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Exam 2 Study Guide

by: Emma Notetaker

Exam 2 Study Guide NSCI 3320

Emma Notetaker
GPA 3.975

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Comprehensive study guide covering lecture notes and group projects
Systems Neuroscience
Laura Schrader
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Popular in Systems Neuroscience

Popular in Neuroscience

This 26 page Bundle was uploaded by Emma Notetaker on Wednesday March 9, 2016. The Bundle belongs to NSCI 3320 at Tulane University taught by Laura Schrader in Spring 2016. Since its upload, it has received 88 views. For similar materials see Systems Neuroscience in Neuroscience at Tulane University.


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Date Created: 03/09/16
Wednesday, March 9, 2016 Exam 2 Shared Syntactic Integration Resource Hypothesis • language processing in the brain • major structures • primary auditory cortex Broca’s area: speech production • • opercular and triangular parts of inferior frontal gyrus • Wernicke’s area: speech comprehension • posterior portion of superior temporal gyrus • arcuate fasciculus: fibers connecting Broca’s and Wernicke’s area • music processing many areas • • pitch analysis in right temporal • primary and secondary auditory cortices in temporal relations • motor cortical areas involved in rhythm • connection between right temporal gyrus and frontal cortical areas important for working memory in music appreciation inferior frontal gyrus (Broca’s) involved in analysis of musical syntax • • syntactic vs. semantic processing in language • syntactic: how brain combines words into constituents and sentences • Broca’s area (regions in/around inferior frontal gyrus) • superior temporal gyrus/sulcus • left anterior temporal lobe semantic: how structural and semantic information is used in the understanding of • sentences • Wernicke’s area • inferior prefrontal cortex • syntax in music and language: • hierarchically organized sequences of basic elements language: phenomes, morphemes, words • • music: notes and chords • lower-level units arranged according to rules • language: complex words, phrases, sentences • music: motifs, phrases, movements • dependent on long-term memorized representations language: knowing lexical knowledge and the meaning of specific combinations of • words • music: memorizing familiar tunes as specific sequence • dissociation evidence: • aphasia: speech/language impaired in either auditory comprehension, verbal expression, reading/writing or functional communication patients that were aphasic after removal of left hemisphere or after stroke: • • restricted speech • able to recover word articulation with support of melody • due to the fact that language lateralized to left hemisphere BUT music in both (not necessarily true - new research) 1 Wednesday, March 9, 2016 • overlap evidence: • BA 44 (part of Wernicke’s) activated in response to unexpected chords in music in music, activation is bilateral but only left in language • • posterior and anterior superior temporal cortex active in people who encounter unexpected chord/instrument • similar ERP patters to syntactic violations of language and harmonic deviations in music • theories of reconciliation: • how can neurological overlap exist alongside behavioral dissociation - relationship modular or shared? • importance of comparative research • functional and neural architecture in both domains • role of different brain areas in hierarchical processing of complex sound sequences • broad principles of cognitive organization for complex info systems • shared syntactic resource integration hypothesis (SSIRH): language and music care a common set of processes that operate on different structural • representations • processing resources in frontal areas • representation regions in posterior brain areas • based on domain-specific cognitive theories of syntactic processing • comparative analysis best when driven by hypothesis, which requires consideration of empirically supported cognitive theory in both domains • dependency locality theory (DLT): • accounts for differences in complexity of grammatical sentences and for preferences in interpretation of syntactically ambiguous sentences • linguistic syntax requires: • structural storage: keeping track of predicted syntactic categories (expect verb after noun) • structural integration: connecting words to prior words • predicts that processing cost increases with distance between incoming elements and site of integration • processing cost = integration cost + storage cost • generates numerical predictions of syntactic processing • correspond to empirical data from reading time experiments • sentences presented and time taken to read each word • time taken to read each words corresponds with processing cost predicted by DLT • tonal pitch space theory (TPS): • both musicians and non musical have highly structured mental representation of musical pitch • quantifies tonal distance between 2 chords in musical sequence based on distance in structured cognitive space • “stable” pitches and chords perceived as closer to each other • separate keys perceived in orderly sets of distances from each other • numerical predictions of perceived tension • perceperception of tonal distance influences predicitions of the perceived ebb and flow of tension in musical sequences • tonal distance increases with tonal distance between chords • numerical predictions of TPS correspond to “tension profiling” scores produced by subjects who rate tension over time in a musical passage (listerners perceive musical elements in hierarchical relations) 2 Wednesday, March 9, 2016 • convergence of domain-specific cognitive theories • structural integration (connecting x to y) is a key part os syntactic processing integration depends on distance between x and y in abstract cognitive space • • activatoin based framework • x —> y activates representation of x (incoming input) and reactivates T (prior input) • shared integration resource • processing resources serve to rapidly and selectively bring low-activation representations up to activation threshold for integration to occur neural areas and operations shared • • integration takes place in distinct regions • corrresponding neural overlap • not yet known • required within subjects comparative studies of language and music using localization techniques design domain-independent tasks with two distinct levels of syntactic integration • demands (quantified with DLT and TPS operations) • use fMRI to search for brain regions which show increased activation as a function of integration cost in both domains • existing evidence for shared integration resource • language processing research (Kaan & Swab, 2002; Haarmann & Kolk, 1991) processing regions in frontal areas provide resources for computations in posterior • areas where syntactic representations reside • MEG data (Koelsch, et al., 2000 & 2001) • activation of Broca’s area in harmonic processing • ERP component analysis (Patel, et al., 2007) • domain-independent tasks elicited statistically indistinguishable P600s • evidence for sidtinct representation regions • cases of music-specific syntactic deficits (Griffiths, et al., 1997; Peretz, 1993 & 1994) • associated with damage to superior temporal gyri • thought to be important in long-term representation of harmonic relations • congenital amusia (Ayotte, et al., 2002) • due to a problem with fine-grained pitch discrimination • suggests developmental failure to form cognitive representations of pitch • linguistic priming: how processing is influenced by a word’s syntactic or semantic relation to a passage • harmonic priming: influence of harmonic context on the processing of a target chord due to the acoustic similarity and the its distance in the cognitive construct • regions of activation • shared resources • anterior cingulate and medial frontal cortex • Domain general attention mechanisms (Slevc and Okada, 2014) • speech specific activation • bilateral anterior temporal gyrus • supports implication in combinatorial semantic processing, NOT hierarchical structures (Wong and Gallate, 2012) • conflicting activation in broca’s area • differences in activation based on tasks • passive listening • discrimination task 3 Wednesday, March 9, 2016 • memory task • Music Task vs Passive Speech Listening Music discrimination – Passive speech listening • • No difference in activation of pars triangularis • Music memory – Passive speech listening • Greater activation of pars triangularis with music memory • reasoning for differences in activation • supporting Shared Synaptic Integration Resource Hypothesis overlapping activation seen when increased resources are need to complete the • speech or music task • Additional Support- cognitive control • Shared resources for linguistic and music processing in re-analyzing information and in conflict resolution (Slevc and Okada, 2014) • applications of SSIRH: improves treatments of speech disorders • Somatosensory Systems review figure 67c in Hendelman atlas • • modalities: • touch: discriminative, flutter vibration, crude touch • proprioception: where we are in space, muscle length and tension • temperature • nociception sensations of touch begin at the skin • • epidermis (outer layer) • dermis (inner layer) • mechanoreceptors • sense touch - mechxnosensitive ion channels • in organs - artery distension, stretch in digestive organs and bladder rapidly adapting: for discriminative touch • • fire at onset and offset of stimulus, not during • slowly adapting: for sensing steady pressure • fire the entire duration • types: • Pacinian corpuscles: in superficial subcutaneous layers, muscles, joints, internal organs • • end in nerve endings inside connective tissue • vibrations go through concentric layers to nerve endings to open mechanically gated ion channels • large receptive fields • rapidly adapting signal changes in pressure or sudden movement • • Meissner’s corpuscles: • superficial • inside connective tissue • 2 point discrimination • rapidly adapting 4 Wednesday, March 9, 2016 • small receptive fields • Ruffini endings: • deep skin layers • enlarged nerve endings • sense steady skin pressure (stretch, tension) • slowly adapting • large receptive fields Merkel’s disks: • • superficial • enlarged nerve endings • sense steady pressure • slowly adapting • free nerve endings • respond to mechanical, thermal or noxious stimulation • generally for nociception • two point discrimination • higher density of mechanoreceptors (in hands and face, especially fingertips) • small receptive fields more cortical tissue devoted to these areas • • may be special mechanisms • lateral somatosensory tissue: info from hands and face small receptive field large receptive field fast adaptation Meissner’s corpuscle Pacinian corpuscle slow adaptation Merkel’s disk Ruffini’s ending • muscle spindle: stretch receptor • senses muscle length - proprioceptors are the LARGEST and FASTEST conducting axons • proprioceptor mechanoreceptors are in joints AND information from the muscle • Golgi tendon organs send info about tension on a muscle • sensory info comes from muscles, which then feeds info back into the motor system • primary afferent axons Aa (group I): • • highly myelinated • largest (13-20 um) and fastest (80-120 m/s) • proprioception in skeltl muscles (because you need to be able to react quickly to where your body is in space • transmit to spinal cord from proprioceptive system • NOT present in skin • AB (group II): • large and myelinated (not as big as Aa) • 30-70 m/s • mechanical stimulus Pacinian corpuscles • • touch info from SKIN (mechanoreceptors) • Ad (group III) • small, myelinated 5 Wednesday, March 9, 2016 • 5-30 m/s • cold temperature fast pain information - sharp and localized • • C fibers (group IV) • small, unmyelinated • .5-2 m/s • mechanical stimulus - slow pain (dull aches) • temperature, itch dermatome: receptive fields - areas of the skin innervated by the left and right dorsal roots • • adjacent dorsal roots can innervate overlapping areas • demonstration: shingles • lesions or sores on skin activated on a specific nerve, so delineated within this area • pathways: • information sensed on skin, sent to spinal cord via fibers somatosensory info: • • from Pacinian corpuscles • less myelinated • cell bodies in dorsal root ganglion • information goes up spinal cord in dorsal columns to medulla and brainstem • collaterals also sent off for reflexive stimulation (in spinal cord) proprioceptive info • • highly myelinated • from muscle spindles • cell bodies in dorsal root ganglion • info goes up spinal cord in dorsal columns to medulla and brainstem • crosses in medulla • collaterals sent off for reflexive information • pain and temperature (via Ad and c fibers) • cell bodies in dorsal root ganglion • synapses in lamina of dorsal root • crosses immediately in dorsal horn and travels in contralateral side of spinal cord • spinothalamic pathway (aka anterolateral system) • somatotopic arrangement for information • lower extremities MEDIAL (Gracile fascicle) • sacral and lumbar • upper extremities lateral (cuneate fasciculus) • thoracic and cervical • in medulla, information synapses in gracile (lower) and cuneate nuclei (upper) • don’t have cuneate fascicles until thoracic level of spinal cord • cervical information enteres last • crosses midline in medulla, travels to thalamus • tactile pathway: • primary neurons from periphery (receptors) synapse in gracile or cuneate nucleus of medulla • dorsal columns in lower spinal cord are small, get bigger as you travel up the spinal cord • below medulla: dorsal columns - once above medulla pathway is called the medial lemniscus • secondary neuron: travels through pons and midbrain (brainstem) from medulla 6 Wednesday, March 9, 2016 • synapses in ventroposterior lateral nucleus of thalamus • once at level of medial lemniscus, ventral in medulla at pons, lemniscus moves more dorsally again • • at level of midbrain, lemniscus is not more lateral • now medial lemniscus and anterolateral systems travel together • tertiary neuron: from thalamus to primary somatosensory cortex • anterolateral system (ALS): spinothalamic tract • travels to ventral posterolateral nucleus of thalamus (VPL) crossed immediately in spinal cord • • pain information DIRECTLY to VPL • reticulothalamic: information from neurons that project to reticular nuclei (medullary or pons reticular system) • synapse in intralaminar nuclei of thalamus (centromedian and parafascicular) • underlie alterting mechanism to painful stimuli involved in arousal and sleep/wake cycles • • different modalities processed on different parts of the gyrus: • area 3B: • primary somatic sensory • dense inputs from VP • very responsive to somatic input electrical stimulation evokes sensory experiences • • lesions impair somatic sensation • area 3A: sense of body position • area 1: input from 3B (texture) • area 2: size and shape • posterior parietal: polymodal information • most inputs terminate in layer IV - projections to other layers (stacked in columns) • homunculus: mapping of receptive fields of SI neurons produces orderly organization of information • info from specific body area terminates in specific brain region • columns of neurons devoted to one particular receptor type • cortical map plasticity: • surrounding areas invade cortical areas that lose innervation • ex: remove a finger and the cortical areas for the fingers around it expand to fill the area • larger cortical areas for greater stimulation in periphery • spinocerebellar tract: on both sides • proprioceptive information from periphery to cerebellum • posterior: lower limb and trunk • cuneocerebellar: upper limbs • synapse in lateral cuneate nucleus • anterior: touch info to cerebellum • crosses twice • rostral: upper limb 7 Wednesday, March 9, 2016 Pain Systems pain: an unpleasant sensory and emotional experience associated with actual or potential • tissue damage or described in terms of tissue damage, or both • types of nociceptors: • free nerve endings of unmyelinated c fibers and lightly myelinated Ad fibers • mechanical: strong pressure (crude touch) • thermal: extreme temperature chemical: histamines (itch) and others • • polymodal • pain meds: target opioid system • pain stimulus: • release of various proteins/molecules - these act on nociceptors • bradykinin • potassium • prostaglandins • mast cells release cytokines in epidermis • pain receptors exhibit sensitization after injury (increase sensitivity - higher frequency of AP) • substance p causes vasodilation in blood vessels (why area around it gets red) • hyperalgesia: increased sensitivity after injury • pain receptors: sensitize after injury • lower threshold and more responsive (more AP) • allodynia: perceiving innocuous stimuli as painful after tissue damage • once area is injured, hurts (ex: blotting knee after scrape it painful) • involves vasodilation due to release of substance p • comparison of Ad and c fibers • Ad: lightly myelinated • first pain sensation registered (FAST) - signal initial pain response • pin prick • C fibers: unmyelinated • longer-lasting pain sensation (SLOW) • slow, dull, muscle pain • somatotopic organization of anterolateral system • lower extremities - lateral • upper extremities - medial • touch/proprioceptive information comes into dorsal spinal cord (crosses in medulla) • dorsal horn area: numerous lamina (layers) • pain information goes into different laminae (layers) in the dorsal horn • spinothalamic system - crosses immediately • pain info goes mainly to layer 1 and 5 • Ad: conduct pain and non-pain info (innocuous) • goes into layer I (posteromarginal nucleus) and V • c fibers into II (substantia gelatinosa) • most pain fibers synapse into substantia gelatinosa • non noxious stimuli synapse everythwhere • mostly in nucleus proprius (layer 3 and 4) • projections to other areas of the spinal cord • projections to thalamus 8 Wednesday, March 9, 2016 • projections to reticular system as well • gate theory: nociceptor sends pain info through c fiber • • when innocuous stimulus comes in from AB fibers which act on inhibitory neuron (via glutamatergic synapse) • laminae that receive inputs from Ad and C fibers also get input from AB fibers • non-nociceptive fibers indirectly inhibit the effects of the pain fibers • suppression of pain response this closes gate to transmission of stimuli (weakens signal sent to the thalamus) • • info sent to spinal cord in ALS or spinothalamic tract • anterolateral system (ALS): spinothalamic tract • travels to ventral posterolateral nucleus of thalamus (VPL) • crossed immediately in spinal cord • pain information DIRECTLY to VPL onto somatosensory cortex • • more important for pain perception and localization of pain • brainstem: reticulothalamic: information from neurons that project to reticular nuclei (medullary or pons reticular system) • separate - go into different nuclei of thalamus • synapse in intralaminar nuclei of thalamus (centromedian and parafascicular) underlie alterting mechanism to painful stimuli • • important for arousal to pain - alerting person to painful stimuli • involved in arousal and sleep/wake cycles • therapies for intractable (chronic) pain • thalamic lesioning (VPL, CM-PF nuclei of thalamus) • disadvantage to lesioning VPL: lose ALL somatosensory/proprioceptive information • better to lesion intralaminar nuclei - more specific for pain processing (fewer side effects) • deep brain stimulation in VPL • descending pain control: can selectively modulate pain in different areas • pain regulated by emotion and behavioral state • somatosensory cortex (ex: rubbing your knee makes it feel better) • insula and anterior cingulate • insula processes pain, addiction, reward information (also taste) • anterior cingulate: memories of pain • periventricular nucleus • periaqueductal gray (midbrain and pons) • fear conditioning (when lesioned, animals no longer freeze) • input from amygdala • lots of opioid receptors - stimulation can cause analgesia • raphe nuclei (in medulla) • serotonin production • these go down spinal cord and change pain sensations • section of spinal cord: • can lose pain and temp info on one side • somatosensory/proprioceptive on the other • pain perception involves cognitive processes • cortico-limbic striatal circuits: leads to autonomic reactivity • cognitive appraisal 9 Wednesday, March 9, 2016 • emotional reaction • behavioral response attention • • —>appraisal of pain determines painful output • pain neuromatrix: leads to thalamocortical relays • ACC, insula, PFC. amygdala, hypothalamus, sensory cortex • send descending info through the thalamus to ANS • leads to inflammatory and bimolecular mediators also leads to autonomic reactivity • • can also control descending pain modulation • activation of ANS leads to descending pain modulation (modulation of response of dorsal horn) • noxious stimulus leads to stimulation of nociceptor —> dorsal horn of the spine • leads to thalamocortical relays lots of plasticity in these areas • • activation of medial prefrontal cortex (mPFC) and posterior cingulate cortex (PCC) in pain rumination • looking at patients with chronic mandibular pain compared to controls • compared to controls, hyper activation in medial prefrontal cortex (goal directed behavior/ executive function), precuneus and PCC in those with chronic pain hyper-aware of pain • • plasticity has occurred in cortex to affect sensation of pain Visual System - Eye and Retina • primary visual cortex: striate cortex (projections from LGN) • lots of visual information processed in extrastriate areas • dorsal and ventral streams of visual processing (from extrastriate areas) • where sensory information comes together • properties of light travels in waves • • wavelength (determines frequency) • shorter wavelength - higher frequency (blue light) • longer wavelength - lower frequency (red light) • amplitude • light rays are refracted (bent) as they pass through a surface bends at perpendicular angle to surface that it is refracted by • • convex lens: converging or positive (shortens focal length) • brings a series of rays to CONVERGE a single focal point • distance from lens to this point is focal length • concave lens: lengthen focal length • scatters light theory used in glasses/contact lenses • • diopter: 1/focal length (reciprocal of focal length) • anatomy of the eye • cornea: encases anterior chamber filled with aqueous humor • concave - lots of refractive power (42 diopters - enough to get to the retina which is typically 2.4 cm behind it) 10 Wednesday, March 9, 2016 • nourished by aqueous humor and tear film • continually replenished canal of Schlemm: behind cornea • • holds vitreous humor • allows aqueous humor to flow through chamber • if blocked - fluid pressure buildup in anterior chamber—> glaucoma • lens : changes shape to bend light differently • does not have very much refractive power zonulas connect to ciliary muscles • • pupillary reflex • allows lens to flatten or round • ciliary muscles • contraction causes zonulas to flatten • sclera: white part encases vitreous chamber • • retina: sensory epithelium • contains photoreceptors • fovea: central part of retina • surrounded by macula • degradation here in macular degeneration - loss of central vision optic disk: where retinal ganglion cell axons exit the eye • • arteries and veins important for blood supply for the eye enter and exit here • blind spot - no photoreceptors • light enters the eye and focused on lens by the retina • refracted 2x - through cornea first and lens second • in order to see object, focal point must lie on the retina (light hits retina) • hits retina when lens is flattened (emmitropic) • photoreceptors on retina transduce light into electrical signal • accommodation: • changing the shape of the lens in response to distance of the object • zonulas: pull on lens (between ciliary muscles and lens) • acts in opposition to ciliary muscles • tightened zonulas and flattened lens for distance (ciliary muscles relaxed) • larger pupil • slackened zonulas and round lens for close (ciliary muscles contracted) • smaller pupil • constriction of pupils increases depth of focus (like changing aperture on camera) • emmetropia: lens flat and light rays focused on retina • pathway: important for focusing on objects as they change position • axons from retina a primary visual cortex to superior colliculus (in tectum of midbrain) • axons from superior colliculus to Edinger-Westphal nucleus (cranial nerve parasympathetic nucleus) and oculomotor nuclei (sending somatic information to for medial rectus contraction) • projection to ipsilateral oculomotor to ciliary and pupillary constrictor muscles • constriction of pupil and increases curvature of lens • ipsilateral oculomotor to medial rectus muscle (nasal side of each eye) • contraction of medial rectus results in convergence of the eyes to object of interest • parasympathetic component from Edinger-Westphal nucleus in brainstem 11 Wednesday, March 9, 2016 • just below tectum, deep within brainstem • send projections via oculomotor nerve to extra ocular muscles of eye (including medial rectus) • axons synapse in ciliary ganglia (to cause contractions in ciliary muscles of the eye) • oculomotor nuclei: • just below tectum • send projections via oculomotor nerve • send projections via oculomotor nerve to extra ocular muscles of eye (including medial rectus) • issues: • presbyopia: loss of accommodation (with age) • lens not at plastic, muscles don’t work as well • astigmatism: misshapen cornea • farsightedness: hyperopia focal point behind the retina • • to treat - need to shorten focal length • corrected with convex lens • nearsightedness: myopia • focal point in front of retina • to treat - need to lengthen focal length corrected with concave lens to scatter light • • retinal processing: • photoreceptors are the only sensitive cells in the retina • depolarize in dark • hyperpolarized by light • ganglion cells are the only source of output from the retina • retina: • laminar organization (3 layers) • ganglion cells • only cells that project out of the retina (out of optic disk through optic tract, ultimately to LGN) • some retinal ganglion cells that are sensitive to light - not involved in the regular circuitry • send signals back to retina • MOST inner layer in the retina • bipolar cells • inner nuclear layer • photoreceptors • sense light • most external in the retina • also horizontal and amacrine cells (these modify the signals) • light has to pass through all the cells before hitting photoreceptors (exception: fovea) • fovea: photoreceptors receive light directly • ganglion and bipolar cells pushed off to the side - light hits photoreceptors IMMEDIATELY • highest visual acuity • high concentration of cones (sense color) • fewer rods (for low light conditions) 12 Wednesday, March 9, 2016 • huge concentration in cones around fovea, increase in rods as you get closer to fovea but then sharp decrease in actual fovea multiple neurons CONVERGE onto single postsynaptic cell (in peripheral retina) • • 15-45 photoreceptors onto single bipolar neuron • exception: fovea - relationship is 1:1 (cones: retinal ganglion cells) • multiple bipolar cells synapse onto a single ganglion cell • photoreceptors: rods and cones • sensitive to light HYPERPOLARIZE in response to light most external in the retina - outer layer (at the back) • • embedded in pigmented epithelium (provides nutrients and processes molecules important for phototransduction) • glutamate is neurotransmitter • 4 regions • outer segment membranous disk with photopigments that absorb light • • inner segment • cell body • synaptic terminal • in darkness, tonically release glutamate onto the bipolar cells • visual pigments - opsins: rods have one: rhodopsin • • cones have 3 that are excited at different wavelengths • red: 560 nm • blue: 430 nm • green: 530 nm • phototransduction: • retinoid cycle in epithelium • rod in darkness • inactive rhodopsin • cGMP levels high • Na in (called dark current), K out • causes depolarization —> -40 mV • tonic release of glutamate onto bipolar neuron • rod in light: rhodopsin bleaching • light activates retinal (agonist for rhodopsin) and opsin (bleached pigment) • separation of opsin and retinal due to light • transducin activated (GPCR) —> causes decreased levels of cGMP (which gates Na) • caused by phosphodiesterase breaking down cGMP • Na channels close, K stay open • no more tonic influx of sodium —> hyperpolarization • membrane potential: -70 mV • decreased release of glutamate • termination: once stimulus is gone • activated rhodopsin (retinal) is phosphorylated • arresting binds rhodopsin and blocks activation of transducin 13 Wednesday, March 9, 2016 Retina to Cortex retina important for seeing contrast (differences in luminance) • • photoreceptors depolarized in dark - tonic release of glutamate onto bipolar • photoreceptors hyperpolarize in response to light • reduction in glutamate release • bipolar cells respond to glutamate • bipolar cells receptive field: area of the retina that when stimulated affects bipolar cells • • center and surround antagonistic: • on center bipolar cell • light in center: • horizontal cell releases glutamate onto photoreceptor terminals in center • photoreceptor hyperpolarized so releases glutamate onto ON bipolar cell • bipolar cell GPCR hyperpolarized —> removal of inhibition causes depolarization • light in CENTER is stimulus • if light in the surround, • off center • • indirect pathway: important when difference in luminance in surround • contributes to light adaptation • 2 types of bipolar cells • off: activation of glutamate receptor causes depolarization and AP • EPSP in darkness • dark is stimulus • on: hyperpolarize in response to glutamate (IN THE DARK) • light removes inhibition, which causes depolarization • GPCR respond to glutamate by CLOSING cGMP-gated channels —> HYPERPOLARIZATION • depolarization results from removal of inhibition • light is stimulus • horizontal cells mediate opposite effect of light on center vs. surround • get info from surrounding photoreceptors and synapse onto center photoreceptors • horizontal cells release GABA onto photoreceptor terminals • center surround passed on to the ganglion cells • light in center • cone is hyperpolarized • on center bipolar cell depolarized —> excited on center ganglion cell • off center bipolar cell hyperpolarized • dark in center • cone is depolarized • on center bipolar cell hyper polarized • off center bipolar cell depolarized —> excited off center ganglion cell • ganglion cells (only type in the retina that fire AP) • m type - magno (large) • 5% - small population of ganglion cells • larger receptive fields • rapid AP conduction 14 Wednesday, March 9, 2016 • are sensitive to low contrast stimuli (between light on retina) • NOT sensitive to color (no color processing) p type - parvo (small) • • 90% - most of ganglion cells • wavelength sensitive (COLOR) • medium and long wavelength (green and red) • nonM non P • wavelength sensitive (color) short wavelengths (blue) • • receptive fields: • sensitive to differences in illumination that occur within receptive field • concentric broad band cells (center surround antagonism) • respond best to differences in contrast within receptive field • off center cell: light in center - hyperpolarizes • • dark in center - depolarized, so fires AP • if dark in BOTH, still AP but reduced due to dark in the surround • moving dark stimulus: • dark in surround: hyperpolarization • as stimulus falls on center, increase in AP as entire receptive field covered, reduction in AP • • center surround organization of receptive fields leads to a response that emphasized contras at light dark edges • send axons out of eye via optic disk • color vision • cones have 3 opsins: blue, green and red (short - 430, medium - , long wavelengths) • cones sense color and report info to bipolar cells • probability that photon will be absorbed and activate phototransduction cascade in cones - varies by wavelength • color opponency: wavelengths perceived in combination • red vs green (long vs. medium) • opsins for these wavelengths on the X chromosome • reason for color blindness - in men these can be mutated and less likely to be cancelled out (because not another X chromosome) • on center red • red in center increases AP • red throughout field decreases AP (because overlap between red and green wavelengths) - decreased because of red light • surround cancelled ONLY by green • blue vs yellow (short vs. white) • coextensive single-opponent ganglion cells (detect blue/yellow) • information from s cones • inputs from s cones oppose combined inputs of long and medium cones throughout receptive fields • blue: short • yellow: NOT short, combination of red and green (long/medium) • **red and green light combine to make yellow** • opsins for medium and • retinal ganglion cells project to optic nerve 15 Wednesday, March 9, 2016 • nasal part of retina (closer to nose) • left sees left visual field right sees right visual field • • crosses in optic chiasm • temporal part of retina • left sees right visual field • right sees left visual field • stays ipsilateral synapses in LGN of thalamus • • LGN processes contralateral visual field info • projects to primary visual cortex (area 17, striate cortex, V1): • geniculocalcarine projections • OR optic radiations (aka Meyer’s loop) • 4 targets: LGN: perception • • hypothalamic suprachiasmatic nucleus: circadian rhythms • tectum: pupil and lens reflexes (accommodation) • oculomotor and Edinger-Westphal nuclei (contracts ciliary muscles) • superior colliculus: eye and head movement • superior colliculus: important for directing eye movement • • 2 functionally segregated layers • superficial: more sensory • input from retina ganglion cells and visual cortex (sensory info) • map of stimuli • outputs to thalamus • stratum griesum superficial (SGS) • stratum opticum (SO) • deep: for eye-directed movements • excitatory input from multimodal sensory, cortical and basal ganglia inputs (multimodal and motor) • inhibitory input from substantial nigra • map organizing orienting activity and stimulus selection • outputs to the brainstem gaze centers • stratum griesum intermediale (SGI) • stimulate superior colliculus • A: slow pursuit of stimulus • cells in superior colliculus fire prior to eye movement • B: quick saccade Visual Striate and Extrastriate ganglion cells on nasal portion cross in poetic chiasm - contralateral • • temporal stays ipsilateral • as you go up the visual hierarchy, receptive fields become more complex • receptive fields of photoreceptors: left and right hemifields • ganglion cells: center suround • concentric center/surround in LGN (primary visual cortex) 16 Wednesday, March 9, 2016 • bars: orientation and direction selectivity • after VI, some cells respond to objects, some to motion, etc LGN • • processes contralateral visual field • central portion of binocular vision important for depth perception • layered • ipsilateral eyes synapse in 2, 3 and 5 • contralateral eyes synapse in 1, 4 and 6 1 and 2 get info from magnocellular (larger cell bodies) • • 3-6 get info from parvocellular (smaller cell bodies) • koniocellular layers get info fro nonM non P cells (small areas between layers) • major source of excitatory inputs from primary visual cortex - function?? • also brainstem reticular system - involved in alertness and attentiveness • modulates LGN responses to visual stimuli calcarine sulcus (medial portion of occipital lobe) the most important area for vision • • bounded by primary visual cortex • parietooccipital sulcus • some layers binocular, some monocular • central retina: where vision is most accurate • binocular vision macular/foveal areas (because vision best here) • • monocular portions • outer retina (peripheral) • view inverted in primary visual cortex • portion of visual field processed in lower sulcus of primary visual sulcus • retinotopy: neighboring cells in retina send projections to the neighboring places in their target structures • often distorted because visual space not sampled uniformly by cells • central views magnified • image of light on retina activates many cortical neurons • when retina stimulated by light, activity in striate cortex is broad distribution with peak at corresponding retinotopic location • cytoarchitecture of striate cortex: 6 layers • layer 1: acellular • layer 2: many cell bodies • connection from layer 4 • extracortical connections • layer 3: many cell bodies • connection from layer 4 • extracortical connections • layer 4 is the most complicated (multiple sublayers) • main target of LGN neurons (layer 4C) - thalamic input • 4C divided into alpha and beta • 4B: mixing of info from both eyes —> FIRST BINOCULAR LAYER!!!! • layer 5: pyramidal cells • main outputs of cortex • layer 6: • pathways from retina to striate • magnocellular: 17 Wednesday, March 9, 2016 • motion/broad visual space, sensitive to contrast (not color) • object motion and guidance of motor actions starts with m ganglion cells in retina • • goes to magnocellular layers of LGN (layers 1 and 2) • ipsilateral retina to layer 2 • contralateral to layer 1 • —> layer IVC alpha (upper part of layer 4c) • —> layer IVB binocular areas • • —> layer 2-3 • —> binocular simple and complex, orientation and direction • parvocellular (interblob pathway) • detects shape • small receptive fields, but more of them analysis of small object shape • • starts with p type ganglion cells of retina • project to parvocellular layers of LGN (layers 4-6) • —>layer IVC beta • —> blobs/interblob layer II and III • NOT direction selective orientation selective (simple or complex) • • koniocellular (blob pathway) • analysis of color • monocular, lack orientation selectivity • starts with nonM non P type cells • go to koniocellular regions of LGN • —>directly to blobs of layer II and III (do NOT synapse in layer 4 like the others) • layer IV receptive fields • small, monocular, center-surround receptive fields • monocular neurons here clumped in columns (alternating inputs from either eye) • IVC alpha: color INSENSITIVE • info from magnocellular cells • IVC beta: color sensitive • info from parvocellular cells • ocular dominance columns: ONLY in layer IVC • receive input from ONE eye or the other • columns alternate between eyes • experiment: • inject radioactive proline into one eye • transported down axon to LGN, ultimately to cortex • inputs from each eye end up in alternating columns • blobs: process color information • monocular - input from EITHER eye (not both) • direct input from koniocellular layers of LGN and layer 4C • wavelength-sensitive (color information) • cytochrome oxidase blobs - mitochondrial enzyme as marker for cell metabolism • mainly in layers superficial to layer 4C - layers II, III • also in 4 and 5, but not as well known • blobs in rows within ocular dominance columns 18 Wednesday, March 9, 2016 • circular receptive fields (color opponent center-surround) • interblob layers 2 and 3 • • binocular processing • areas between blobs • simple and complex receptive fields • orientation and direction selective • most things outside blobs in layers 2-3 are binocular (input from both eyes, respond to stimuli from both) • cells in primary visual cortex respond best to bars of light • VI neurons outside layer IVC (superficial) • binocularity • orientation selectivity • cells respond best to certain orientation (optimal stimulus) does not respond at all to perpendicular bar • • responds (but less well) to orientations similar • most cells in VI outside IVC (except blobs) • respond best to bars • function of orientation selectivity: analysis of object shape • orientation columns direction selectivity • • respond best when bar of light move perpendicular to optimal orientation in one direction, but not the other • subset of orientation selective neurons (not all orientation selective cells are direction selective) • function: analysis of object motion • hypercolumn: 1mm squared • 360 degrees of orientation (changes about 20 degrees between columns) • inputs from either eye • blobs - colors • interblobs • superior colliculus: in midbrain • gets info from retinal ganglion cells and other sensory areas • map of the world around us • important for directing motion - eye and body movement • V1 on edges of calcimine sulcus • v2 and v3 outside those areas (extrastriate) • 2 streams of cortical processing in VI • some inputs from v1 goes directly to v2 and v3 • dorsal stream: • “where” pathway • motion and guidance of action control • broader spatial information • most inputs from magnocellular • direct projections from v1 • MT: middle temporal lobe • motor information • V5 receive input from V3, V2 and cells of layer IVB of striate • large receptive fields and direction selective - respond to motion 19 Wednesday, March 9, 2016 • MST: medial superior temporal • linear motion radial motion • • circular motion • navigation • directs eye movements and motion perception • ventral stream: • “what” pathway perception of world and recognition of objects • • more detailed information • parvocellular information • interblob and blob • most info processed in v2 and v3 • V4: inputs from blob and interblob regions orientation and color • • shape and color perception • Inferior Temporal (IT): • visual perception and memory • responds strongly to faces - facial recognition (some cells here ONLY respond to faces) grandmother cells/Jennifer Aniston cells: respond specifically to SPECIFIC faces • Parietal and Parahippocampal dorsal stream (dorsal relative to ventral stream) - “where” • • extensive representation of peripheral visual field • specializations for motion detection • spatial awareness and guidance of movement, navigation • spatial memory • comes mainly from m cells of retinal ganglion important areas: • • MT and MST important • injury to these areas can result in loss of motion detection • ex: will not perceive car in motion - see it as stationary • parietal lobe also important for understanding space • motion pathway (dorsal stream) M cells —> LGN • • LGN —> VI (orientation and direction selective) • VI —> middle temporal, v5 and medial superior temporal (MST) • MT: direction selective cells in columns • to visual motor areas of parietal love • speed and direction of motion perception of moving objects, maintenance of eye movements and guidance of • body through space • attention: • selectively processing simultaneous sources of information • concentrate on one at expense of others • benefits performance of behavioral tasks 20 Wednesday, March 9, 2016 • when paying attention, eyes directed to the task/object • study attention by examining behavioral manifestations ex: visual attention (saccade - rapid eye movement) • • motor manifestation of attention • spatial awareness: in humans, right parietal areas important • nonhumans are not as lateralized • parietal lobe: • superior lobe (aka post central gyrus): primary somatosensory information • • tactile perception, control of action • also may be involved in visuospatial attention (area 5) • intraparietal sulcus divides superior and inferior parietal lobe • inferior parietal: area 7 • visual/spatial recognition/awareness lateral intraparietal: edges of intraparietal sulcus • • reaching and grasping (hand-directed motion) • spatial attention: lateral sulcus • cells here fire AP before movement • responses here enhanced by attention (looking at object before moving it is helpful) ventral intraparietal (VIP): valleys of sulcus • • bringing sensory information together • visual, auditory and somatosensory brought together (deep sulcus) • experimenters record from lateral and ventral intraparietal • injuries to parietal lobe (DOES NOT IMPAIR visual process, but mental processing) • generally cannot judge spatial relations (size or arrangements) • neglect syndromes - people will ignore one side of their visual field • simultanagnosia: bilateral inability to see multiple objects at once • only attend to one object at a time • optic ataxia: impairment of visually guided reaching • affected hemifield is generally opposite lesion • inability to use visuospatial information to guide limb movements • hemispatial neglect: failure to notice objects in contralateral field of lesion • failure of attention or representation • injury to right parietal —> deficit in left visual field (and vice versa) • patients asked to draw a clock, will only draw one half of it • partial cortex lesions have different frames of reference - egocentric vs allocentric • ventral stream: “what” • visual patterns, colors, faces, object recognition • mainly comes from p and nonM nonP cells of retinal ganglion cells • areas • v1 • v2 • v3 • v4- info from v2 and v3 • IT (main area) - gets info from v4 • info from primary sensory cortex sent to V2 (blob and interblob information) • area V4 • sensitive to form and color 21 Wednesday, March 9, 2016 • achromatopsia: partial or complete loss of color vision • damage to V4 area IT • • object recognition/location • major output of V4 • LARGE receptive fields respond to a wide variety of colors and abstract shapes • includes foveal region • experiment: neurons in IT respond to faces certain cells respond only to faces, NOT to back of head, hand, etc • • about 10% of the neurons are specific for particular images • prosopagnosia: can’t recognize faces • no deficit in visual acuity or movement • functional organization of a memory system - lead to hippocampus • dorsal stream goes through parahippocampal cortex (PHC) WHERE • • ventral stream goes through perirhinal cortex (PRC) • WHAT • PFC – prefrontal cortex • hippocampus important for declarative memory in humans • inside temporal lobe - c shaped structure entorhinal cortex: last cortical stop before entering hippocampus • • perirhinal cortex • parahippocampal cortex • association areas of the cortex project to the medial temporal lobe • specifically parahippocampal region • very few direct inputs to the hippocampus • perirhinal cortex: • object recognition • ventral - what stream • parahippocampal in primates (postrhinal in rodents) • context, spatial cognition, navigation, object location • all info from PHC and PRC goes to entorhinal cortex • lateral - inputs from perirhinal • medial - inputs from postrhinal • subiculum: communicates with hippocampus • info pathway from cortex to hippocampus • ventral (what): • unimodal neocortical areas —> • perirhinal cortex —> • lateral entorhinal—> • CA3 and CA1 of hippocampus • dorsal (where) • polymodal neocortical areas —> • parahippocampal cortex —> • medial entorhinal —> • CA1 and CA3 of hippocampus • afferents and efferents of perirhinal cortex • inputs: various cortical areas • auditory 22 Wednesday, March 9, 2016 • gustatory • olfactory some visual (not as much as postrhinal) • • rostral PER gets somatosensory • multifeature stimuli processing • amygdala: for emotion • input for emotional salience incorporated into object processing • outputs: lateral entorhinal cortex • • cortex • basal ganglia • postrhinal cortex: mainly visual/spatial information from parietal areas • STRONG reciprocity • reciprocal connections with superior colliculus visual maps, motor outputs for gaze direction/eye movements • • inputs: • ventral temporal • posterior parietal • visual association areas • pulvinar nucleus of thalamus visual processing (not primary) • • superior colliculus • dorsal hippocampus • spatial processing • outputs: • medial entorhinal cortex • CA1 and dorsal subiculum • both entorhinal cortex sends info to hippocampus • projection: perforant path • lateral entorhinal (inputs from perirhinal) • in rodents important for object recognition • olfactory and somatosensory information (multimodal) • not much known in humans • medial entorhinal (inputs from postrhinal) • spatial info (grid cells - discovered by Mosers) • grid cells project to place cells in hippocampus • grid cells fire on triangular grid - where animal is in environment • fire at specific points in environment • place cells: as animal wanders, these cells fire when animal in specific area • fire at ONE specific point in environment • grid and place cells set framework of our spatial map • head direction • hippocampus: • in medial temporal lobe • looks like seahorse • part of the limbic system • roles in short term memory • HM study • roles in spatial 23 Wednesday, March 9, 2016 • rat hippocampus • subiculum gets inputs from perforant path (from entorhinal cortex) info then goes to dentate gyrus • • trisynaptic communication • dentate gyrus • CA1 • CA2 • 3 divisions: dorsal portion - spatial awareness/navigation • • posterior portion • ventral portion - emotional processing, HPA axis • long axis: septotemporal axis • orthogonal axis: transverse axis • can manipulate memory formation by lesioning hippocampus Memory Systems • multiple memory systems personal facts and emotions - episodic memory and emotional stored separately? (YES) • • Claparede patient: shook patient’s hand with pin, but she couldn’t say why • personal facts and skills - implicit memory and • sensory memory: very short (few seconds) - visual and sound • short term memory: • active contents of memory rapid access • • limited capacity • working memory: between sensory and long term (acts as retrieval for long term) • dysexecutive syndrome: pathology in frontal cortex - decrease in working memory AND executive function • often issues in retrieval long term • • slow access • inactive contents • unlimited capacity • explicit: declarative • conscious episodic • • very specific: where you were • located in hippocampus • where you WERE on a date • semantic • general knowledge about the world derived from episodic memory but different (effects of episodic memory - personal • experience) • located in middle frontal gyrus (possibly also in hippocampus) • some thing it’s all over the brain (assembling different components) • what happened in the world on a certain date • hippocampus, amygdala, rhinal cortex (mainly LIMBIC) 24 Wednesday, March 9, 2016 • implicit: non-declarative • skills/classical conditioning subconscious skill learning • • processed in cerebellum and basal ganglia • look at fMRI on slide 20 • procedural memory • conditioning/automated learning (reflexes) • priming negative: • • slow reaction time (Stroop color words test) • episodic retrival • positive: • speeds rxn time • conceptual: priming items of relating meaning (word fragment test) perceptual: priming items of relating form (word stem completion) • • studies: • word bank with “old” words - as subjects left, they subconsciously acted old (walked slower, slouched, etc.) - primed brain into thinking they were old • working memory with chimpanzee • HM: loss of explicit memory seizures localized in temporal lobe- bilaterally removed temporal lobe • • removed most of amygdaloid complex, hippocampus and parahippocampal gyrus (except for 2 cm caudal) • • reduced seizures, IQ increased slightly • deficits after surgery • no more declarative memory (anterograde amnesia) • some retrograde amnesia • short term memory OKAY, just long term affected • retained ability to learn new skills (kept skills 13 years later) • mirror tracing task • rotary pursuit task • incomplete pictures test • lost sense of smell • 3 stages of processing memory • encoding: getting information in • important for how well learned material remembered • located in hippocampus • storage: retaining information • sleep important • stored in cortex • retrieval: getting info out • deja vu: retrieval cues in current situation • uses hippocampus • reconsolidation: replaying a memory replaces original with slightly modified version • why eyewitness accounts so difficult • Alzheimers: most common neurodegenerative disorder in elderly • loss of memory and cognition


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