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Dynamics of the human EEG during prolonged wakefulness: evidence for frequency-specific circadian and homeostatic
D Aeschbach1, J R Matthews, T T Postolache
1Clinical Psychobiology Branch, National Institute of Mental Health, Bethesda, MD 20892, USA. aschbach@box-a.nih.gov
Abstract:
The electroencephalogram (EEG) of nine healthy individuals was recorded at half-hourly intervals during approximately 40 h of sustained wakefulness in a constant routine protocol. EEG power density in the 0.75-9.0 Hz range exhibited a global increasing trend, and a local trough in the evening, centered approximately 6 h prior to the temperature minimum. The former could be attributed to a wake-dependent influence, and the latter to a circadian influence. Power density in the 9.25-12.0 Hz band showed a circadian modulation, the trough coinciding with the minimum of the endogenous rhythm of body temperature, whereas a wake-dependent influence was not evident. Power density in the 12.25-25.0 Hz range exhibited a wake-dependent increase, whereas a circadian modulation was absent. It is concluded that the circadian pacemaker and the wake-dependent (i.e. homeostatic) process affect the waking EEG in a frequency-specific manner.