Toad features

Question 1

Retina optical images

Answer 1

Many different completely tiled images reach retina, different PRs/ paths parallel processing

Question 2

Vertical info flow Eye

Answer 2

PR -> Bipolar -> Ganglion
Forms center of RF

Question 3

Lateral info flow brain

Answer 3

Horizontal on PR and amacrine on BP cells inhibition
Forms surround of RF

Question 4

On Channel Visual

Answer 4

ALL PRs hyperpolar to light (DARK current)
On channel BP depolarize to light
Metabotropic Glutamate do inhibition on BP
Light = less NT from PR = less inhibition = depol to ON Gang, ON gang fires

Question 5

Off channel visual

Answer 5

ALL PRs hyperpolar to light (DARK current)
Off channel BP hyperpol to light
Ionotropic Glutamate do excitation on BP
Light = less NT from PR = less excitation = BP hyper pol onto Off gang, Gang less firing

Question 6

RF size and excitation

Answer 6

Excite more to light filling up center, start to inhibit once light in surround

Question 7

M cells Ganglion

Answer 7

Large RF, large objects and motion
Magnocellular layers of LGN

Question 8

P cells Ganglion

Answer 8

Small RF, fine detail and color
Parvocellular layers of LGN

Question 9

Visual pathway

Answer 9

Ganglions (nasal retinas cross optic chiasm)
LGN Thalamus - RETINOTOPIC, goes to V1
Hypothalamus (Suprachiasmatic nucleus)
Midbrain superior coliiculus (optic tectum), pretectum

Question 10

V1 Orientation Simple cells structure

Answer 10

Convergence of ROWS ON ON/OFF CELLS columns
RF elongated on an axis,
Selective for ORIENTATION, orientation tuning curve

Question 11

V1 Complex cell structure

Answer 11

Overlapping simple cells
INVARIANT to polarity and location
STILL ORIENTATION SELECTIVE
Good for form perception and object recognition

Question 12

What/Where pathways

Answer 12

What pathway - ventral, P ganglion, color/form, IT
Where pathway - dorsal, M ganglion, motion/space, MT

Question 13

IT selectivity

Answer 13

Feature analysis for faces
(prob not grandmother cells)
Critical features and invariance to other variation
Lesion IT = prosopagnosia/object agnosia
IT invariant for SIZE/POSITION/CONTRAST
INVARIANCE NEEDED FOR OBJ RECOG.

Question 14

Behavior of prey detection Toad

Answer 14

Can’t move eyes so must orient
Orient/approach prey
Binocular fixation
snap
swallow
wipe mouth
STREOTYPED FIXED ACTION PATTERN, once detect prey, will snap/swallow even if disappear

Question 15

Predator behavior toad

Answer 15

Avoidance, planting down and crouching

Question 16

What stimuli orient most to/least to and what invariant to

Answer 16

Worm-like, move in direction of elongation
Anti-worm, move in direction of short axis
Square - will orient if small, avoid if big square stimulus

Directional invariance = can move in any absolute direction, what matters is the RELATIVE direction
INVARIANT TO DIRECTION/SIZE/STRUCTURE/CONTRAST

Question 17

Size constancy in toads

Answer 17

Juvenile toads like a particular angular size, invariant to actual size
Adult toads HAVE SIZE CONSTANCY, preference for high angular size at short distance (big up close)

Question 18

Velocity feature toads

Answer 18

Higher stimulus velocity = more orienting turns
like faster
no change in response for anti worm movement

Question 19

Ganglion cell types Toads

Answer 19

3 sizes of RF, R2 (on) small center, R3 (on/off) medium, R4 (off) Big
Fire same for antiworm and big square, RETINA CONFUSES THE TWO, cant distinguish anti/square

Question 20

Two projections from retina toads

Answer 20

Thalamic Pretectum and Optic Tectum

Question 21

Thalamic Pretectum TH3

Answer 21

Prey feature analysis
Large RF, (R3/R4) input
Larger stimulus = more response
PREFERS ANTIWORM
Fires most to square

Question 22

Tectum cells

Answer 22

T5(1) and T5(2)
T5(1) fires most to square
T5(2) fires most to WORM

T5(2) good candidate for PREY-RECOG neurons
Firing correlates with behavior, worm, square, anti
Invariance to Contrast,velocity,distance

Question 23

Input to T5(2)

Answer 23

T5(1) EXCITES, TH3 INHIBITS
Worm = T5(1) excites, TH3 Low fire = low inhibit
Anti = little excite T5(1), TH3 fires and inhibits
Square - small = excite T5(1), low fire TH3 low inhibit
Square - big = low excite T5(1), high fire TH3 high inhibit

Question 24

Effects of Thalamic Pretectal lesion

Answer 24

Disinhibition Syndrome
Will orient to anti-worm!
If stimulate thalamus, will do avoidance respinse

Question 25

Recording in optic tectum

Answer 25

Record T5(2), have RF
T5(2) connected to motor center to orient
Connect to bulbar-spinal motor center medulla
Antero/retrograde tracer evidence
Antidromic spike = record T5(2) STIMULATE BULBAR, positive collision test is don’t see spike after antidromic (to right), negative if do see it, should have collided/cancel