Abstract
How the visual system combines information from the two eyes to form a unitary binocular representation of the external world is a fundamental question in vision science that has been the focus of many psychophysical and physiological investigations. Ding and Sperling (2006) measured the perceived phase of the cyclopean image as a function of the contrast ratio between two monocular sinewave gratings of the same spatial frequency but different phases, and developed a binocular combination model in which each eye exerts gain control on the other eye's signal and over the other eye's gain control. Critically, the relative phase of the two sinewaves plays a central role. We used the Ding-Sperling paradigm but measured both the perceived contrast and phase of cyclopean images in seventy-two combinations of base contrast, interocular contrast ratios, eye origin of the probe, and relative phase. We found that the perceived contrast of cyclopean images was independent of the relative phase of the monocular sinewave gratings, although the perceived phase of cyclopean images depended on the relative phase and contrast ratio of the monocular images. We modified the Ding-Sperling binocular combination model in two ways: (1) phase and contrast of the cyclopean images are computed in separate pathways, although with shared cross-eye contrast-gain control; and (2) phase-independent local energy from the two monocular images are used in contrast combination, after additional within-eye contrast gain-control. With five free parameters, the model yielded an excellent account of data from all the experimental conditions.
Supported by NEI, NSF of China.