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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 (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 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

TH3 T5(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)

TH3OT

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 inhibition2.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