REM-like Oscillatory Theta Activity Predicts a Reduction in the Recuperative Value of Natural Human Sleep

Here, using data from two independent studies, we examine whether all of sleep is restorative or paradoxically whether some sleep processes incur a sleep debt that impacts next-day wakefulness. Specifically, we examine whether rapid eye movement (REM) sleep is such a process due to its similarity to wake activity, which is causal for sleep debt. To investigate this, we first develop a novel measure of REM neural activity (REM-like oscillatory theta activity (OTA)), overcoming limitations of current sleep scoring. We find that naturally occurring average REM-like OTA across individuals: 1) is associated with increased neurobehavioral sleep debt; 2) explains 25-38% (p ≤ 0.001) of sleep debt differences across individuals the following day; 3) occurs throughout sleep to various degrees, contrary to current sleep scoring; and 4) can be measured automatically, without cumbersome manual scoring.