Toad features Flashcards
Retina optical images
Many different completely tiled images reach retina, different PRs/ paths parallel processing
Vertical info flow Eye
PR -> Bipolar -> Ganglion
Forms center of RF
Lateral info flow brain
Horizontal on PR and amacrine on BP cells inhibition
Forms surround of RF
On Channel Visual
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
Off channel visual
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
RF size and excitation
Excite more to light filling up center, start to inhibit once light in surround
M cells Ganglion
Large RF, large objects and motion
Magnocellular layers of LGN
P cells Ganglion
Small RF, fine detail and color
Parvocellular layers of LGN
Visual pathway
Ganglions (nasal retinas cross optic chiasm)
LGN Thalamus - RETINOTOPIC, goes to V1
Hypothalamus (Suprachiasmatic nucleus)
Midbrain superior coliiculus (optic tectum), pretectum
V1 Orientation Simple cells structure
Convergence of ROWS ON ON/OFF CELLS columns
RF elongated on an axis,
Selective for ORIENTATION, orientation tuning curve
V1 Complex cell structure
Overlapping simple cells
INVARIANT to polarity and location
STILL ORIENTATION SELECTIVE
Good for form perception and object recognition
What/Where pathways
What pathway - ventral, P ganglion, color/form, IT
Where pathway - dorsal, M ganglion, motion/space, MT
IT selectivity
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.
Behavior of prey detection Toad
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
Predator behavior toad
Avoidance, planting down and crouching
What stimuli orient most to/least to and what invariant to
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
Size constancy in toads
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)
Velocity feature toads
Higher stimulus velocity = more orienting turns
like faster
no change in response for anti worm movement
Ganglion cell types Toads
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
Two projections from retina toads
Thalamic Pretectum and Optic Tectum
Thalamic Pretectum TH3
Prey feature analysis
Large RF, (R3/R4) input
Larger stimulus = more response
PREFERS ANTIWORM
Fires most to square
Tectum cells
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
Input to T5(2)
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
Effects of Thalamic Pretectal lesion
Disinhibition Syndrome
Will orient to anti-worm!
If stimulate thalamus, will do avoidance respinse
