Binocular energy responses to natural images.

The binocular energy model provides a good description of the first stages of cortical binocular processing. Three important determinants of the responses of neurons under this model are the disparity of a stimulus, its spatial variation in disparity and its second-order luminance statistics. The influence of the latter two factors on the disparity tuning of the energy model were investigated. While each can have a significant effect on the energy response, neither presents a significant challenge when one considers the range of variation expected in natural images. The response of the energy model to natural binocular images was also investigated. The strongest responses were found for model neurons tuned to small disparities. This trend was more evident for vertical than for horizontal disparity, and flattened rapidly as image eccentricity increased. These results are predicted on the basis of simple geometrical considerations, and are reflected in both physiological and psychophysical measures of the disparity tuning of the visual system.