Neural Oscillations Track Subjective and Pupillary Arousal During Naturalistic Movie Viewing.

Movies evoke dynamic emotional experiences that fluctuate moment-to-moment. While fMRI has mapped these fluctuations, the real-time continuous oscillatory dynamics underlying naturalistic viewing remain less understood. In this study, 25 adults watched an emotionally rich short film while EEG, continuous subjective arousal annotations and pupil diameter were recorded. Inter-subject correlation (ISC) analyses revealed robust synchronization in behavioural and pupillary arousal across the cohort. Leveraging these shared, group-level arousal trajectories to probe individual-level cortical processing, we mapped the neural networks correlating with these two arousal signals. Both pupillary and subjective arousal negatively correlated with low-frequency power in occipitoparietal regions, reflecting bottom-up sensory gain control and attentional gating. Furthermore, high-arousal epochs were marked by low-frequency desynchronization in the precuneus; this cortical activation likely indexes the rapid retrieval of episodic memories required to update the viewer's situational model during plot shifts. Finally, while both measures tracked low-frequency acoustic features in the auditory cortex, subjective arousal was more prominently associated with extended top-down semantic networks and central theta activity. These findings highlight that while pupillary arousal heavily reflects bottom-up sensory intensity, subjective reporting captures active cognitive integration. Together, this demonstrates how emotional arousal acts as a dynamic control signal, orchestrating a complex interplay of sensory gating, memory updating and top-down evaluation to make sense of the unfolding narrative.