As to the study by Vyazovskiy et al., this is a really elegant demonstration
that full-blown, slow-wave sleep, as indicated by highly synchronized “global”
EEG slow-wave activity and associated neuronal off and on states, develops
from awake periods. They show that, in awake periods, slow-wave activity and associated neuronal on and off periods can also occur, but in waking, these events occur locally in restricted neuron circuits and are not synchronized across wider cortical networks. In fact, with increasing time spent awake, and increasing sleep propensity, such local off states increase in frequency and also occur more often in synchrony with off states in other cortical areas.
These findings very much support the concept originally proposed by Alexander Borbely from the University of Zurich, Switzerland, of a homeostatic sleep regulation that even holds at the level of local cortical neuron populations. It suggests that cortical networks and associated functions that are more or less intensively used during waking develop a kind of “neuronal fatigue” that requires...