recognition & localization of predators & prey feature analyzers in the brain

recognition & localization of predators & prey

feature analyzers in the brain

from recognition to response

summary

PART 2: SENSORY WORLDS#09: FEATURE ANALYSIS IN TOADS I

common toad – Bufo bufo order: Anura family: Bufonidae ~ 200 toad species

environment adaptable to climate prefer temperate & humid

reproduction patterns ~ rainfall species-specific mate calls

FEATURE ANALYSIS IN TOADS

prey insects, beetles, earthworms larger toads... birds, frogs

predators snakes, birds, carnivorous mammals

middle of the food chain sensory: predator or prey signal ? motor: appropriate behavior opposite responses to stimuli must be fast


interesting neuro-ethology subjects because of

highly selective (not merely sensitive) visual system

classify predator & prey signals

appropriate behavior

accessible visual system


vision

> auditory, olfactory, tactile senses

responses triggered by movement

RECOGNITION & LOCALIZATION OF PREDATORS & PREY

natural environment stereotypic responses to predator & prey distinguished using aspects of moving stimulus prey vs non-prey 4 types of response

orient (o) approach (a) fixate (f) snap (s)

p.97

fig.

4.1


natural environment

FAP ?

innate responses naïve animals do it...

linked action patterns only o-a-f-s sequence ?

sign stimuli ?

releasing mechanism ? p.97

fig.

4.1


natural environment

feature detector neuron(s) selectively responsive specific stimulus does it work this way ?

p.97

fig.

4.1


natural environment

not rigid linked o-a-f-s sequence

different stimulus different response sequence eg: prey @ constant distance o-o-o-o-o-o...

(lab experiment) ~ distance & movement

no behavioral prerequisites

not true FAP p.99 fig.4.2


natural environment

possible identified features of small invert. prey elongated shape movement parallel to body axis

used in lab experiments to study neural mechanisms


prey-catching in the laboratory

hunger motivation to attempt prey capture

definition...

p.97

fig.

4.1



glass cylinder

cardboard dummy stimuli 3 “worm” types rotated 20°/s

releasing value o / min direction

p.99 fig.4.2



optimal dummy stimulus ? shape size (s) color contrast orientation thickness composition velocity p.99 fig.4.2



worm stimulus releasing value ~ s

antiworm (= “amount”) releasing value ~ s

square biphasic ~ s (bugs predators ?)

p.100 fig.4.3



worm variations releasers ? contrast orientation thickness composition direction

p.101 fig.4.4


p.101 fig.4.4


worm variations releasers ? contrast orientation thickness composition direction

velocity



toads respond to shape + direction in variety of conditions invariance recognition robust informs about releasing mechanism relationship critical configural property emergent (whole > sum of parts)



toads respond to shape + direction response to

continuum ~ threshold not single feature

response ~ velocity more is better...

p.101 fig.4.4


toad visual system

retina (vertebrates)

optic nerve contralateral

optic tectum

thalamic pretectum (TP) (fewer projections)

p.103 fig.4.5

FEATURE ANALYZERS IN THE BRAIN

toad visual system

retina (vertebrates), 5 cell types receptor cells bipolar cells in series ganglion cells horizontal cells amacrine cells


toad visual system

retina (vertebrates), 5 cell types receptor cells bipolar cells ganglion cells horizontal cells amacrine cells


toad visual system

retina (vertebrates), 5 cell types receptor cells: input elements, transduce light

rods cones

bipolar cells: relay elements ganglion cells: output brain via optic nerve horizontal cells amacrine cells

lateral interactions with retina


toad visual system

retinal ganglion cell receptive fields space that excites or inhibits neuron activity

circular, 2 concentric regions center surround


toad visual system

retinal ganglion cell receptive fields

space that excites or inhibits neuron activity

circular, 2 concentric regions center: excitatory (ERF) surround: inhibitory (IRF)

p.104 fig.4.6


toad visual system

retinal ganglion cell receptive fields

space that excites or inhibits neuron activity

circular, 2 concentric regions center: inhibitory (IRF) surround: excitatory (ERF)

p.104 fig.4.6


toad visual system

retinal ganglion cell receptive fields space that excites or inhibits neuron activity

circular, 2 concentric regions center surround

retinal ganglion cells distinguished by position (lateral axis) IRF & ERF strengths (longitudinal axis)


toad visual system

ganglion cells contralateral orderly maps retinotopic projections

optic tectum

thalamic pretectum (TP) p.105 fig.4.7


toad visual system

ganglion cells contralateral orderly maps retinotopic projections neuron classes R1-6 different layers

optic tectum

thalamic pretectum (TP) p.103 fig.4.5


retinal ganglion cell responses to relevant stimuli neurons that respond (spike) differentially ? prey recognition neurons / families of neurons ? extracellular recordings 6 neuron classes (R1 R6) early findings, center ERFs:

R2: 4° R3: 8° R4: 16°

no stimulus quality info... p.106 fig.4.8


retinal ganglion cell responses to relevant stimuli

no classes of neurons respond ~ behavior... no response ~ long axis of stimulus no worm preference antiworm ~ square

p.107 fig.4.9



how do receptive fields ~ responses ? stimulus movement ~ receptive field... eg, R3 cells p.107 fig.4.9



how do receptive fields ~ responses ? stimulus movement ~ receptive field

p.107 fig.4.9

8° ERF IRF



how do receptive fields ~ responses ? stimulus movement ~ receptive field

p.107 fig.4.9

8°



how do receptive fields ~ responses ? stimulus movement ~ receptive field... logic works for R2 & R4 does not find feature analyzers in brain

p.107 fig.4.9


recognition & localization of predators & prey feature analyzers in the brain

Documents

toads prey insects

prey capture definition

s bugs predators

frogs predators snakes

s releasing value o

constant distance oo

s antiworm

rigid linked o