Rosenblum Yevgenia, Jafarzadeh Esfahani Mahdad, Adelhöfer Nico, Zerr Paul, Furrer Melanie, Huber Reto, Roest Famke F, Steiger Axel, Zeising Marcel, Horváth Csenge G, Schneider Bence, Bódizs Róbert, Dresler Martin
Radboud University Medical Centre, Donders Institute for Brain, Cognition and Behavior, Nijmegen, Netherlands.
Child Development Center and Children's Research Center, University Children's Hospital Zürich, University of Zürich, Zürich, Switzerland.
Elife. 2025 Jan 9;13:RP96784. doi: 10.7554/eLife.96784.
Sleep cycles are defined as episodes of non-rapid eye movement (non-REM) sleep followed by an episode of REM sleep. Fractal or aperiodic neural activity is a well-established marker of arousal and sleep stages measured using electroencephalography. We introduce a new concept of 'fractal cycles' of sleep, defined as a time interval during which time series of fractal activity descend to their local minimum and ascend to the next local maximum. We assess correlations between fractal and classical (i.e. non-REM - REM) sleep cycle durations and study cycles with skipped REM sleep. The sample comprised 205 healthy adults, 21 children and adolescents and 111 patients with depression. We found that fractal and classical cycle durations (89±34 vs 90±25 min) correlated positively (=0.5, p<0.001). Children and adolescents had shorter fractal cycles than young adults (76±34 vs 94±32 min). The fractal cycle algorithm detected cycles with skipped REM sleep in 91-98% of cases. Medicated patients with depression showed longer fractal cycles compared to their unmedicated state (107±51 vs 92±38 min) and age-matched controls (104±49 vs 88±31 min). In conclusion, fractal cycles are an objective, quantifiable, continuous and biologically plausible way to display sleep neural activity and its cycles.
睡眠周期被定义为非快速眼动（non-REM）睡眠阶段接着快速眼动睡眠阶段的过程。分形或非周期性神经活动是通过脑电图测量的觉醒和睡眠阶段的一个公认标志。我们引入了一个新的睡眠“分形周期”概念，定义为分形活动时间序列下降到其局部最小值并上升到下一个局部最大值的时间间隔。我们评估分形睡眠周期和经典（即非快速眼动 - 快速眼动）睡眠周期持续时间之间的相关性，并研究快速眼动睡眠缺失的周期。样本包括205名健康成年人、21名儿童和青少年以及111名抑郁症患者。我们发现分形周期和经典周期持续时间（89±34分钟对90±25分钟）呈正相关（=0.5，p<0.001）。儿童和青少年的分形周期比年轻人短（76±34分钟对94±32分钟）。分形周期算法在91 - 98%的病例中检测到快速眼动睡眠缺失的周期。与未服药状态相比，服用药物的抑郁症患者表现出更长的分形周期（107±51分钟对92±38分钟），且比年龄匹配的对照组更长（104±49分钟对88±31分钟）。总之，分形周期是一种客观、可量化、连续且生物学上合理的方式来展示睡眠神经活动及其周期。
