Abstract
It was proposed to analyse electroencephalograms (eeg) and to express them quantitatively with three statistical measures, mean amplitude _??_, mean period _??_ and persistence P. The persistence is the mean of the number of waves greater than _??_/2 following successively without inter-ruption.
1. 50-250 eeg were taken at each subject and analysed. The histogram of P had its- maximum at the value of P 4-8, and the mean values of P were 9.5, 8, 24, 7.65, 7.1 and 4.98 in the standard passive state of consciousness of normal subjects.
2. The theoretical meaning of persistence was discussed. The value of P 5.6 was calculated from the theory for the ideal eeg in which all waves are independent of one another and belong to one and the same population of waves.
3. In general, the persistence is greater than 5.6, and this relation was regarded as expression of dependence among individual waves.
4. The persistence is smaller than 5.6 in cerebral excitation and under other conditions that more than a single sort of waves appear in eeg. It was theoretically proven that the persistence can decrease below the ideal value 5.6 by mixing more than one sort of waves.
5. Mixing of β-waves with normal α-waves reduces both P and _??_, whereas mixing of δ-waves with normal α-waves decreases P, but in-creases _??_.
