Contrast Gain Control in the Kitten's Visual System
Gary Sclar, Izumi Ohzawa, and Ralph D. Freeman (1985a)
Contrast gain control in the kitten's visual system.
J. Neurophysiol. 54: 668-675.
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We have studied the effects of contrast adaptation on cortical cells
from 4- and 6-wk-old kittens (49 and 47 cells, respectively) using
sine-wave grating stimuli. We wished to know if the effects of adaptation
to different contrast levels are more extensive than those in adult
animals. Our experiments involved adapting cells to different contrasts
(3.1, 12.5, and 50%) while concurrently measuring their contrast-response
functions at each of these different levels. We found qualitatively that
the effects of adaptation in the kitten are similar to those we have
previously documented in adult animals (19). Contrast-response functions
are laterally shifted along the log-contrast axis, effectively matching the
response range of the cells to prevailing contrast levels. The degree to
which this occurred varied from cell to cell. The average degree to which
cells showed these effects, as assessed both qualitatively and
quantitatively, was greater for kittens than for adult cats, and greater
for 4-wk-old kittens than for those aged 6 wk. This suggests that
susceptibility to adaptation varies as a function of age. Additional
studies were undertaken with the intent of localizing these adaptive
effects. First, lateral geniculate cells and fibers (n = 23) were studied
with our standard protocol, and second, we investigated the degree to which
the effects of adaptation of cortical cells transferred
interocularly. (ABSTRACT TRUNCATED AT 250 WORDS)