feb 6 Flashcards
binocular neurons first found in
V1, then V2, V3, V4, V5
neurons needed for stereopsis and fusion must be __
binocular
model for how binocular neurons work
red neuron responds to crossed disparity; blue to uncrossed disparity; neither respond to 0 disparity
disparity-tuned neurons
respond when stimulus is presented simultaneously to non-corresponding points; each responds to narrow range of disparities; tuned excitatory/inhibitory neurons; depth magnitude
reciprocal neurons
near cells: show excitation to crossed disparity and inhibition to uncrossed disparity; far cells are opposite; depth order
near cells are ____ neurons that show ____ to crossed disparity and ____ to uncrossed disparity
reciprocal; excitation; inhibition
far cells are ____ neurons that show ____ to crossed disparity and ____ to uncrossed disparity
reciprocal; inhibition; excitation
binocular neurons (2) (and found where)
disparity-tuned neurons & reciprocal neurons found in V1 and V2
dorsal stream areas include _____, which process depth ___
V3a, hMT+, V7; magnitude
ventral stream areas including __ process depth __
LOC; order
absolute disparity (what, found where)
difference in distance of the image of an object from the fovea in each eye; mainly dorsal stream [hMT+/IPS]; may control vergence eye movements
relative disparity
difference in absolute disparities of 2 objects; mainly ventral stream; 3D shape perception and stereoacuity
visual cliff used to study
binocular vision in babies
visual cliff tells us that depth perception is present in human infants by __ months of age
6
babies don’t have ____ cuz their eyes don’t move together; eyes move together by ___ months
fusion; 3-4
to study stereopsis in human infants, babies wear ____ with ___ display on one side, and __ display on the other; _______ technique is used; stereopsis appears between _ and _ months
stereoglasses; flat; 3D; preferential looking; 3-5
stereoacuity
smallest amount of binocular disparity that can be detected; improves rapidly with age
maturation of stereoacuity
close to adult levels by 6 months; not fully mature until after 14
visual evoked potentials (VEPs)
electrical signals measured from scalp in response to visual stimulation
when do babies show adult brainwave pattern for random-dot stereogram using VEPs?
2-7 months
hypotheses for why stereopsis sudden
-vergence eye mvts becomes accurate (no)
-disparity-sensitive neurons in V1 mature (no)
-ocular dominance columns appear (no)
-disparity sensitivity in V2 matures (not sure)
-other aspects of V1 disparity-sensitive neurons mature (not sure)
T/F: vergence eye movements are essential for development of stereopsis
false
horopter vs panum’s area
horopter is imaginary line through fixation point; panum’s area is around horopter
monocular deprivation (what, caused by what)
brain does not receive stimulation from one eye; caused by a cataract in human infants
monocular deprivation results in ___
permanent poor visual acuity in deprived eye (amblyopia) and no stereopsis; shift in ocular dominance columns
what happens to ocular dominance columns when monocular deprivation occurs?
instead of alternating white and black stripes, most of V1 is driven by the functioning eye (e.g. more white, thin black stripes)
strabismus
less severe form of visual deprivation; misalignment of eyes (one eye fixates, the other esotropia/exotropia)
results of strabismus
2 eyes looking in different directions; fixated objects stimulate non-corresponding points in the 2 eyes
T/F: if develop strabismus as an adult, diplopia (double vision) occurs, but not when develop as a child
true
suppression scotoma
brain ignores parts of the retina where the diplopic image would fall
strabismus with interocular suppression
part of image from one eye ignored; often both eyes maintain good visual acuity; usually no stereopsis, relatively normal ocular dominance columns; few binocular neurons
similarities between effects of monocular deprivation vs strabismus (ocular dominance columns, monocular & binocular cortical neurons, visual acuity, stereopsis)
differences between effects of monocular deprivation vs strabismus (ocular dominance columns, monocular & binocular cortical neurons, visual acuity, stereopsis)
______ is an adaptive mechanism in people with strabismus to prevent double vision (diplopia)
interocular suppression
___ _____ image tends to be suppressed, but ___ exclusively
less salient; never
binocular rivalry
competition between two eyes for control of visual perception
rivalry and suppression occur for everything outside of ____
Panum’s Area
example of normal interocular suppression
suppressing nose
depth reversal illusion example
avocado pit or no pit
