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Binocular Deprivation
V
B
A
Test
C
Rearing
Ocular Dominance Histograms
Cortex
Binocular
Monocular
Binocular
IV
25
20
LGN
15
10
Eyes
5
0
1
2
3 4
binocular
Ocular Dominance
5
6
7
monocular
monocular
FIGURE 9.10 Response properties of visual cortex neurons in binocularly deprived cats. A. Both eyes
were kept closed until time of recording. B. The terminal stripes from each eye occupied a similar amount of
space. C. The majority of visually responsive neurons were driven by both eyes. (Adapted from Wiesel and
Wiesel, 1965)
Strabismus
V
A
B
C
Test
Cortex
Binocular
160
Monocular
Binocular
IV
120
LGN
80
40
0
1
2
3 4
binocular
Ocular Dominance
5
6
7
monocular
monocular
FIGURE 9.11 Response properties of visual cortex neurons in cats reared with artificial strabismus. A.
One eye was surgically deflected, such that a visual stimulus activated different topographic position on each
eye. Thus, cortical neurons were not activated by both eyes at the same time. B. The terminal stripes from
each eye occupied a similar amount of space. However, neurons outside of Layer IV did not receive conver-
gent input from both eyes. C. In strabismic cats, the vast majority of cortical neurons responded to either one
eye or the other. (Adapted from Hubel and Wiesel, 1965)
about 500 mm wide (Figure 9.5). Following monocular
deprivation, the LGN afferents from the nondeprived
eye come to occupy the majority of Layer IV, while
LGN afferents from the deprived eye occupy narrower
regions (Figure 9.9, middle panel). This suggests that
synapses from the nondeprived eye fail to undergo
their normal process of elimination. In contrast, a
greater than normal number of synapses from the
deprived eye must be lost.
The emergence of stripes does occur in cat cortex
during binocular deprivation over the first three post-
natal weeks. When the deprivation is extended into the
fourth postnatal week, the striping pattern begins to
deteriorate (Crair et al., 1998). Pattern vision is unnec-
essary for the segregation of thalamic afferents into
stripes, but maintenance of this striping pattern does
require normal visual experience. Surprisingly, thala-
mic afferents can segregate into a striping pattern even
when one or both eyes are removed (Crowley and
Katz, 1999, 2000). This was demonstrated in ferrets by
injecting a tracer directly into an eye-specific layer of
the LGN. When animals are enucleated, an afferent
striping pattern forms in the cortex with the same
dimensions found in control animals. While these
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