects use wings to fly rather than sing like crickets can swarm and ravagedevastate e LOCUSt agricultural crops or grasshopper Thousands of different species throughout the world Mostly diurnal active during daylight Feed on a Wide variety of different plants or dead insects Sometimes they reproduce 1n large numbers and swarm won39t flap its wins unless there is air blowing across it centra pattern generator is important neural system study wingbeat pattern in locust to show how basic circuits work generation of rhythm by nervous system can be used for memory or cognition through oscillations similar to the oscillations found in wingbeat patterns The Locust Treadmill To study locust flight the experimenter tethers the animal in a wind tunnel apparatus When air is moved across the animal it beats its wings A strobe light allows high speed photography of the wingbeat pattern Electrophysiological recordings can also be made as the animal flies examine how neurons are firing during flight The Locust s Wings The locust has two pairs of wings forewings and hindwings Wings do NOT beat together Forewings Hindwings Oscillation a circular motion that repeats 39 I I 39 39 39 Wingsasog0upand down r peatedly n oscillation is a repeating cyclical pattern Any oscillation can be conceptualized as a point can imagine top is compressed and traversing the rim of a circle bottomisrare ed The vertical position of the pooirsi ecshva iighetngW thmwn time to trace a sinusoidal wave Frequency and Period Frequency cycles per second measured in units of Hertz HZ Period Duration of each cycle measured in units of time for example seconds Which oscillation below has the highest frequency Which has the longest period 0m J u WA Frequency and period are inversely related F2 P2 P U W V W phase relative position of something phase are differentobjects are offset that is oscillating to something else P h a S e if one is slightly aheadbehind the other The phase of an oscillation corresponds to its momentary position on the circle Phase can be measured in units of circular angle degrees or radians Phase can also be measured in units of time if we know the period of the oscillation Calculating Phase Sample Problems If the frequency of an oscillation is 5 Hz then what time period corresponds to 90 degrees of phase If 180 degrees of phase corresponds to 10 ms then what is the frequency of the oscillation 1 cycle period equals 3600 I I Relative Phase The relative phase between two oscillations is the distance between their momentary positions on the circle This can be expressed either as a phase angle in degrees or a phase time lag in seconds Phase Time Lag B l 120 90 Wing movement deg S 30 Forewing Hindwing I One wingbeat cycle Hindwing Delay between fore and hindwings Longitudinal depressnrs Vertical depressors Elevators F D E T 2 0 39 Longitudinal depressor5 Vertical depressors I Elevators I l I l 0 20 40 60 Time quot157 ms IS T 1ZOseconds is period because its frequency is 20Hz The Wingbeat 20Hz is the frequegtyCle take 50 ms to complete cycle 75014 14 360504 degrees of separation During flight left and right hindwings beat in synchrony same frequency It takes about 50 ms to complete a single beat cycle so what is the wingbeat frequency The forewings lag the hindwings by 7 ms so what is the phase angle between the two wings Flight Muscles Locust wing movements are controlled by two types of muscles elevators and depressors There are several depressor and elevator muscles for each wing F 4233 ll 39 r r quot l 39 J l r Subesophageal ganglion Thoracic ganglia 8 Brain Tritocerebrum Subesophagcal 51 3 Prothoracic Mctathoracic A T3 AI3 Abdominal 4 A4 Abdominal 5 A5 Abdominal 6 A6 Abdominal 7 A7 Last abdominal J 118 11 The Locust Nervous System The locust body is divided into 3 segments head thorax and abdomen A chain of ganglia clusters of neurons runs through the center of the locust s body The frontmost ganglion in the head is called the m and it receives sensory input from the eyes and antennae Two pairs of connectives link the ganglia together Motor Neurons Prothoracic Elevators This diagram shows motor neurons that innervate the ight muscles Each rectangle is a muscle elevator or depressor Mesothoracic Dots show the number of motoneurons that contact each muscle Metathoracic Numbers label the motor nerves that connect the motoneuron and the muscle brain knows position of all your limbs limbs have proprioceptors in them Proprioception Spinal cord 39 39J quot R A I3939 39 I n i if Golgi tendon organ i 5 Muscle spindle in rill r Ir39 w in I i II Proprioceptors are sensory organs that sense the movement and position of limbs by sensing how stretched the muscle is or how bent the joint is 0 In locusts Wings there are three major types of proprioceptors 1 wing hinge receptors 2 the tegula 3 campaniform sensilla Proprioceptors coordinate wing movements wing hinge receptor is like a rubber band that connects wing to y39 stretch it when wings go UpbW ng H Inge RECe causing proprioceptor to fire WHR is a stretch receptor at the hinge where the wing connects to the body The receptor is connected to sensory neurons that fire action potentials on the upstroke of the wing beat cycle A Wing hinge receptors Dorsal O A 39v A 5 i x I s t f quot i k lbrewing Muscle 85 Anterior Lateral hin 39e r tht raclc F I osti39rtor wall receptor Nerve 1022 Activation of a stretch receptor in ight Smaller amplitude elevations 19999quot 4 Depression 50 ms when wing goes down it pushes have to contract depressor muscle to bring tegua wing down pressure of push causes below shows tegula fires when elevator proprioceptor for tegula to fire muscle fires because the wing is down and elevator must push it up again Tegula is a knobby bump near the front of the wing The receptor is connected to sensory neurons that are activated on the downstroke of the wing beat cycle opposite from the WH R B Tcgula Action of tcgula sensory neurons 11 Hugh 5 mm 1 Lgu la l l kprcssor muscle 97 JWWWWW WWIIHAN39 Elevator musSlv HR H quot l Ono wingbcat Vclc 0 ms Campaniform sensila fires Campaniform Sensillavhenwingsareinthe middle when wings are deformed middownstroke Campaniform sensilla are activated by deformation of the wing during the downstroke Sensory neurons begin firing action potentials at the start of the downstroke and fall silent at the start of the upstroke C Campaniform sensilla Responses of sensory neurons le Distribution of receptors on wings Groups of mechanical wing displacement cam panil39orm sensilla Forvwing a u I 39 39 39 39 n 39 v l o s b uo o a v uw I 39 0 I I A I n o Group nl campanilorm sensilla Hind wing Wing Hinge Receptor When the Winge hinge receptor sensory neuron s axon is electrically stimulated it evokes EPSPs in the depressor motoneurons and IPSPs in the elevator motoneurons when stimulate wing hinge receptor proprioceptor we get excitatory potential for depressors and inhibit elevators 3 amp A Elevators ca m n I Iado opposite ofwing hinge receptors Conversely when the campaniform sensilla sensory neuron s axon is Electrically stimulated it evokes IPSPs in the depressor motoneurons and EPSPs in the elevator motoneurons Anticipates need to bring wing Wing Up upwards again as approach WWmm Wing Down C t g psp 400 ms W Depressors Elevators EPSP Facilitate activationdisinhibits Te u elevator but doesn39t inhibit g depressor 39 When the tegula sensory neuron s axon is electrically stimulated it evokes EPSPs in interneuron 566 IN566 When IN566 is electrically stimulated it evokes EPSPs in elevator motoneurons So the tegula excites elevator motoneurons via 1N5 66 rm WW 4 l Wing Down B lt C 39 Conclusion Proprioceptors activated 3 3 W15mv during one phase of the Wingbeat up vs quotemquot down tend to activate motoneurons of the next phase Why might this be l l 201115 4mV CENTRAL PATTERN GENERATOR 3 motoneurons muscles gt m No proprioceptive feedback is required CHAIN REFLEX Reflex Proprioceptive feedback is required What do Proprioceptors do One possibility Maybe the wingbeat is controlled by a chain re ex that requires proprioceptive feedback A central pattern generator CPG would generate oscillatory activation of the motoneurons without need for proprioceptive feedback A chain re ex is a series of re exes in which the movement generated by one re ex triggers proprioceptive feedback which then acts as the eliciting stimulus for another re ex which then generates more proprioceptive feedback to trigger another re ex and so on How can we test the chain re ex hypothesis in the locust Donald Wilson s experiments early 1960 s The proprioceptive feedback was eliminated by cutting the sensory nerves from the wing to the nervous system deafferentation The wingbeat frequency dropped from the normal rate of 20 Hz down to about 10 Hz but the locust still beat its wings rhythmically in the wind tunnel So proprioceptors modulate the wingbeat pattern but they are not essential for generating the pattern Conclusion The wingbeat is not controlled by a chained reflex circuit Maybe a CPG but how can we locate the neurons that form the CPG if you get rid of proprioceptor input still flap wings but frequency reduction occurs this cannot be explained by the chain reflex model explained by circuit that sends cyclical demands central pattern generator the proprioceptors do not cause flight thus we don39t have this chain reflex model CPG neurons must fire in synchrony with the wingbeat pattern correlation 39 Wing muscle motoneurons fire in synchrony with the Wingbeat see figure Thus hey pass the correlation test But are they part of the Wingbeat CPG How can we test this correlation test B Motor neurons I aCthlty Of neuron One wingbcat cycle correlated with Elevators DCPTPSSOI39St behavior Fnrew i n g Hindwing f 100 ms I 10 mV Hindwing l l SOms Forewing RESET EXPERIMENT HOW can We identify a neuron that is part of a CPG Just because a neuron fires in synchrony with the pattern that doesn t mean it participates in generating the pattern It might just be following the CPG RESET EXPERIMENT CPG motoneurons muscles Inactivation of a downstream neuron 1 Record the oscillatory neuron and temporarily inactivate it 2 If CPG oscillation resumes with the same phase after inactivation then not a CPG neuron Inactivation of a CPG neuron 3 If CPG oscillation resumes with a phase shift after activation then could be a CPG neuron when stop messrng wrth neuron It Will come back and oscillate again does it come back in exactly at phase it would into neuron and mess39it up reset test have been in if you hadn39t messed it up or does this mess up the pattern does it start with a new phase if does you can infer you messed with central pattern generator if pass neuron is part of central pattern if doesn39t it was just a slave neuron generator All wing motoneurons in the locust about 80 of them fail the reset test Therefore motoneurons are not part of the CPG circuit Most likely candidates for CPG neurons are interneurons that project to motoneurons IN 30 N 511 M112 Some interneurons fire in synchrony with the wingbeat pattern Keir Pearson amp colleagues conducted many studies in which they recorded interneurons from locusts While they were ying in the Wind tunnel They found that many of these neurons fired in synchrony with the Wingbeat pattern They filled the cells With dye to Characterize their branching patterns and identify which other neurons they made connections with N501 passes the reset test During ight INSOl is strongly depolarized This shifts the phase of the ight rhythm Thus INSOl passes the reset test and appears to be part of the ight CPG Dcp0arizatiun of N50 INSD J J J Dcprcssor W muscle JC 3 r J 7 A N301 M 39NS W i 8 INS IOmV 20 mV N301 12 it man We 1 10 mV 10 mV 10 mV 20 mV P d 25 ms D mm W 10 mV INSOI ZSmV l Paired recordings reveal connections between interneurons Electrodes are inserted into two neurons that are connected to one another and one neuron is briefly stimulated A INSO4 excites N301 B N301 inhibits N511 C N301 excites INSOl after a short delay D INSOl inhibits N301 Feedback Inhibition IN301 excites INSOl which in Toniclnput turn inhibits IN301 Such feedback inhibition can convert tonic input into phasic output If IN301 receives tonic input it might excite INSOl after a delay A One wingbeat cycle WOUld and turn it off which would cut off 39 INSOl s input and turn it off INSOI which would relieve IN301 from inhibition and the whole cycle ISmV would start over N301 During ight IN301 and INSOl exhibit exactly this temporal Depressor muscle 112 13311611 100 ms N301 and N501 are small parts of a much larger and more complex CPG circuit that controls the wingbeat notice that N301 does not actually excite INSOl but disinhibits it lto 0 l 5 K 333 r1 E r I Mm motor k l 4quot 2 3 Sufficiency without necessity Tegula sensory neuron passes the reset test During ight tegula sensory afferents are stimulated This shifts the phase of the ight rhythm Thus the tegula passes the reset test and appears to be part of the ight CPG though not a critical part as we have already seen Flight motor neuron Motor WW rhythm l 10 mv Stimulation 0f ms tcgulae afferents A Yaw Windsensitwc hairs eye Compound 004 H 2 3 Flight control How can the locust maintain level flight in a wmdy world How can it avoid obstacles There are three axes of rotation that must be stabilized in order to maintain level flight pitch roll and 3a The locust has three ty es of exteroreceptors that al ow it to sense the world around it and maintain stable flight Windsensitive hairs Compound eyes Ocelli three simple eyes Extero receptors Compound eyes are capable of detecting deviation in all three rotation axes but they integrate complex information which takes a long time so the response times are slow Windsensitive hairs respond much faster but mainly detect deviations in yaw and pitch not roll Ocelli also respond quickly but only detect deviations in pitch and roll Locust seye ocelli view Roll Correction LEVEL FLIGHT L amp R oeelli equally illuminated SKY left right ROLL LEFT L dark R light ROLL RIGHT L light R dark SKY SKY Locust seye ocelli view Pitch correction LEVEL FLIGHT L amp R light M dark SKY Pitch forward All dark Pitch back All light SKY SKY DeviationDetecting Neurons DDNs B Nl DN M DNC 1 2 3 Heinrich Reichert and Frazier Lowell have studied neurons in the brain which receive input from the ocelli and send descending projections to the flight system in the ganglia These deviationdetecting neurons DDNs come in three major types DNI Receive input from the ipsilateral oceHus DNIVI Receive input from the medial oceHus DNC Receive input from the contralateral ocellus Each type of DDN is specialized for detecting certain types of course deviation during flight Rolling the horizon to simulate flight Rolling the horizon RIGHT simulates What happens when the locust rolls LEFT SKY Rolling the horizon LEFT simulates What happens when the locust rolls RIGHT GROUND SKY m GROUND SKY GROUND SKY GROUND Example DNC neuron on the right side of the locust V Roll horizon right to simulate left turn left oeellus goes from light to dark from light to dark Roll horizon left to simulate right turn right oeellus goes How would this neuron fire in these two cases Example DNC neuron on the right side of the locust When the horizon is tilted right to simulate a left turn the left ocellus switches from light to dark A DNC neuron on the right side of the brain which receives input from the left ocellus fires action potentials in response to this darkening of the left ocellus during the leftward horizon roll The same response can be elicited just by darkening the leftward ocellus without rolling the horizon Where might this neuron send its output 8 Response to visual input Right interncurnn 1 Roll horizon left l 4 ls On r i r l 3 1 Off Alr current 1 400 ms Correcting a leftward roll Roll horizon right to simulate left turn DNC neurons excites speeds up left wingbeat to prevent leftward roll THOUGHT QUESTIONS How would DNI neurons on the right side of the body behave during this same leftward roll What about DNI neurons in the left side What would happen during a rightward roll Under what Circumstances might DNM neurons respond to ight path deviations DNC neuron inhibits slows down right wingbeat to prevent leftward roll The moth to the flame