Several studies have demonstrated that visual perception cycles as a function of the alpha phase but only a few reports have demonstrated that multiple rhythms modulate behavior on a fine-grained temporal scale ( 5, 16вЂ“ 19). Importantly, endogenous entrainment does not require rhythmicity in the input stream but reflects an intrinsic mechanism to enable predictions ( 15). In particular, endogenous low-frequency entrainment is thought to reflect a substrate of top-down processing ( 11вЂ“ 14). It has been suggested that slow-frequency activity in the delta range (<5 Hz) might reflect a mechanism for endogenous attentional selection and predictions ( 9, 10). However, it is currently unclear which cortical regions and mechanisms mediate the directed top-down control of alpha oscillations ( 2). The gating-by-inhibition hypothesis postulates that alpha serves as a mechanism to route information to task-relevant cortical sites ( 8) but might also be under top-down control ( 6, 7). Numerous studies have shown that visual perception critically depends on prestimulus alpha-band (8вЂ“12 Hz) activity ( 3вЂ“ 7). However, it is currently unclear how contextual information is dynamically integrated to support visual perception. It has been suggested that rhythmic brain activity constitutes a key mechanism to coordinate information flow in the human cerebral cortex by transiently forming task-relevant large-scale networks ( 1). Visual perception is flexible, selective, and rapidly integrates sensory evidence with endogenous high-level expectations and predictions ( 1, 2). Taken together, this study presents converging behavioral and electrophysiological evidence for frontal delta-mediated top-down control of posterior alpha activity, selectively facilitating visual perception. Simultaneous source-reconstructed EEG and cross-frequency directionality analyses revealed that this delta activity originated from prefrontal areas and modulated posterior alpha power. Importantly, delta-mediated top-down control diminished the behavioral effects of bottom-up alpha entrainment. We identified a 2- to 4-Hz delta signature that modulated posterior alpha activity and behavior during predictive trials. The rapid stream was presented either rhythmically at 10 Hz, to entrain parietooccipital alpha oscillations, or arrhythmically. We tested whether a predictive context that was embedded in a rapid visual stream modulated the perception of a subsequent near-threshold target. Here, we probed visual perception on a fine-grained temporal scale to study the oscillatory dynamics supporting prefrontal-dependent sensory processing. It has been suggested that different frequency bands index distinct canonical computations. Conscious visual perception is proposed to arise from the selective synchronization of functionally specialized but widely distributed cortical areas.

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