SPATIAL PATTERNS IN THE BACKGROUND EEG UNDERLYING MENTAL DISEASE IN MAN

The spatial patterns underlying differences in the background EEGs of schizophrenic, manic and depressed patients and a group of normal cont rols has been examined during the eyes open and eyes closed resting co nditions and during 3 cognitive tasks. The method of principal-compone nt analysis was used to extract spatial patterns which are common to t he EEGs of 2 groups but which account for maximally different proporti ons of the combined variances. The common spatial patterns in all poss ible pairings of the groups were used to extract variance-related feat ure vectors from the individual EEG epochs in the 2 groups and the mea ns of these vectors were subjected to statistical analyses. The result s of these analyses indicate that there are significant differences in the EEGs from all 4 of the groups. The spatial patterns underlying th e features which are significantly different in each comparison are sh own graphically and used to suggest which brain regions might be impli cated in each of the psychiatric conditions and how these are affected by the cognitive condition. The main results are that the EEGs in the schizophrenic group can be characterized by left-sided hyperactivity, in the depressed group by right-sided hyperactivity and in the manic group by bilateral hyperactivity and that these characteristics are be st elicited by different cognitive states.