Twenty-one schizophrenics and 21 controls were exposed to a tenminute sequence of frequent and infrequent auditory stimuli. The amplitude of the third positive-going component (p3) of the average evoked response to infrequent stimuli was much larger in the control group (P<.0003). Using a P3 amplitude of 3.20μv in the first 2.5 minutes as a dividing point, only seven of the 42 subjects were misclassified. This amplitude had a significant correlation of -.48 with patient's age at first hospitalization. Amplitude of the second positive-going component (P2) to frequent stimuli was also much larger in the control group (P<.003). This amplitude has a significant correlation of -.41 with medication dosage in terms of equivalent amounts of chlorpromazine. Behavioral scales failed to correlate significantly with evoked response measures. Evoked response latencies did not distinguish the two groups.
Roth WT, Cannon EH. Some Features of the Auditory Evoked Response in Schizophrenics. Arch Gen Psychiatry. 1972;27(4):466-471. doi:10.1001/archpsyc.1972.01750280034007