Ocular Dominance Predicts Neither Strength nor Class of Disparity Selectivity with Random-dot Stimuli in Primate V1

We address two unresolved issues concerning the coding of binocular disparity in primary visual cortex. Experimental studies and theoretical models have suggested a relationship between a cell's ocular dominance, assessed with monocular stimuli, and its tuning to binocular disparity. First, the disparity energy model of disparity selectivity suggests that there should be a correlation between ocular dominance and the strength of disparity tuning. Second, several studies have reported a relationship between ocular dominance and the shape of the disparity tuning curve, with cells dominated by one eye more likely to have disparity tuning of the tuned-inhibitory type. We investigated both of these relationships in single neurons recorded from the primary visual cortex of awake fixating macaques, using dynamic random-dot patterns as a stimulus. To classify disparity tuning curves quantitatively, we develop a new measure of symmetry, which can be applied to any function. We find no evidence for any correlation between ocular dominance and the nature of disparity tuning. This places constraints on the circuitry underlying disparity tuning.