Dynamic Phase Synchrony in Cortical Networks Underlying Conscious Awareness of Flicker.

Abstract

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.