$ recognition & localization of predators & prey $ feature analyzers in the brain $ from recognition...
-
Upload
barnaby-carroll -
Category
Documents
-
view
219 -
download
0
Transcript of $ recognition & localization of predators & prey $ feature analyzers in the brain $ from recognition...
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