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Flashcards in Vision Deck (11):

how do we perceive unified world

perception based on pattern and freq with which a limited number of specialized receptors fire, in conjunction with expectations and previous experiences


path from eye to brain

light enters eye via pupil
cornea projects to retina at back of eye
retina lined with photoreceptors
photoreceptors are sensory neurons stimulated by light
no picture hits retina, just light frequencies


retina is upside down and backwards

light from above hits bottom of retina and vice versa; from right, hits left, etc.


types of retinal cells

ganglion: all info passes through ganglion to brain
these 4 interneurons are all in front of retinal cells. light needs to pass thru pupil, lens cornea, vitreous humor then through interneurons



center of retina
little dip where there are no interneurons covering retinal cells
light hits photoreceptors almost directly
vision from fovea is very acute and detailed
don't perceive that vision is different
if something moves in front of you you move your eyes and head...trying to get it into fovea



black and white
active in dim light
more 20x rods than cones
not on fovea
peripheral vision
more sensitive to light....need less to send message
if lose rods, you are night blind
not interpreted as color
look at stars on an angle, will see better with periphery that need less light



higher acuity
day vision
color vision
better temporal resolution
detect movement better
3 types: red (long 558), green (med 530) blue (short 420) - maximum response to these freq; less to other freq
need a lot of light or will not send message
won't send message in dark
have a lot in fovea
also some scattered elsewhere



chemicals that change in response to light
each type of rods and cones needs different photopigment



when not struck by light, contains 11-cis-re
tinal. made from vitamin A.
in light, changes to all-trans-retinal
need this to be sensitive to light
do not make vitamin A, get it from diet
really need carrots


young-helmholtz theory

trichromatic theory of light


what happens when light comes on?

11-cis-retinal changes to all-trans-retinal.
also have a lot of cGMP in photoreceptors
causes sodium ion channels to close
sodium stops moving
cell becomes hyper polarized
releases inhibition on interneurons
thus light photoreceptors STOP firing