Abstract
Shape selectivity of V4 neurons for stimuli whose discrimination depends on V4 William H. Merigan, Department of Ophthalmology and Center for Visual Science, University of Rochester, Rochester, NY.
Purpose: To determine if V4 neurons show the requisite shape selectivity to mediate a discrimination that has been shown to depend on V4. Shape stimuli differed in geometric shape, but were matched in average luminance, contrast, orientation content, etc. ,Methods: The geometric shape stimuli consisted of a 4 x 4 arrays of oblique line segments, and thus, were closely matched in global properties. We tested discrimination of these stimuli by requiring monkeys to decide if successively presented stimuli were the same or different. The patterns were presented, under controlled fixation, at different locations in the visual field, such that the either first (sample) or second (test) stimuli of the comparison pair matched the location and size of the receptive field. An earlier study has shown that V4 lesions eliminated the ability of monkeys to discriminate these stimuli in this same testing paradigm. Results: Many V4 neurons showed moderate shape selectivity for the tested shape stimuli. The information in their response selectivity was sufficient to mediate correct discrimination based on the responses of only a few neurons. Conclusions: These results suggest that the discrimination of these shapes is dependent on neurons in area V4, and that these neurons have sufficiently selective responses to these stimuli to mediate the observed behavioral performance. Supported by EY 08898, and P30 EY01319 from NIH.