Electrophysiological evidence for reduced latent inhibition in schizophrenic patients

The present study examined latent inhibition (LI) effects in 17 acute and 1 6 partially remitted schizophrenic patients, and in 20 healthy controls, by measuring manual response latencies and event-related potentials (ERPs) du ring an association learning task. ERPs were recorded to elucidate the role of attention in the LI effect. Subjects performed a go/no-go task with an auditory conditional stimulus predicting a visual go command. Half of the s ubjects in each diagnostic group were pre-exposed to the conditional stimul us which had been used as an irrelevant distracter in a preceding discrimin ation task. Independent of diagnostic group membership, pre-exposed subject s showed slower manual responses to go stimuli than non-pre-exposed subject s, reflecting a robust LI effect. The N100 wave after the conditional stimu li, however, showed a differential pattern: pre-exposure increased N100 amp litudes in acute schizophrenics, whereas pre-exposed control subjects showe d a trend for decreased N100. The amplitude of the contingent negative vari ation (CNV) was unaffected by pre-exposure. The ERP results suggest that ac ute schizophrenics have a deficit in learned inattention to irrelevant stim uli. However, the intact LI effect in schizophrenics at the motor speed lev el shows that human LI is a complex phenomenon depending on the tasks and m easures used. (C) 2000 Elsevier Science B.V. All rights reserved.