Theta-band EEG functional connectivity during emotional music in disorders of consciousness: wPLI differences between MCS and UWS

Background With the increasing number of patients with disorders of consciousness (DOC), accurate diagnosis—particularly differentiation between the minimally conscious state (MCS) patients and the unresponsive wakefulness syndrome (UWS) patients—is critical for subsequent treatment planning. Objective To investigate differences in theta-band electroencephalography (EEG) functional connectivity between MCS and UWS patients during emotional music stimulation, and to explore their responsiveness to different emotional music conditions. Methods Forty-eight DOC patients were enrolled (MCS, n = 32; UWS, n = 16). EEG was recorded during the resting state and while listening to four emotion-specific music conditions (sad, fearful, happy, and peaceful). Theta-band functional connectivity was quantified across four scalp regions (frontal, parieto-occipital, temporal, and central), with weighted phase lag index (wPLI) as the primary metric and phase-locking value (PLV) and coherence (Coh) as supplementary measures. Between-group comparisons (MCS vs. UWS) and within-group comparisons (each music condition vs. resting state) were performed to evaluate group differences in theta-band connectivity and its responsiveness to emotional music. Results Between-group analyses showed that significant differences between MCS and UWS under rest and emotional music conditions were mainly located in frontal, parieto-occipital, and central regions ( p < 0.05), whereas no consistent significant differences were observed in the temporal region. Overall, theta-band wPLI was higher in the UWS group than in the MCS group. Within-group analyses further demonstrated that, in the MCS group, frontal theta-band wPLI increased significantly after listening to sad ( p = 0.019) and peaceful ( p = 0.016) music, while no significant within-group changes were observed in the UWS group. Conclusion In the context of emotional music stimulation, θ -band wPLI and its dynamic modulatory capacity may reflect differences in the reactivity of residual networks between MCS and UWS patients.