Synchronization between Cortical and Muscular Systems is Modulated by Audiovisual Emotional Stimulation

Emotions result from complex, dynamic interactions between the brain and the body. While the neural basis of emotional processing is well established, increasing evidence highlights the importance of its coordinated activity with peripheral systems, such as facial or shoulder muscles, in shaping and reflecting emotional experiences. This study investigated cortico-muscular synchronization as a mechanism of brain-body communication during emotionally evocative stimuli. EEG and EMG signals from 32 participants in the DEAP dataset were analyzed as they viewed music videos designed to elicit different valence-arousal combinations. Directional interactions between cortical rhythms and the zygomaticus major (zEMG) and trapezius (tEMG) muscles were quantified using a network-based framework combining controlled time-delay stability (cTDS) and partial cross-correlation. Emotion-related modulation was observed in both EEG-EMG networks but was stronger and more widespread in EEG-tEMG networks, with significant differences in bottom-up θ, β, and γ influences and localized top-down effects (p < 0.05). Most significant differences between emotion states involved the tEMG→ γ link at occipital and temporal sites (p = 0.008 and p = 0.007, respectively), and tEMG→ θ links at central sites (p = 0.003). EEG-zEMG connectivity showed comparable link strengths to those of EEG-tEMG but only minor emotion-dependent changes, with three significant effects (p < 0.05): γ →zEMG at C4 and bottom-up zEMG → θ and zEMG → α at C3. These findings suggest that affective modulation selectively reorganizes cortico-muscular networks, with more pronounced effects in postural muscles compared to expressive muscles. This agrees with neuropsychological findings of noticeable muscle tension in the trapezius muscle when stressed.