ON THE NEUROPHYSIOLOGICAL ORGANIZATION OF BINOCULAR VISION

The considerable mixing in the visual cortex, of signals from left and right eyes, provides an abundant population of binocularly activated neurons. Based on this and on the fact that cortical cells respond best to different ranges of retinal disparities, it has been proposed that these neurons form the physiological substrate of stereoscopic depth discrimination. We outline reasons here for addressing first the more fundamental issue of the rules of convergence in the visual cortex, for input from the two eyes. We show that most of this convergence may be described by a linear summation process. However, there is a nonlinear mechanism that maintains binocular interaction regardless of large differences in stimulus strength between the eyes. This finding suggests that a cell which appears to be dominated by one eye, when monocular tests are conducted, may respond equally under binocular conditions. In this case, binocular processing for all cortical cells could be uniform and independent of the ocular dominance values determined monocularly. With respect to a neural mechanism for the processing of information concerning different depths in space, we propose an alternative to the conventional notion. First, we identify fundamental problems with the current view. Second, we describe a procedure which allows us to distinguish between the conventional view and our alternative proposal. Standard receptive field mapping techniques are not adequate for determining phase-disparity relationships of the type we require. Therefore, we have employed a reverse correlation procedure which enables efficient and detailed mapping of receptive field structure. Third, we describe preliminary data concerning the physiological mechanism of stereoscopic depth discrimination. © 1990.