Luminance is the most fundamental visual information. In comparison with other visual attributes, we know less about the neural mechanism responsible for coding luminance due to that visual neurons weakly respond to uniform luminance and many of them do not respond. Responses of a portion of neurons to luminance in the primary visual cortex are slower than those to contrast, which is thought to subserve the perceptual brightness induced by contrast at the borders of uniform luminance. However, our recent st...