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Flashcards in vision 3 Deck (20)
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1
Q
Retinal ganglion cells have donut-shaped receptive fields and come in two opposite types:
A
1. "ON" center ganglion cells
2. "OFF" center ganglion cells
2
Q
“ON” center ganglion cells –
A
excited by light shining in their centers and inhibited by light in the periphery
3
Q
“OFF” center ganglion cells
A
excited by light shining in their periphery and inhibited by light shining in their centers
4
Q
In the fovea, a ganglion cell receptive field center _____.
A
may be only as wide as a single cone, with an atagonistic surround not much bigger
5
Q
Receptive fields are larger _____
A
in the periphery of the retina.
6
Q
The receptive field surround is mediated by:
A
horizontal cells
7
Q
Horizontal cell function
A
1. behave as though they have excitatory receptors for glutamate released from photoreceptors
2. make inhibitory synapses on neighboring photoreceptors in the field center
8
Q
when horizontal cells are excited by glutamate, they
A
release GABA to inhibit neighboring photoreceptors in the receptive field
9
Q
The key determinant in the receptive field type of ganglion cells is ____
A
The type of receptor on bipolar cells.
10
Q
Light's effect on photoreceptor cells
A
Light hyperpolarizes photoreceptor cells and leads to a decrease in NT release
11
Q
photoreceptor cells release
A
glutamate
12
Q
Bipolar cells can be:
A
1. excited (OFF-center)
2. inhibited (ON-center)

by glutamate, it just depends on the receptor type
13
Q
bipolar cells always make ____ on ganglion cells
A
excitatory synapses
14
Q
Ocular dominance is a
A
measure of the relative synaptic input to a cell from each eye
15
Q
Monocular deprivation:
A
1. kittens 1 eye closed for several days during critical period, lose all connections to deprived eye
2. the longer the deprivation, the worse the damage
3. even if eye is re-opened, damage doe not recover
4. once the connections are lost, they are gone for good.

16
Q
Monocular deprivation experiment illustrates that
A
While connections are genetically determined, they are not immutable, at least for a while after birth (sensitive period).

These results suggest the explanation known as “disuse” atrophy, or “use it or lose it”.
17
Q
Binocular deprivation:
A
1. deprive kitten of sign in both eyes
2. normal primary cortex
3. there were more non-responsive cells, but most cells could be driven, and most were binocular.
4. half of cells had normal receptive field
5. BUT cats were behaviorally blind with higher order visual cells completely disrupted
18
Q
Binocular deprivation experiment illustrates that
A
something is happening that involves an interaction—perhaps competition—between the two eyes.
19
Q
Alternating monocular deprivation:
A
1. One eye is deprived and then reopened
2. No cortical cells can be driven by the deprived eye
3. BUT if the other eye is then deprived, the re-opened eye recovers and the newly deprived eye loses its connection with the cortex
20
Q
Alternating monocular deprivation illustrates that
A
the competition—active suppression by the active eye—that occurs between converging inputs from each eye in the cortex.