Ontogenic development of EEG-asymmetry in early infantile autism

Autoregressive (AR) analysis and component analysis were done on EEGs during sleep stage 2 in normal and autistic children, since AR-coefficients of EEG characterize the autocovariance and power spectral density of EEG. In addition, as the generalized distance of the average AR-coefficient vector of an EEG group at one side from that at the opposite side exhibits an F-distribution, the statistical inferences were determined, as to whether there is hemispheric specialization in EEG in 21 right-handed autistic children and whether there is a difference between the AR-spectral pattern of EEG in the autistic children and that of 28 normal children of the same age range. The results obtained are as follows: 1. Significant hemispheric lateralization in EEG at the significant level of 0.01 was observed in normal children, whereas no lateralization was confirmed in autistic children. 2. Random click stimulation had cumulative effects on the hemispheric lateralization in the normal children, but not in the autistic children. On the contrary, the effects of random flash light stimulation on hemispheric asymmetry were verified in the autistic children as well as in the normal children. 3. The EEG components of autistic children were significantly different from the normal ones in the frequency range of alpha-2 component waves at bilateral frontal (Fp1 and Fp2) regions and the activity of these component waves was higher in the autistic children than in the normal ones over 5 years old. 4. These findings suggest that autistic children are not only less responsive to external stimuli, but also neurophysiologically less active in the internal regulatory mechanism.