[Information processing deficits in depression in terms of event-related potentials: in comparison with...

Information processing deficits characteristic of remitted major depression, which may be a vulnerability marker for the disease, were examined from two aspects by means of visual event-related potentials (ERPs) obtained during simple and discriminative response tasks: 1. To clarify the difference in cognitive dysfunction between both depressives and schizophrenics in remission, we compared the ERPs in remitted depressive patients (n = 11) and remitted schizophrenic patients (n = 9) with those of age, and sex-matched controls (n = 10). 2. To clarify the influence of aging on information processing in remitted depression, ERPs in young remitted depressives (20-46 years old, n = 11) were compared with those in older remitted depressives (52-75 years old, n = 11) in contrast to young (n = 10) and older (n = 11) controls. The remitted schizophrenics showed a retardation in NA and N2 latencies and a reduction in P3 amplitude. However, P1 increased in amplitude exclusively in the remitted depressives. The effect of stimulus discrimination on N1 seen in the controls was absent in both patient groups. The results suggest that the remitted depressives had an attentional deficit in early information processing reflected on P1 and N1 potentials, while the remitted schizophrenics had an extensive cognitive dysfunction reflected on N1, NA, N2, and P3 potentials. Although the effect of stimulus discrimination on N1 was absent in both young and older remitted depressive patients, older patients showed no effects of normal aging on ERPs such as P1 increase or N1 increase during discrimination tasks. Significant interaction effects between diagnosis and aging were found by ANOVA only in the laterality of the P1 amplitude. Older remitted depressives showed an unbalanced right-predominance in P1 amplitude. These results suggest that older remitted depressives had the same early information-processing deficit seen in the young remitted depressives as well as an overactivation over the right hemisphere in the attentional mechanism, irrespective of normal aging.