Electrophysiological correlates of visual consciousness and selective attention.

It is not clear whether attention is necessary or not for consciousness. We studied the relationship between attention and consciousness by tracking their electrophysiological correlates. The participants attended to visual targets, ignored nontargets in the prespecified visual field and ignored all stimuli in the opposite field. Visual consciousness was varied by masking. Our results showed that the earliest electrophysiological correlate of consciousness emerged independent of the manipulations of spatial and nonspatial attention. Conversely, the electrophysiological correlate of attention, selection negativity, was elicited regardless of the presence or absence of consciousness. Only the correlates of later, higher-level conscious processes strongly depended on attention. Thus, the electrophysiological brain responses reflecting visual consciousness and attention are initially independent of each other.