Abstract
Sleep-wake driven changes in non-rapid-eye-movement sleep (NREM) sleep (NREMS) EEG delta (delta-)power are widely used as proxy for a sleep homeostatic process. Here, we noted frequency increases in delta-waves in sleep-deprived mice, prompting us to re-evaluate how slow-wave characteristics relate to prior sleep-wake history. We identified two classes of delta-waves; one responding to sleep deprivation with high initial power and fast, discontinuous decay during recovery sleep (delta2) and another unrelated to time-spent-awake with slow, linear decay (delta1). Reanalysis of previously published datasets demonstrates that delta-band heterogeneity after sleep deprivation is also present in human subjects. Similar to sleep deprivation, silencing of centromedial thalamus neurons boosted subsequent delta2-waves, specifically. delta2-dynamics paralleled that of temperature, muscle tone, heart rate, and neuronal ON-/OFF-state lengths, all reverting to characteristic NREMS levels within the first recovery hour. Thus, prolonged waking seems to necessitate a physiological recalibration before typical NREMS can be reinstated.
Hubbard, Jeffrey