Familiarity synchronizes brain rhythms during natural viewing

Our perception of the world is shaped not only by sensory information, but also by prior experience. However, how familiarity alters the coordination of neural representations across distributed brain networks remains unclear. Rhythmic neural activity provides a potential mechanism for coordinating information across sensory and higher-order brain regions in the light of previous experience. Here, we thus investigated whether familiarity alters the coordination of brain rhythms during naturalistic viewing. Participants who were either familiar or unfamiliar with the television series Game of Thrones viewed clips from the series while EEG or fMRI was recorded. We calculated the intersubject correlations of neural activity across EEG frequency bands and related this rhythmic activity to fMRI BOLD responses. Across participants, all brain rhythms showed reliable intersubject synchrony and related to activity across large-scale brain networks. Familiarity selectively enhanced intersubject synchronisation in beta and gamma rhythms, with these effects reflected in visual and default mode brain regions. Moreover, beta and gamma band activity were modulated by similar aspects of the movie, suggesting coordinated familiarity-related processing. These findings show that familiarity selectively shapes rhythmic neural dynamics across the cortex, providing a mechanism through which prior experience alters the coordination of neural representations during naturalistic perception.