[Spectral analytical study on the developmental properties of EEG in children: variability of EEG in normal and mentally retarded children (author's transl)].

The present study aimed at clarifying the characteristics of variability of the resting arousal EEGs in normal and mentally retarded children. Their ages ranged from 3 to 15 years in 58 normal and from 7 to 18 in 63 retarded. The EEG was recorded monopolarly from six regions of the scalp. The data analysed by a multipurpose digital computer comprised auto-power spectra and a coefficient of variation of power at each frequency. The variability of power at peak within the theta frequency band in both groups of children showed a notably higher value as compared with other frequency bands in all regions. We discussed some of the problems of treating this variability of power as a general characteristic of theta waves or as a developmental one.