Effects of risperidone on auditory information processing in neuroleptic-naive patients with schizophrenia spectrum disorders.

Early effects of risperidone (2.5 +/- 1 mg/day) on auditory information processing were investigated in 9 neuroleptic naive patients with schizophrenia spectrum disorders and 9 healthy controls by using event-related potentials (ERPs). ERPs were elicited during active auditory "oddball" paradigm and were recorded before and after two weeks of treatment. Baseline P3 latencies were significantly delayed in patient group. Risperidone treatment did not change P3 amplitudes and latencies. However, P2 amplitudes were reduced in parallel with the clinical improvement measured by Positive and Negative Syndrome Scale (PANSS). Although risperidone did not change neural bases of active attention after two weeks of treatment, the reduction of P2 amplitude suggests that risperidone may affect auditory information processing in patients with schizophrenia spectrum disorders who never have been exposed to antipsychotic treatment.