1041 Increased Delta-Gamma Coupling During Phasic REM Sleep in Isolated RBD

Abstract Introduction This study examines the phasic and tonic states of REM sleep with a focus on idiopathic rapid eye movement sleep behavior disorder (iRBD), which is characterized by REM sleep without atonia and is thought to be a precursor to alpha-synucleinopathies. By examining specific EEG dynamics associated with dreaming, specifically delta and gamma power during phasic REM sleep states and their correlation with iRBD characteristics, we aim to develop a comprehensive understanding of dream enactment. Methods In-depth analysis was performed using polysomnography (PSG) and 21-channel EEG data from 13 iRBD patients and 10 controls who had been drug-free for six months and had not progressed to alpha-synucleinopathy. REM sleep states were categorized into phasic and tonic states based on eye movements, and the Kullback-Leibler modulation index was used to assess phase-amplitude coupling (PAC) and calculated phase-locked amplitudes (PLA) to determine interphase coupling. Gini coefficients were calculated to identify within- and between-component imbalances, and extensive statistical analysis was performed using permutation cluster analysis, repeated measures analysis of variance, Mann-Whitney U tests, and correlation assessments to identify differences and relationships. Results The results showed a significant increase in delta-gamma coupling during phasic REM sleep in RBD compared to controls (FDR p 0.0001). A detailed comparison of the delta signal component, the component in which the imbalance was found (FDR p 0.0001), at different spatial locations revealed distinct patterns of delta-gamma coupling, with significant phase-amplitude coupling (PAC) observed in frontal and parietal cortex. These results showed a clear linear relationship (FDR p 0.0001), with notable correlations with the RBDQ-KR (FDR p 0.0001) and the REM atonia index (FDR p=0.0003). The average area under the ROC-AUC curve for separating the RBD group from the control group based on PAC values was 0.88. Conclusion The study significantly highlights the role of EEG metrics, especially the coupling of delta and gamma oscillation during REM sleep, as key indicators of dream-related enactment in iRBD. The strong correlations with clinical indices not only underscore the diagnostic value of these EEG measures but also suggest their potential to revolutionize the diagnosis and understanding of iRBD. Support (if any)