Comparison of the visually evoked response in drug-free chronic schizophrenic patients and normal controls.

Thirteen cooperative male drug-free chronic schizophrenic patients, and 11 mentally normal male controls were studied. The VER was recorded from scalp leads O1, O2, Oz, C3 and C4 to combined ear reference (A1--A2). The stimulus was an unpatterned flash of single intensity. Compared to normal controls, there were no consistent differences in wave peak latencies or amplitudes for chronic schizophrenics in any brain area tested. When the chronic schizophrenic patients were separated on the basis of high and low tryptophan uptake, using the Frohman--Gottlieb criteria, the high uptake group exhibited normal VERs while in the occipital regions the low tryptophan uptake group exhibited prolonged latencies and an increased amplitude for wave V when compared to normals. From BPRS scores the high tryptophan subgroup indicated a greater degree of psychopathology than the low tryptophan subgroup. The results obtained do not support an indole hallucinogen hypothesis for process schizophrenia.