Changes in visual evoked potentials of schizophrenics after addition test.

Visual evoked potentials were obtained for schizophrenics, neurotics and patients with affective disorders, and comparison between those before and after an addition test for 15 min was made. Reduction in amplitude and prolongation of latency of the potential were observed in schizophrenics after the test, while there was no change after that in neurotics and patients with affective psychosis. In schizophrenics, 4 types of changes in amplitude of the potential could be seen after the test. Namely, marked reduction occurred in A1 (A1 type), in A3 with fast recovery (A3f type), in A3 with slow recovery (A3s type), and in A5 (A5 type). (A1, A3, A5: Averaged potentials evoked by 1c/sec flashes which started 1 min, 3 min and 5 min after the end of the test.) Each type closely corresponded to paranoid schizophrenia, atypical hebephrenia, typical hebephrenia and simple schizophrenia, respectively.