$ 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 PART 2: SENSORY WORLDS #10: FEATURE ANALYSIS IN TOADS II

$ thalamic-pretectal neuron responses to relevant stimuli $ many classes of neurons respond, but... $ no profiles ~ behavior... $ eg, TH3 cells p.109 fig.4.10 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 (R1  6) 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 $ timing $ magnetude $ what are the sources of T5(2) cell inputs ? of excitatory / inhibitory input 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 TH3T5(2) TP OT $ what about T5(2) feature analyzer output ? $ feedback loop  oscillator $ what would happen... ? FEATURE ANALYZERS IN THE BRAIN

$ neural circuit for feature analysis $ proposed connectivity T5(1) T5(2) TH3 OT TP $ let’s examine this hypothesis anyway... $ rationale not immediately clear 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

p.113 fig.4.13 $ neural circuit for feature analysis $ neuron firing in the hypothetical circuit (schematic) $ worm $ antiworm $ sm square $ lg square $ recall EFR & IFR FEATURE ANALYZERS IN THE BRAIN

p.113 fig.4.13 $ neural circuit for feature analysis $ PT inhibitory signals  OT for T5(2) response $ disrupt PT should block inhibition FEATURE ANALYZERS IN THE BRAIN

$ neural circuit for feature analysis p.114 fig.4.14 $ no lesion... intact PT $ lesion in PT $ 2 things happen to T5(2) response 1.no inhibition 2.selectivity lost 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 prey- catching $ 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 FEATURE ANALYZERS IN THE BRAIN

$ 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

$ adaptive motor response model p.116 fig.4.15 p.97 fig.4.1 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 FROM RECOGNITION TO RESPONSE

$ 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 SUMMARY: SENSORY WORLDS