Abstract
Binocular vision fuses similar inputs from the two eyes into a single percept, whereas in- compatible inputs can produce rivalry, lustre, or diplopia. We measured neural responses to binocular stimuli with different phase relationships to test predictions from contemporary binocular combination models. Steady-State Visually Evoked Potentials (SSVEPs) were recorded from 15 observers in response to monocular and binocular stimulation at 3 Hz, using either On/Off or counterphase flicker with varied spatial and temporal phase rela- tionships. On/Off and counterphase flicker elicited responses at the expected fundamental frequency (3 Hz and 6 Hz, respectively) and their harmonics. Manipulating phase relation- ships modulated these response patterns, including a reduction in the fundamental amplitude for On/Off flicker. The data were modeled with a series of binocular combination algorithms, ranging in complexity from a simple linear sum to a two-stage binocular gain-control model with parallel monocular and binocular phase-selective channels. The model required paral- lel monocular channels to account for our data, whereas phase selectivity was not essential. Overall, the two-stage contrast gain-control model remains a powerful and flexible framework for describing binocular combinations across various experimental conditions and modalities.