none of the behavioral components are a necessary prerequisite for the others to occur: they are independent “FAPs”

If these are FAPs in the true sense the lets find what controls its: •Step 1 Find cell/s that recognize prey

Behavioral components of prey capture in the frog

1

2

3

4

1

2,3

4

Laboratory analysis of innate orientation behavior of toad to varying stimuli

•Toad in glass jar above turntable•Turntable used to pass targets in front of toad

Results: •Toad optimally responds to “worm-like” stimuli•Worm must move along long axis but can move in any direction•Orientation responses to worm are consistent FAPs “they are invariant.”

Sensory transduction: the eye

Sensory transduction: the retina

Optic nerve (blind spot)

Ganglion cell

Horizontal cells

Amacrine cells

Bipolar cells

Rods and cones(toads rods only)

Sensory transduction: the retina

Synaptic interactions of bipolar, horizontal and amacrine cells produce center surround fields in ganglion cells

Results from intracellular recordings

Vertebrate ganglion cells in general can be classified into two types•On-center/off-surround•Off-center/on-surround

•Additionally, some are sensitive to movement in their field

The retina is a matrix of overlapping center/surround fields of ganglion cells

Neurophysiological method:•Animal placed on stage •Electrodes placed in specific neuropil•Stimulated visually while recording from cells

Results 1:Retinal ganglion cells can be typed based on response type based on size of receptive field:

•R2 4 degrees •R3 8 degrees •R4 16 degrees

-no ganglion cell matched behavior

The search for the cell/s that recognize prey features

Visual pathway in the toadOptic nerve crosses at the optic chiasm and projects contralaterally to:

•Optic tectum •Pre-tectum of the thalamus

Retinotopic organization is maintained in both these regions

Example of Retinotopy from the Macaque visual system

A flickering stimulus Retinotopic representation in layer 4C of V1

Tootell et al (1988a).

Retinotopic organization is maintained in both these regions

Thalamus

Cross sectional reference

Results 2: Thalamic pretectal TH3 cell responses to test stimuli•Small receptive fields•Responsive to moving stimuli•Collectively (as a population) map visual field •Do not correlate to behavior- are not prey detectors

The search for the cell that recognizes prey

The search for the cell that recognizes prey

The T5 cell integration of worm features: •Size•Shape•Movement •2 types defined by different response profiles

T5(2) cells in particular produced invariant responses across changes in a number of parameters:

•Contrast•Velocity •Distance •So long as the worm-like stimulus moved along its long-axis

The T5(2) response: Putting it all together

T5(1)

TH3

T5(2)+

-Output

Antatomical and physiological organization of TH3, T5(1) and T5(2) cells

Output options:

1) T5(1) HIGH/ TH3 LOW = T5 (2) HIGH

2) T5(1) HIGH/TH3 HIGH = T5(2) CANCELED

3) T5(1) LOW/TH3 LOW = T5(2) NO INPUT/CANCELED

4) T5(1) LOW/TH3 HIGH = T5(2) INHIBITED

T5(1)

TH3

T5(2)+

-Output

So what do you predict would happen behaviorally and in terms of T5(2) cells if you cut the output from TH3 to T5(2)?

Pre leison

TH3 lesion