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PART 2: SENSORY WORLDS #10: FEATURE ANALYSIS IN TOADS II recognition & localization of predators & prey feature analyzers in the brain from recognition to response summary PART 2: SENSORY WORLDS #10: FEATURE ANALYSIS IN TOADS II recognition & localization of predators & prey feature analyzers in the brain from recognition to response summary FEATURE ANALYZERS IN THE BRAIN thalamic-pretectal neuron responses to relevant stimuli many classes of neurons respond, but... no profiles p.109 fig.4.10 ~ behavior... eg, TH3 cells FEATURE ANALYZERS IN THE BRAIN tectal neuron responses to relevant stimuli many classes of neurons respond T5(1) & (2) interesting T5(1) squares > worms T5(2) worms > squares each 20°- 30° of entire visual field p.110 fig.4.11 FEATURE ANALYZERS IN THE BRAIN tectal neuron responses to relevant stimuli T5(2) neurons also showed invariance with contrast velocity distance T5(2) are candidate prey-recognition neurons ~ same configural detection rules as behavior good eg of neural correlate of behavior FEATURE ANALYZERS IN THE BRAIN tectal neuron responses to relevant stimuli remaining questions about T5(2) neurons perform prey recognition function (addressed next time...) how are they wired into nervous system ? further evidence for proposed function ? FEATURE ANALYZERS IN THE BRAIN ganglion cells, contralateral projections OT & TP orderly maps retinotopic projections neuron classes (R16) p.105 fig.4.7 p.103 fig.4.5 FEATURE ANALYZERS IN THE BRAIN tectal neuron responses to relevant stimuli remaining questions about T5(2) neurons perform prey recognition function (addressed next time...) how are they wired into nervous system ? further evidence for proposed function ? FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis main determinants of neuron response properties of excitatory / inhibitory input timing magnetude what are the sources of T5(2) cell inputs ? FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis TP inhibition of T5(2) neurons in OT diagonal moving stimulus... p.111 fig.4.12 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis TP inhibition of T5(2) neurons in OT diagonal moving stimulus excitation p.111 fig.4.12 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis TP inhibition of T5(2) neurons in OT diagonal moving stimulus excitation + electrical stimulation of TP inhibition p.111 fig.4.12 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis TP inhibition of T5(2) neurons in OT diagonal moving stimulus excitation + electrical stimulation of TP inhibition remove electrical stimulation excitation p.111 fig.4.12 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis TP inhibition of T5(2) neurons in OT OT excitation of TP neurons (no details... reverse experiment likely did not give reverse results) p.111 fig.4.12 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis TP inhibition of T5(2) neurons in OT avoidance ? OT excitation of TP neurons orienting ? p.111 fig.4.12 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis connectivity possibilities TH3 TP OT T5(2) what would happen... ? feedback loop oscillator what about T5(2) feature analyzer output ? FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis proposed connectivity T5(1) T5(2) TH3 rationale not immediately clear let’s examine this hypothesis anyway... FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis recall response profiles of all 3 types of neurons TH3... (in TP) T5(1)... (in OT) T5(2)... (putative feature analyzers in OT) p.113 fig.4.13 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis consider the relative effects of a worm stimulus... TH3 does not inhibit T5(1) does excite T5(2) net effect... excited about worms p.113 fig.4.13 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis consider the relative effects of the antiworm... TH3 does inhibit T5(1) does not excite T5(2) not excited about the antiworm stimulus p.113 fig.4.13 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis consider the relative effects of the square... TH3 does inhibit T5(1) does excite T5(2) moderately excited about squares p.113 fig.4.13 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis neuron firing in the hypothetical circuit (schematic) worm antiworm sm square lg square recall EFR & IFR p.113 fig.4.13 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis PT inhibitory signals OT for T5(2) response disrupt PT should block inhibition p.113 fig.4.13 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis no lesion... intact PT lesion in PT 2 things happen to T5(2) response 1.no inhibition 2.selectivity lost p.114 fig.4.14 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis lesion in PT profiles of T5(2) firing (B) = behavior (C) p.114 fig.4.14 FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis increased responses to “inappropriate” stimuli termed disinhibition syndrome orienting & snapping at non-prey items: other toads experimenter own extremities FEATURE ANALYZERS IN THE BRAIN neural circuit for feature analysis T5(2) = feature analyzer neurons in preycatching further evidence inter- & intracellular recordings during behavior neurons fire while animals orient stimulate same neuron same orientation ok then... how do T5(2) neurons motor centers final section of chapter FROM RECOGNITION TO RESPONSE motor centers: bulbar-spinal region of brain OT (T5(2) & other) neurons project BS region stimulate BS region spike in T5(2) neurons* dye-fill T5(2) see projections into BS region * opposite to the normal direction of information flow... “antidromic” (?) FROM RECOGNITION TO RESPONSE adaptive motor response model sensory-motor interface: command-releasing systems (CRSs) made of command elements (CEs)... eg, T5(2) & TH3 motor program generators (MPGs) p.116 fig.4.15 FROM RECOGNITION TO RESPONSE p.97 fig.4.1 adaptive motor response model p.116 fig.4.15 FROM RECOGNITION TO RESPONSE adaptive motor response model specific responses of feature detector neurons behavioral experiments anatomical analyses of brain structures physiological analyses of PT & OT neurons initial concept incorrect... response not from single aspect of stimulus configuration of stimuli... sign stimuli ~ prey assemblies of filtering / triggering elements SUMMARY: SENSORY WORLDS input specialization conversion of physical stimulus neural signal acoustic fovea on basilar membrane in bat visual fovea in front of toad SUMMARY: SENSORY WORLDS receptive field of a neuron source of stimulus and/or representation on sensory surface (e.g. basilar membrane or retina) center/surround; excite/inhibit auditory difficult, achieved by neural processing essential aspect of receptive fields contrast SUMMARY: SENSORY WORLDS tuning sensory neurons respond to part of stimulus range many differently tuned neurons cover whole range achieves gain in sensitivity > broad tuned system SUMMARY: SENSORY WORLDS maps sensory world represented in brain map toad: retina tectum owl: auditory world ICX bat: distance/velocity profiles cortex 3 common features: topography: near-neighbor relationships preserved; tonotopy, retinotopy distortion: fovea overrepresented alignment: multimodal maps coincide SUMMARY: SENSORY WORLDS abstraction aspects of stimuli are perceived separately owl: timing & intensity processing bat: velocity & distance processing how are parts reassembled by the brain ? EMERGENT PROPERTIES REALIZED SUMMARY: SENSORY WORLDS feature analyzers some neurons respond to complex stimuli toad: T5(2) neurons & moving worm stimuli bat: cortex neurons & multiple harmonic echoes capture important aspects of behaviorally relevant stimuli SUMMARY: SENSORY WORLDS coincidence detection post-synaptic neuron responses to coincident temporal signals owl: left/right coincidence in nucleus laminaris; also includes concept of delay lines unique disparities encoded by multiple delay lines range of disparities represented in neural network SUMMARY: SENSORY WORLDS exam 1: R.2.22