Resting-State EEG Characteristics of Tardive Dyskinesia: Spectral and Network Connectivity Insights.

Background and Hypothesis: Tardive dyskinesia (TD) is an often irreversible movement disorder, mostly resulting from exposure to dopamine receptor antagonists. The electrophysiological characteristics of TD remain poorly understood. Resting-state electroencephalography (EEG) may help characterize frequency-specific cortical oscillatory and network alterations related to TD. We hypothesized that TD-related neurophysiological alterations may be reflected in cortical spectral power, hemispheric asymmetry, and large-scale functional connectivity. Study Design: Resting-state EEG was recorded with a 32-channel system in 67 participants: 20 patients with TD, 25 patients without TD, and 22 healthy controls. Analyses focused on spectral power, hemispheric asymmetry, and functional connectivity measured using phase-lag index. Electrode-level spectral power analyses were corrected using the false discovery rate, and network-level connectivity differences were assessed using network-based statistics. Subgroup clinical association analyses within the TD group were considered exploratory. Study Results: Compared with healthy controls, both TD and Non-TD patients showed increased theta relative power at central electrodes, including C4 and Cz, with group effects surviving false discovery rate correction. Cluster-based topographic analyses showed increased gamma2-gamma3 power over frontoparietal regions in TD patients and increased broadband gamma power over frontal-central regions in Non-TD patients relative to healthy controls. Within the TD subgroup, exploratory analyses showed nominal associations between hemispheric asymmetry indices and rapid medication withdrawal or duration of motor disorder, although these associations did not survive false discovery rate correction. Functional connectivity analyses identified frequency-specific network alterations, including reduced phase-locking value in the theta frequency band and reduced phase-lag index connectivity across alpha1, beta, and gamma frequency bands in TD-related comparisons. Conclusion: TD patients showed altered resting-state cortical oscillations and frequency-specific connectivity changes involving central, frontoparietal, and temporo-occipital networks. These findings provide preliminary electrophysiological evidence for cortical network involvement in TD and may inform future mechanistic studies. Given the modest sample size and exploratory nature of subgroup analyses, the findings should be interpreted cautiously and validated in larger longitudinal cohorts.