Z-transformed EEG power spectra of children with Down syndrome vs a control group.

Standardized EEG records of eighty-eight children with Down syndrome aged between six months and five years were analysed. The EEGs were digitalized, evaluated by spectral analysis, and subjected to z-transformation, a method which allows a direct comparison of the Down syndrome children with a normal control group (Munich Developmental Longitudinal Study). The results show a significant increase in absolute power, especially theta power; the absolute alpha power is less markedly increased or even decreased. The most significant differences, however, are observed when calculating the relative alpha power. Children with Down syndrome show a reduced relative alpha power already at the age of six months, and this reduction becomes even more prominent with growing age.