To survive in a complex world, it is important that unattended, but salient, input can still draw one's attention. In this article, we suggest that posterior alpha oscillations (8-13Hz) provide a mechanism for prioritizing and ordering unattended visual input according to 'relevance'. Gamma oscillations (30-100Hz) that are phase-locked to the alpha oscillations keep competing unattended representations apart in time, thus creating a sequence of perceptual cycles. As inhibition gradually lowers within an alpha cycle, the ordered sequence of competing input is activated, producing a temporal phase code for saliency. The proposed mechanism is based on recent experiments indicating that the phase of alpha activity modulates perception and that alpha oscillations are produced by periodic pulses of inhibition.
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