Encoding and estimation of first- and second-order binocular disparity in natural images

•First- and second-order responses to natural binocular images are correlated.•Second-order mechanisms can improve the accuracy of disparity estimation.•Second-order mechanisms can extend the depth range of binocular stereopsis.

The first stage of processing of binocular information in the visual cortex is performed by mechanisms that are bandpass-tuned for spatial frequency and orientation. Psychophysical and physiological evidence have also demonstrated the existence of second-order mechanisms in binocular processing, which can encode disparities that are not directly accessible to first-order mechanisms. We compared the responses of first- and second-order binocular filters to natural images. We found that the responses of the second-order mechanisms are to some extent correlated with the responses of the first-order mechanisms, and that they can contribute to increasing both the accuracy, and depth range, of binocular stereopsis.