Dual homeostatic and circadian resonance shapes REM episode duration
TL;DR
The predicted high-instability extension and asymmetric REM profile provide a physiological estimate of accumulated sleep deficit as additional recovery time required to return toward the sleep–wake equilibrium setpoint.
Abstract
Abstract Rapid eye movement (REM) sleep is influenced by homeostatic and circadian processes, but why distinct REM episode-duration profiles—bell-shaped, flattened, amplified, near-linear, and bimodal—occur remains unresolved. The wave model of sleep dynamics treats REM sleep as a coherent sleep–wake mixed state stabilized by resonance between sleep and wake probability waves near their homeostatic equilibrium region. Here we extend this framework by adding a circadian REM-promoting resonance anchored to biological time. REM duration was modeled as a compound resonance generated by two fixed curve shapes: a broad homeostatic resonance and a narrower Lorentzian circadian resonance. Only amplitude, reflecting prior-wake-dependent state instability, and relative phase alignment were varied. This constrained model reproduced REM-duration profiles during regular sleep, chronic sleep extension, and post-deprivation recovery. Baseline and recovery sleep followed a conserved empirical compound resonance curve, indicating preservation of the equilibrium/resonance peak after acute sleep loss. The predicted high-instability extension and asymmetric REM profile provide a physiological estimate of accumulated sleep deficit as additional recovery time required to return toward the sleep–wake equilibrium setpoint. Independent validation came from a 525-night longitudinal extended-sleep dataset, in which reduced resonance overlap predicted mid-sleep wake clustering and sleep-continuity instability. These findings identify REM episode duration as a quantitative marker of homeostatic–circadian alignment, recovery need, and setpoint regulation.