Abstract
It has been proposed that in order for a stimulus to reach consciousness, visual information that is relayed to higher brain areas must also be fed back to the early visual areas for a reverberatory strengthening of the representation. This theory further proposes that when these feedback signals from higher brain areas encounter new activity elicited by a different stimulus, this reactivation, and thus the conscious perception of the original target, is inhibited. The present study measured the neural correlates of conscious perception in a backwards metacontrast masking paradigm, in which the detection of a target is inhibited by a subsequent mask. After a fixation cue in the current experiment, target and mask pairs were presented at a constant SOA such that participants detected roughly half of the targets. Using the event related optical signal (EROS), a brain imaging technique with high spatial and temporal resolution, we examined not only the differential activity elicited by detected and undetected targets, but also preparatory activity prior to the target onset that might predict subsequent target detection. Preliminary analyses revealed a parietal area more active before detected targets, preceding an observed reduction in parietal alpha power measured with simultaneous EEG recording. Furthermore, the largest difference in activity in primary visual areas between detected and undetected targets occurred relativity late (+ 150 ms), after the initial feed forward processing, consistent with the dependence of visual awareness on re-entrant reverberations.