Factor analysis of EEG in healthy and diseased subjects

Factor analysis was applied to EEG recordings of healthy and diseased subjects to be analyzed by an "on line" broad-band frequency analyser. Differences between the healthy and the diseased as to the number of given factors were established by means of the Lawly test. Up to 6 factors were determined for patients, up to 3 for the healthy. On medication, the number of factors rose in the delta and beta bands, remaining unchanged in the alpha band dropping the theta band. The patients manifested a sort of interindividual uniformity and intraindividual simplification. Except for different sites of pathological foci, the patients' EEG recordings were more like each other than those of healthy subjects. The latter might have undergone a similar process on medication. This enabled to establish more factors in the patients, moreover in such a way as to expose some general laws of cortical electric activity, such as unified cortical activity despite its various facets, hemispheral specificity, and finally also a relative autonomy of the frontal lobes.