Previous investigations from our laboratory have suggested a possible interhemispheric difference in brain functioning in relation to the severity of a depressive psychopathological process. The present study has been carried out to extend the previous fìndings to comprise a more detailed symptom analysis of the depressive syndrome, several EEG characteristics, and a new method of EEG analysis. 22 depressed patients, most of them previously untreated, participated in the study. The patients were rated by means of a highly reliable rating scale for depression, and an EEG record was obtained from each of them. Analysis of possible relationships among clinical symptoms and EEG characteristics from different parts of the brain showed a complex pattern, quite different for each symptom. First when a systemic structural analysis of the EEG was performed by means of a special computer program, differential EEG syndromes could be identifìed. Patients with a high level of anxiety-depression showed a more pronounced functional involvement of the left precentral region than less severely ill patients.

In previous articles, evidence has been presented which supports the hypothesis that detectable neurophysiological changes occur in the course of affective disorders, mainly of a depressive type. The scope of the present report has been to expand the previous investigation to comprise variables not hitherto taken into account and to present a new approach to the analysis of EEG in psychiatry. This new approach, a systemic structural analysis, follows the concepts borrowed from the general system theory, and is based on the assumption that brain activity can be regarded as a type of hierarchical system. Hints about the theoretical principles beyond a systemic structural analysis of EEG are given, and the point is stressed that possible correlations between, e.g., neurophysiological and clinical variables must be sought starting from characteristics which are at a comparable level of integration in both realms. The preliminary findings of an international collaborative study of depressive syndromes are presented. 45 patients suffering from depressive syndromes of different aetiology and of varying severity participated in the study. These patients were rated by means of a rating scale which permitted a division for further analysis into subgroups according to the main symptomatology. The results show that characteristic neurofunctional structures can be identified which correspond to various symptomatological patterns. The occurrence of pronounced interhemispheric differences in electrical activity, related to the severity of the depressive syndrome, has also found further support in the results of this present investigation.