[A visual evoked potential study of atypical endogenous psychoses]

Because of the continued controversies about the nature of atypical endogenous psychoses and their relationship to typical endogenous psychoses such as schizophrenias or affective disorders, a visual evoked potential (VEP) study was performed on 11 patients with atypical endogenous psychosis, 6 schizophrenics (both medicated) and 11 normal controls to observe the characteristics of cerebral responsiveness in atypical endogenous psychoses. VEPs were elicited by flashes. A modification of Kadobayashi's addition task method was employed as the mental task and the changes in P 100 amplitude of the VEPs at the time points of 1, 3, 5, 7, 9 and 11 minutes after the task were estimated from the amplitude ratios before and after the task. A majority of the patients with atypical endogenous psychosis (73%) showed remarkable increases in VEP amplitude after the mental task, and the rest showed decreases regardless of the variety in their clinical features such as confusion, elation or depression, being in part consistent with the findings in bipolar affective disorders previously reported by this author and his colleagues. On the other hand, the schizophrenics all showed remarkable decreases in VEP amplititude after the task with a mean value of amplitude ratios of 65.1 +/- 14.7. In group comparisons between both disorders of the amplitude ratio at each time point within 11 minutes after the task and in their average, the differences reached a statistically significant level at all time points except 11 minutes after the task and in their average. In the normal controls the amplitude changes were slight with a mean value of amplitude ratios of 95.1 +/- 9.9. Between the normal controls and the schizophrenics, significant differences were found at all time points except 5 and 11 minutes after the task and in their average. Patients with atypical endogenous psychosis showed higher incidences of the amplitude ratios deviating from the normal range than the normal controls. The differences were of statistical significance at all time points except 3 and 11 minutes after the task and except in their average. From the viewpoint of the neurophysiological aspect of cerebral evoked potentials the author discussed the similarities of brain excitability in atypical endogenous psychoses and affective disorders.