[Developmental characteristics of the alpha waves of EEG in normal healthy children]

The records of waking state electroencephalography (EEG) of 1,340 normal children aged from 3 to 12 years were subjected to analysis using an autoregressive model. The results were summarized as follows. (1) 6,814 components of second-order activities were obtained through component analysis of the 1,218 EEG records. The frequency polygons of damping frequency of the second-order component waves verified several modes, each of which was enhanced in the eight frequency ranges. (2) The average percent-power of the alpha-1 waves decreased with increasing ages from 3 years, whereas that of the alpha-2 waves increased. That of the alpha-3 waves showed no change with ages. (3) The average damping times of alpha-2 waves increased with increasing ages. (4) Dominancy in frequency showed a course of two step increments at 3-6 and 10 years of age. The former was chiefly due to the increase in the alpha-1 wave and the latter in the alpha-2 wave. There were no significant increases of alpha-3 waves. (5) By means of EEG pattern discrimination, the differences in alpha components among different age groups were obtained as generalized (Maharanobis') distances. The alpha-1 activity showed a significant difference in amount between the age group of 3-6 years and the other age groups. The alpha-2 activity showed a significant difference in amount between the age group of 10 years and the other age groups. (6) The development of brain activity proceeds faster in the posterior areas and relatively slower in the central areas.