Late positive component amplitude in schizophrenics and alcoholics in two different paradigms

Abstinent alcoholics, unmedicated schizophrenics, and controls were tested in two paradigms designed to elicit the late positive component. Experiment A used frequent stimuli of differing incentive value and Experiment B used infrequent stimuli of differing perceptual discriminability. Alcoholics and schizophrenics showed late positive components that were significantly reduced in amplitude compared to controls. The patient groups were similar in their late component amplitudes. Control subjects showed a substantially wider response range than the patient groups. The narrow response range in both patient groups was manifested in diminished late component amplitudes to both stimuli in both experiments. The intraclass correlation coefficient of late component amplitudes for both patient groups was significantly greater than that of the controls.