Is the primary visual cortex modulated by visual awareness?
The role of V1 in visual awareness and attention has been a matter of intense debate due to its unique position in the visual hierarchy, the entrance stage of visual processing in cortex. Using a two-by-two factorial functional magnetic resonance imaging design with binocular suppression, we found that the visibility or invisibility of a visual target led to only non-significant BOLD effects in the human primary visual cortex, while directing attention toward and away from the target had much larger and robust effects across all subjects. The difference in the lower level limit of BOLD activation between attention and awareness illustrates dissociated neural correlates of the two processes. Our results agree with previously reported V1 BOLD effects on attention while they invite a reconsideration of the functional role of V1 in visual awareness.