Dynamics of Alpha Rhythm Peak Frequency during Falling Asleep.

Changes in the frequency characteristics of EEG alpha rhythm in during falling asleep were studied in three healthy individuals under conditions of long-term isolation (MARS-500 project). Falling asleep was preceded by enhanced alpha rhythm frequency. An inverse correlation between the duration of falling asleep and prevailing alpha rhythm frequency during active and relaxed wakefulness was revealed in the left hemisphere. These results demonstrate the principal possibility of predicting the duration of falling asleep by using alpha rhythm spectral analysis. It is assumed that the frequency of the alpha range spectral peak can be a marker of drowsiness and reflect the current need for sleep.