An Asymmetrical Hypothesis for the NREM-REM Sleep Alternation-What Is the NREM-REM Cycle?

Since the discovery of rapid eye movement (REM) sleep (Aserinsky and Kleitman, 1953), sleep has been described as a succession of cycles of non-REM (NREM) and REM sleep episodes. The hypothesis of short-term REM sleep homeostasis, which is currently the basis of most credible theories on sleep regulation, is built upon a positive correlation between the duration of a REM sleep episode and the duration of the interval until the next REM sleep episode (inter-REM interval): the duration of REM sleep would therefore predict the duration of this interval. However, the high variability of inter-REM intervals, especially in polyphasic sleep, argues against a simple oscillator model.

Psychophysical evaluation of chemosensory functions 5 weeks after olfactory loss due to COVID-19: a prospective cohort study on 72 patients.

Purpose: To evaluate the evolution of chemosensation via extended psychophysical testing in patients who suffered from sudden chemosensory loss due to coronavirus disease 2019 (COVID-19). Additionally, this study sought to determine whether odor threshold testing provided additional information on olfactory loss due to COVID-19 compared to the more common odor identification testing.

Methods: Prospective cohort study of patients with sudden chemosensory loss since February 2020 and confirmed COVID-19 infection via RT-PCR or serology testing.

Relationships between REM and NREM in the NREM-REM sleep cycle: a review on competing concepts.

Sixty-five years after the discovery of rapid eye movement (REM) sleep, the reasons why we sleep and why we need two states of sleep are still largely unclear. Moreover, the functional relationship between the two types of sleep remains the matter of much conjecture. Several questions come to mind.

Sleep ultradian cycling: Statistical distribution and links with other sleep variables, depression, insomnia and sleepiness-A retrospective study on 2,312 polysomnograms.

The number of alternations between Non-Rapid Eye Movement (NREM) sleep and Rapid Eye Movement (REM) sleep in humans is usually considered to consist of 4-5 cycles of about 90 minutes duration per night. Previous studies by our group showed a normal distribution on 26 healthy human subjects. The present study retrospectively analyzes the polysomnograms of 2,312 unmedicated patients who were admitted for medical and/or psychiatric reasons in the Erasme University Hospital between 2003 and 2014.