EFFECTS OF CLOZAPINE ON AUDITORY EVENT-RELATED POTENTIALS IN SCHIZOPHRENIA

Background: Schizophrenia is associated with cognitive deficits that a re an intrinsic component of the disorder. Clozapine is an atypical an tipsychotic that is superior to typical agents in the treatment of pos itive symptoms. The degree to which clozapine ameliorates cognitive de ficits, however, is still controversial. Mismatch negativity (MMN), N2 00 (N2), and P300 (P3) are cognitive even-related potentials (ERPs) th at index preattentive (MMN) and attention-dependent information proces sing (N2, P3) and provide a measure of cognitive deficits associated w ith schizophrenia. In schizophrenic patients deficient generation of M MN, N2, and P3 has been observed suggesting impairments of discrete st ages of information processing. Methods: This study investigates the e ffects of clozapine treatment on MMN, N2, and P3 generation, Patients were recruited from a haloperidol-controlled double-blind treatment st udy of clozapine in chronic schizophrenia. ERPs were obtained at the b eginning of the study and after 9 weeks (4 patients) and 16 weeks (13 patients) of treatment. Results: Clozapine treatment was associated wi th a significant increase of P3 amplitude, which was not observed in t he haloperidol group; however, clozapine treatment did not affect defi cits in MMN and N2, Conclusions: These findings suggest that clozapine -in contrast to conventional antipsychotics-improves electrophysiologi cal measures of attention-dependent information processing, but does n ot ameliorate preattentive deficits. Biol Psychiatry 1998;44:716-725 ( C) 1998 Society of Biological Psychiatry.