Effects of olanzapine on auditory P300 and mismatch negativity (MMN) in schizophrenia spectrum disorders

We investigated effects of olanzapine (5-10 mg/day) on passive and active attention in I I patients with schizophrenia spectrum disorders and 15 healthy controls by using auditory evoked potentials (AEPs) mismatch negativity (MMN) and P300. AEPs were elicited during active and passive auditory oddball paradigms before, after 2 weeks and 4 weeks of olanzapine treatment. Baseline P300 amplitudes, but not MMN, were significantly reduced in patients compared with controls. Although clinical signs improved significantly measured by Positive and Negative Syndrome Scale (PANSS), olanzapine had no significant effects on latencies and amplitudes of MMN and P300. Thus, olanzapine does not have effects on active and passive attention in patients with schizophrenia spectrum disorders. Four weeks olanzapine treatment may be insufficient for the improvement of cognitive dysfunction in terms of inability to focus on relevant stimuli in these patients. (c) 2005 Elsevier Inc. All rights reserved.