Development of binocular vision in the kitten's striate cortex.
Citation Info
Ralph D. Freeman, and Izumi Ohzawa (1992)
Development of binocular vision in the kitten's striate cortex.
J. Neurosci. 12: 4721-4736.
Abstract
Studies of the development and plasticity of the visual pathway are
well documented, but a basic question remains open: what is the
physiological status of the system prior to extensive visual experience?
Somewhat conflicting answers have been put forward, and in a major area,
binocular vision, reports have ranged from severe immaturity to
well-developed maturity. This is an important question to resolve since
binocular cells in the visual cortex are thought to be the neural substrate
for stereoscopic depth perception. We have addressed this question by
recording from single cells in the striate cortex of kittens at postnatal
ages 2, 3, and 4 weeks and from adults for comparison. Gratings with
sinusoidal luminance distribution are presented to left, right, or both
eyes. For each cell, we determine optimal values for orientation and
spatial frequency. Relative phase (retinal disparity) is then varied in a
dichoptic sequence so that binocular interaction may be studied. Results
are as follows. In the normal adult, we have shown in previous work that
most binocular interaction in the visual cortex can be accounted for on the
basis of linear summation. Results from 3 and 4 week postnatal kittens are
closely similar to those from adults. All types of binocular interaction
found in adults are present in kittens. This includes phase-specific and
non-phase-specific suppression or facilitation. Furthermore, monocular and
binocular tuning characteristics are comparable in kittens and adults. The
clear changes that occur with age are optimal spatial frequencies and peak
responses. In addition, at 2 weeks, there is a substantially higher
proportion of monocular cells compared to other ages and correspondingly,
lower relative numbers of cells that exhibit phase-specific or suppressive
binocular interactions. From increases in optimal spatial frequency and
interpupillary distance with age, we calculated predicted changes in
binocular disparity thresholds (stereo acuity) with age. Although there are
methodological limits with respect to the behavioral testing of young
kittens, the predicted results are comparable to some of the values
obtained. Considered together, our results show that the physiological
apparatus for binocular vision is functional at an early stage in postnatal
development. It is possible that the connections that underlie this
function are developed rapidly during early postnatal experience. An
alternative possibility is that there is an elaborate genetic organization
of binocular vision, but our study does not address this issue directly. A
combination of these factors may be applicable.(ABSTRACT TRUNCATED AT 400
WORDS)