NEUROPHYSIOLOGICAL AND NEUROPSYCHOLOGICAL EVIDENCE FOR ATTENTIONAL DYSFUNCTION IN SCHIZOPHRENIA

The behavior of the P50 wave of the auditory evoked potential in a pai red stimulus or conditioning-testing paradigm has been used as a measu re of sensory gating disturbance in schizophrenia. Schizophrenics fail to decrement the P50 response to the second stimulus of the pair, so that the ratio of the test to the conditioning amplitude is elevated o ver normal values. The aim of this study was to compare this neurophys iological measure to neuropsychological measures of attention and memo ry. As expected, schizophrenics performed worse than controls on most measures. The time to complete a digit cancellation test, a measure of sustained attention, was found to be particularly longer in schizophr enics than in control subjects. Furthermore, the increased time to com plete this task correlated with the increased ratio of the amplitude o f the test P50 response to the conditioning response in the schizophre nics. Thus, a neurophysiological defect in sensory gating may relate t o a disorder in sustained attention in schizophrenia. Although the P50 wave may come from the hippocampus, neuropsychological measures of ve rbal learning and memory were not correlated with alterations in the P 50 ratio.