Fractal cycles of sleep: a new aperiodic activity-based definition of sleep cycles

• DOI: 10.7554/elife.96784.1
• Publication Date: 2024-05-21T13:26:07Z
• Authors: Yevgenia Rosenblum; Mahdad Jafarzadeh...; Nico Adelhöfer; Paul Zerr; Melanie Furrer; Reto Huber; Axel Steiger; Marcel Zeising; Csenge G. Horváth; Bence Schneider; Róbert Bódizs; Martin Dresler
• Keywords: Aperiodic graph; Sleep

Nocturnal human sleep consists of 4 – 6 ninety-minute cycles defined as episodes non-rapid eye movement (non-REM) followed by an episode REM sleep. While are considered fundamental components sleep, their functional significance largely remains unclear. One the reasons for a lack research progress in this field is absence “data-driven” definition cycles. Here, we proposed to base such on fractal (aperiodic) neural activity, well-established marker arousal and stages.We explored temporal dynamics activity during nocturnal using electroencephalography 205 healthy adults aged 18 75 years. Based observed pattern fluctuations, introduced new concept, “fractal” cycle time interval which descends from its local maximum minimum then leads back next maximum. Then, assessed correlations between “classical” (i.e., non-REM REM) durations. We also studied with skipped i.e., where phase replaced “lightening” Finally, validated concept children adolescents (range: 8 17 years, n = 21), group characterized deeper higher frequency well major depressive disorder (n 111), condition altered structure (in addition clinical symptoms).We found that durations (89 ± 34 min vs. 90 25 min) correlated positively (r 0.5, p < 0.001). Cycle-to-cycle overnight showed inverted U-shape both classical gradual decrease absolute amplitudes descents ascents early late cycles.In adults, duration participant’s age negatively -0.2, 0.006). Children had shorter compared young (76 94 32 min, The algorithm detected 53/55 (96%) cases.Medicated patients depression longer own unmedicated state (107 51 92 38 0.001) age-matched controls (104 49 88 31 0.001).In conclusion, objective, quantifiable, continuous biologically plausible way display cycling nature. They useful healthy, pediatric populations should be extensively advance theoretical structure.