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
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
FEATURE ANALYSIS IN TOADS
interesting neuro-ethology subjects because of
highly selective (not merely sensitive) visual system
classify predator & prey signals
appropriate behavior
accessible visual system
FEATURE ANALYSIS IN TOADS
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
RECOGNITION & LOCALIZATION OF PREDATORS & PREY
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
RECOGNITION & LOCALIZATION OF PREDATORS & PREY
natural environment
feature detector neuron(s) selectively responsive specific stimulus does it work this way ?
p.97
fig.
4.1
RECOGNITION & LOCALIZATION OF PREDATORS & PREY
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
RECOGNITION & LOCALIZATION OF PREDATORS & PREY
natural environment
possible identified features of small invert. prey elongated shape movement parallel to body axis
used in lab experiments to study neural mechanisms
RECOGNITION & LOCALIZATION OF PREDATORS & PREY
prey-catching in the laboratory
hunger motivation to attempt prey capture
definition...
p.97
fig.
4.1
RECOGNITION & LOCALIZATION OF PREDATORS & PREY
prey-catching in the laboratory
glass cylinder
cardboard dummy stimuli 3 “worm” types rotated 20°/s
releasing value o / min direction
p.99 fig.4.2
RECOGNITION & LOCALIZATION OF PREDATORS & PREY
prey-catching in the laboratory
optimal dummy stimulus ? shape size (s) color contrast orientation thickness composition velocity p.99 fig.4.2
RECOGNITION & LOCALIZATION OF PREDATORS & PREY
prey-catching in the laboratory
worm stimulus releasing value ~ s
antiworm (= “amount”) releasing value ~ s
square biphasic ~ s (bugs predators ?)
p.100 fig.4.3
RECOGNITION & LOCALIZATION OF PREDATORS & PREY
prey-catching in the laboratory
worm variations releasers ? contrast orientation thickness composition direction
p.101 fig.4.4
RECOGNITION & LOCALIZATION OF PREDATORS & PREY
p.101 fig.4.4
prey-catching in the laboratory
worm variations releasers ? contrast orientation thickness composition direction
velocity
RECOGNITION & LOCALIZATION OF PREDATORS & PREY
prey-catching in the laboratory
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)
RECOGNITION & LOCALIZATION OF PREDATORS & PREY
prey-catching in the laboratory
toads respond to shape + direction response to
continuum ~ threshold not single feature
response ~ velocity more is better...
p.101 fig.4.4
RECOGNITION & LOCALIZATION OF PREDATORS & PREY
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
FEATURE ANALYZERS IN THE BRAIN
toad visual system
retina (vertebrates), 5 cell types receptor cells bipolar cells ganglion cells horizontal cells amacrine cells
FEATURE ANALYZERS IN THE BRAIN
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
FEATURE ANALYZERS IN THE BRAIN
toad visual system
retinal ganglion cell receptive fields space that excites or inhibits neuron activity
circular, 2 concentric regions center surround
FEATURE ANALYZERS IN THE BRAIN
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
FEATURE ANALYZERS IN THE BRAIN
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
FEATURE ANALYZERS IN THE BRAIN
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)
FEATURE ANALYZERS IN THE BRAIN
toad visual system
ganglion cells contralateral orderly maps retinotopic projections
optic tectum
thalamic pretectum (TP) p.105 fig.4.7
FEATURE ANALYZERS IN THE BRAIN
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
FEATURE ANALYZERS IN THE BRAIN
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
FEATURE ANALYZERS IN THE BRAIN
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
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field... eg, R3 cells p.107 fig.4.9
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field
p.107 fig.4.9
8° ERF IRF
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field
p.107 fig.4.9
8°
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field
p.107 fig.4.9
8°
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field
p.107 fig.4.9
8°
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field
p.107 fig.4.9
8°
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field
p.107 fig.4.9
8°
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field
p.107 fig.4.9
8°
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field
p.107 fig.4.9
8°
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field
p.107 fig.4.9
8°
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field
p.107 fig.4.9
8°
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field
p.107 fig.4.9
8°
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field
p.107 fig.4.9
8°
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
how do receptive fields ~ responses ? stimulus movement ~ receptive field
p.107 fig.4.9
8°
FEATURE ANALYZERS IN THE BRAIN
retinal ganglion cell responses to relevant stimuli
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
FEATURE ANALYZERS IN THE BRAIN
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