Lecture 4 Flashcards
what are 5 possible types of binocular interaction or summation?
facilitation, complete summation, partial summation, no summation and inhibition
which category of binocular interaction/summation do normal binocular observers fall under?
partial summation
what is the degree of binocular interaction characterized by?
whether the binocular performance on a task (sensitivity for detecting contrast or an acuity target) is greater than, equal to or less than the performance of either eye alone
what is facilitation?
both eyes together is greater than the sum of the two individual eyes (both > L + R)
what is complete summation?
both eyes together are equal to the sum of the two eyes (both = L + R)
what is partial summation?
both eyes together are slightly less than the sum of the two eyes (Both < L + R, but > L or R)
what is no summation?
each eye functions on its own (both = L or both = R)
what is inhibition?
both eyes together is worse than each eye on its own (both < L or both < R)
what is probability summation or the independent theory?
simply by adding one more detector, you have 40% better chance of detecting a stimulus than one detector (no interaction between eyes)
what is neuronal summation or interaction theory?
when stimuli are synchronous in space and time - binocular vision is stimulated (much better chance of detection than predicted by statistics)
what are some examples of visual functions that show binocular summation?
threshold light detection, CFF (goes up), contrast threshold (goes down), resolution threshold (goes up), brightness and interocular transfer
how much does our contrast sensitivity function (CSF) improve from monocular to binocular? what happens to the threshold?
about 40% improvement and threshold goes down
what type of spatial frequency does contrast sensitivity function improve with binocular vs. monocular?
all spatial frequencies (low and high)
what happens to binocular contrast sensitivity with monocular blur?
binocular contrast sensitivity declines with increasing blur - with significant blur inhibition occurs
at what amount of retinal blur is binocular sensitivity worse than monocular?
more than +1.50D to +2.00D (why monovision patients may not be able to accept more than this difference in focus between both eyes)
what happens to critical flicker fusion frequency (CFF) with binocular summation?
the binocular percept is higher than with monocular - if it is in phase (out of phase will cancel)
what type of binocular interaction is occurring in low temporal frequency CFF?
facilitation
what type of binocular interaction is occurring in middle temporal frequency CFF?
complete summation
what type of binocular interaction is occurring in high temporal frequency CFF?
partial summation - light flickers so fast that binocular summation goes down
what type of binocular summation is seen in visual acuity testing?
partial binocular summation (binocular VA > monocular VA)
what happens to brightness when there are small interocular luminance differences?
they are averaged together
what happens to brightness when there are large interocular luminance differences?
leads to suppression of the dimmer eye (similar effect as monocular retinal blur: +10D)
what is the tilt aftereffect?
a visual illusion - fatiguing specifically tuned visual neurons monocularly
what is the interocular transfer of tilt aftereffect? (after fatiguing one eye and then viewing the target with the other eye)
the after effect isn’t as strong as viewing it with one eye - evidence for neurons receiving binocular input
