Slow rhythmic oscillations of EEG slow-wave amplitudes and their relations to midbrain reticular discharge.

The amplitude of anterior neocortical EEG slow-waves (0.5-4 Hz) measured during quiet waking, drowsy (WS) and synchronized sleep (S) states showed slow rhythmic oscillations in WS and S similar to those previously reported in midbrain reticular neurons (periods of 8-12 s). Abrupt changes in slow rhythms of unit discharge was reflected by similar changes in the amplitude of EEG slow-waves. Analyses on grouped data from many WS leads to S transitions showed no common phase relation between oscillations of EEG slow-wave amplitudes prior to S onset, but showed signs of a common phase relationship after. These findings, together with a significantly lower EEG synchronization level just before S onset in grouped data, suggest that the beginning of S is phase-related to oscillations of slow-wave amplitudes in WS.