Visual evoked potential characteristics and subtypes of schizophrenia.

Visual evoked potentials (VEPs) were recorded from the midoccipital area of 72 schizophrenic patients. The amplitude of wave VI (100- to 115-millisecond latency) was reduced after the addition test for 15 minutes. It recovered to the pretest level later, and four types of recovery curves were found; marked reduction in amplitude 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 1-Hz flashes which started 1 minute, 3 minutes, and 5 minutes after the end of the test). Each type closely corresponded to paranoid, atypical hebephrenic, typical hebephrenic, and simple schizophrenia, respectively.