M9 Sleep architecture and circadian rhythms

Title

Sleep regulation is classically described by Borbely's two-process model: Process S, a homeostatic pressure that rises during wakefulness and declines during sleep, and Process C, a central circadian oscillator generated by the suprachiasmatic nucleus (SCN), formalized here as a direct extension of the Kuramoto phase oscillator model introduced in E09, synchronized by the ambient light signal. Sleep propensity results from the combination of both processes, and the circadian clock also modulates the secretion of melatonin, suppressed by exposure to light. The progression through the different stages of sleep (wake, NREM, REM) can be described as a Markov chain of transitions between states, while slow wave activity during deep sleep directly reflects the dissipation of accumulated homeostatic pressure. The misalignment between the internal circadian clock and the required environmental schedule (jet lag, shift work) is quantified as the phase difference between the two.

ID:4281