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Previous studies [7,8] have addressed the question of the extent to which EEG characteristics typical of adult schizophrenia patients apply to children with early childhood autism (ECA). It has become possible to state the problem in these terms since clinical studies of ECA demonstrated that positive symptoms could arise and that ECA could develop into a processual disorder of the schizophrenia type [1]. Many children with ECA are diagnosed with "schizophrenia" at age 7-8 years. We were interested to determine whether EEG data could be used to obtain early information regarding the probability of this change in diagnosis. Published views on this question are contradictory, while solution of the problem is very important for the timely provision of corrective and rehabilitation services. Definition of the possible criteria for the development of ECA into schizophrenia based on EEG data are of great scientific and social significance. Despite the specific features of cognitive impairments in ECA associated with the characteristics of information processing [19] and interhemisphere interactions [25], similarities in the mechanisms of these two types of pathology can be suggested [22]. Studies have shown [7,8] that cognitive loading in healthy children produces increases in the spectral power and coherence of fast rhythms from baseline levels. In early childhood autism, the spectral power of the alpha rhythm decreases, while the spectral power of the gamma rhythm is higher than normal, including in baseline conditions. Cognitive loading of patients produces smaller changes in the spectral power of fast rhythms than seen in normal subjects. Decreased alpha-rhythm power is seen in children with autism and in adults with schizophrenia, with both positive and negative symptoms [13]. Similar changes have also been described in adolescents with schizophrenia spectrum disorders [3]. The increased spectral power of the We present here a comparative analysis of spectral power and mean coherence of the theta and gamma rhythms in healthy boys and boys with early childhood autism aged 5-7 years (mean age 6 years 1 month) in the state of rest and on cognitive loading (counting). In contrast to the situation in patients, the background theta rhythm in healthy children showed a marked fronto-occipital gradient. In early childhood autism, the spectral power of the theta rhythm in baseline conditions had lower values than in healthy children, while baseline gamma rhythm power was greater. In healthy children, cognitive loading led to decreases in spectral power and mean coherence in the theta rhythm and increases in these measures of the gamma rhythm. In patients with early childhood autism, cognitive loading produced no marked changes from baseline in either rhythm. In healthy children, counting shifted the focus of theta-rhythm activity to the right occipital area, which did not occur in patients with early childhood autism.

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