The EEG preferential frequency as an indicator of the degree of wakefulness

Ever since electroencephalographic research began, interest has been focused on problems of the physiology, pathology, and symptomatology of the relationship between sleep and wakefulness. Following preliminaries, the present paper describes a combined procedure for the determination of the EEG preferential frequency, and by random sampling statistically examines its suitability for indicating the fluctuations of activation level as a control measure. A trained volunteer gradually increased his degree of wakefulness, reliably producing parallel changes in the preferential frequency in three frequency bands. A standardised manual period analysis as control produced largely the same results. The preferential frequency has considerable value for indicating the degree of wakefulness.