Ocular dominance-dependent binocular combination of monocular neuronal responses in macaque V1

Primates rely on two eyes to see depth, while keeping a stable vision when one eye is closed. Although psychophysical and modeling studies have investigated how monocular signals are combined to form binocular vision, the corresponding neuronal mechanisms, especially in V1 where most neurons become binocular but with different eye preferences, are not well understood. Here we used two-photon calcium imaging to compare monocular and binocular responses of thousands of V1 superficial-layer neurons in three awake macaques. Under monocular stimulation, neurons preferring the stimulated eye responded substantially stronger than those preferring both eyes. However, under binocular stimulation, the responses of neurons preferring either eye were suppressed, and those preferring both eyes were enhanced, so that neuronal responses became similar regardless of eye preferences. A neuronally realistic model of binocular combination, which includes ocular dominance-dependent divisive interocular inhibition, and binocular summation, is proposed to account for these observations.