Dynamic Phase Synchrony in Cortical Networks Underlying Conscious Awareness of Flicker

Flickering light sources, such as fluorescent lamps, evoke neural oscillations in the occipital cortex aligning with the flicker frequency; however, this flicker often remains outside conscious awareness. This discrepancy suggests neural mechanisms gating flicker perception. While functional magnetic resonance imaging studies have indicated the involvement of large-scale frontal and parietal networks in conscious flicker perception, their low temporal resolution limits insights into the underlying dynamic interactions. Using electroencephalography and physically identical stimuli near the critical flicker-fusion frequency, we investigated the temporal dynamics of phase synchrony and power distribution. Flicker perception was characterized by an early increase in higher beta-band (19-28 Hz) synchrony, followed by an increase in gamma-band (29-48 Hz) synchrony between fronto-parietal and parieto-occipital regions at approximately 300 ms post-stimulus. This was accompanied by a global expansion of gamma-band power from occipital to fronto-parietal areas-effects not observed during fused perception. Conversely, alpha-band (8-14 Hz) synchrony between anterior and posterior regions showed a more pronounced reduction specifically during fusion. These findings suggest that frequency-specific coordination and global information sharing across large-scale networks may underlie conscious flicker perception. The emergence of broad gamma-band synchrony at around 300 ms may reflect the integration of local sensory signals into distributed cortical networks. Early beta-band synchrony may facilitate the initiation of this process through top-down modulation, whereas attenuated alpha-band synchrony during fusion may reflect insufficient engagement of these networks. Such dynamic interplay within distributed networks is suggested to be involved in shaping the temporal resolution of visual awareness.