This study investigates extra-receptive field (extra-RF) contextual modulation in area V1 of awake, behaving macaque monkeys. Extra-RF contextual modulation refers to the modulation of V1 neuron activity by stimuli outside the neuron's receptive field (RF). The study used texture displays to examine how contextual modulation is influenced by disparity, color, luminance, and orientation cues. The results show that contextual modulation has a spatial extent of approximately 8 to 10 degrees parafoveally and is correlated with perceptual experience of binocularly rivalrous texture displays and surface occlusion. The modulation occurs with a latency of 80-100 milliseconds after stimulus onset, potentially allowing feedback from extrastriate areas to underlie this effect. The study also examined the effects of various visual cues on extra-RF contextual modulation. The results show that contextual modulation is evoked by a wide range of cues, including binocular disparity, color, luminance, and orientation. The modulation is not limited to any particular cue, suggesting that it serves an integrative function across diverse cues. The spatial extent of extra-RF modulation was also studied, and it was found to decline with increasing disc diameter, vanishing at approximately 10 degrees diameter. The study also examined the effects of binocular rivalry on extra-RF contextual modulation. The results show that contextual modulation occurs whether the orientation-defined figure appears in the left or right eye, but when the figure appears in both eyes, the response profile is virtually identical to that for the case where the figure appears in only one eye. These results suggest that extra-RF contextual modulation is a robust feature of V1 neural function, similar to the long-studied RF properties of cells in this area. The study concludes that extra-RF contextual modulation may reflect a sophisticated neural correlate of perception, rather than merely low-level image processing.This study investigates extra-receptive field (extra-RF) contextual modulation in area V1 of awake, behaving macaque monkeys. Extra-RF contextual modulation refers to the modulation of V1 neuron activity by stimuli outside the neuron's receptive field (RF). The study used texture displays to examine how contextual modulation is influenced by disparity, color, luminance, and orientation cues. The results show that contextual modulation has a spatial extent of approximately 8 to 10 degrees parafoveally and is correlated with perceptual experience of binocularly rivalrous texture displays and surface occlusion. The modulation occurs with a latency of 80-100 milliseconds after stimulus onset, potentially allowing feedback from extrastriate areas to underlie this effect. The study also examined the effects of various visual cues on extra-RF contextual modulation. The results show that contextual modulation is evoked by a wide range of cues, including binocular disparity, color, luminance, and orientation. The modulation is not limited to any particular cue, suggesting that it serves an integrative function across diverse cues. The spatial extent of extra-RF modulation was also studied, and it was found to decline with increasing disc diameter, vanishing at approximately 10 degrees diameter. The study also examined the effects of binocular rivalry on extra-RF contextual modulation. The results show that contextual modulation occurs whether the orientation-defined figure appears in the left or right eye, but when the figure appears in both eyes, the response profile is virtually identical to that for the case where the figure appears in only one eye. These results suggest that extra-RF contextual modulation is a robust feature of V1 neural function, similar to the long-studied RF properties of cells in this area. The study concludes that extra-RF contextual modulation may reflect a sophisticated neural correlate of perception, rather than merely low-level image processing.