睡眠中の脳心リズムを用いた聴覚刺激タイミングの最適化：連続位相解析と多次元位相ロック
Sepehr Sardooeinasab1, Massimiliano de Zambotti2, Fiona C Baker2
1Department of Electrical Engineering, École de Technologie Supérieure, Notre-Dame St W, H3C 1K3 Montreal, QC, Canada.
Study Objectives:
Auditory stimulation during non-rapid eye movement (NREM) sleep effectively enhances slow oscillations (SOs) and slow-wave activity (SWA) when precisely timed to certain phases of the SO. However, timing precision remains a core challenge. Recent evidence suggests that heart rate (HR) components may provide effective complementary timing cues. This study examined which HR phases are associated with stronger stimulation responses using continuous phase analysis and evaluated a multidimensional phase-comparison approach that integrates HR and EEG SO phases.
Methods:
Polysomnography (PSG) recordings from 133 adolescents were analyzed. Auditory tones were delivered randomly every 15-30 seconds during NREM sleep. Instantaneous phases of EEG SO (~0.8 Hz) and HR components in the low-frequency (LF; 0.04-0.15 Hz) and high-frequency (HF; 0.15-0.4 Hz) bands were extracted for continuous phase analysis. Tone-evoked SO amplitude and SWA were further compared across three phase-locking strategies: unimodal (SO-only or HR-component-only) and combined (EEG-HR).
Results:
Responses were largest when tones occurred near the HR-LF up-peak and HR-HF down-peak. Phase analyses showed that tones occurring at the optimal HR component phases were accompanied by increases in SO amplitude by up to ~22 μV and SWA by 12%, indicating that peripheral signals can serve as strong, independent timing cues. SO-only phase-locking also produced notable effects (~18 μV SO amplitude, 19% SWA increase). Combining SO and HR phases yielded the greatest effects, with increases of ~38 μV in SO amplitude and 32% in SWA.
Conclusions:
Oscillatory phases derived from heart rhythms provide effective timing information that may be useful for closed-loop auditory stimulation and reflect brain-heart coupling during sleep. A multidimensional phase-based approach that integrates EEG slow oscillations with instantaneous heart rate phases may support more precise control and stronger enhancement of deep sleep than unimodal approaches, suggesting a new framework for closed- loop neuromodulation.
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