The electroencephalogram in the middle-aged and the elderly.

A survey was made of the electroencephalographic (EEG) changes during the human lifespan. It was found that the EEG changes during childhood and adolescent maturation continue even between the ages of 30 and 60 years. There is a decrease in the abundance of alpha activity, with a reduction in the fast part and a relative increase in the slow part of the alpha band. In the span of life between 60 and 90, there is an increase of slow waves with a progressive slowing during the aging process and a shift in the dominant frequency from 9 cps to 7 cps. Computerization of results in the beta band (above 13 cps) enables differentiation of the waves of the lower part (13-25 cps) from those of the upper part (above 25-30 cps). The lower part of the beta band decreases parallel to the alpha activity but the upper part of the beta band increases in amount during the aging process. The meaning of the divergent behavior of these sub-groups of beta activity in the aged is discussed. The EEG seems to be an important factor in the study of aged persons.