Although we have the impression that visual information flows continuously from our sensory channels, recent studies indicate that this is likely not the case. Rather, we sample visual stimuli rhythmically, oscillating at 5-10 Hz. Electroencephalography (EEG) studies have demonstrated that this rhythmicity is reflected by the phase of ongoing brain oscillations in the same frequency. Theoretically, brain oscillations could underlie the rhythmic nature of perception by providing transient time windows for information exchange, but this question has not yet been systematically addressed. We recorded simultaneous EEG-fMRI while human participants performed a contour integration task and show that ongoing brain oscillations prior to stimulus onset predict functional connectivity between higher and lower level visual processing regions. Specifically, our results demonstrate that the phase of a 7 Hz oscillation prior to stimulus onset predicts perceptual performance and the bidirectional information flow between the left lateral occipital cortex and right intraparietal sulcus, as indicated by psychophysiological interaction and dynamic causal modeling. These findings suggest that human brain oscillations periodically gate visual perception at around 7 Hz by providing transient time windows for long-distance cortical information transfer. Such gating might be a general mechanism underlying the rhythmic nature of human perception.
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