title: P300 alterations in schizophrenic patients experiencing auditory hallucinations.
abstract: BACKGROUND
  Attentional deficits have been implicated in the pathophysiology of auditory hallucinations in schizophrenia. Since the latency of the P300 component of event-related potentials (ERPs) is considered to be a sensitive measure of stimulus classification speed, while its amplitude-a measure of attentional resource allocation when memory updating is engaged, the present study focuses on the comparison of P300 between healthy subjects and schizophrenic patients experiencing auditory hallucinations and treated with clozapine and olanzapine.
  
  
  METHODS
  The auditory P300 was assessed during the anticipatory period of a short memory test, in 16 male hallucinated schizophrenic patients and 13 male normal subjects matched for age and educational level. The patients were reexamined under identical conditions when their hallucinations had resolved following treatment with clozapine (8 patients) and olanzapine (8 patients).
  
  
  RESULTS
  The patients with hallucinations exhibited significantly reduced P300 amplitude at leads Fp1, F3, (C3-T5)/2, F4, Cz and Fz, when compared to the normal controls and at leads Fp1, F3, F4, (C4-T6)/2, C4, P4, Cz and Fz when compared to themselves during the remission phase. However logistic regression models revealed that the most important leads, differentiating the patient group before treatment either with the healthy controls, or with itself after treatment, were that at the left temporoparietal and at the left prefrontal area. Memory performance of the patient group, even after treatment and in spite of its significant improvement, remained significantly less than that of healthy controls. both antipsychotic agents had similar effects on the p300 amplitude and memory performance.
  
  
  CONCLUSIONS
  These findings indicate that auditory hallucinations in schizophrenia manifest abnormal aspects of attention, mediated by a distributed network involving or affecting the left temporoparietal and left prefrontal area. Additionally, the present study points to an improvement of attentional function in schizophrenic patients experiencing auditory hallucinations, both in the clozapine group but also in the olanzapine group.
authors.affiliation: Psychophysiology Laboratory, Department of Psychiatry, Eginition Hospital, University of Athens, 74 Vas. Sophias Ave., Athens, 11528, Greece. panchris@otenet.gr
authors.forename: Charalabos
authors.initials: C
authors.lastname: Papageorgiou
authors.forename: Panayiotis
authors.initials: P
authors.lastname: Oulis
authors.forename: Christos
authors.initials: C
authors.lastname: Vasios
authors.forename: Evagelos
authors.initials: E
authors.lastname: Kontopantelis
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Uzunoglu
authors.forename: Andreas
authors.initials: A
authors.lastname: Rabavilas
authors.forename: George N
authors.initials: GN
authors.lastname: Christodoulou
mesh_terms: D000328:Adult; D014150:Antipsychotic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001288:Attention / Q000187:drug effects* / Q000502:physiology; D001569:Benzodiazepines / Q000494:pharmacology / Q000627:therapeutic use; D016022:Case-Control Studies; D003024:Clozapine / Q000494:pharmacology / Q000627:therapeutic use; D018913:Event-Related Potentials, P300 / Q000187:drug effects* / Q000502:physiology; D006212:Hallucinations / Q000188:drug therapy / Q000209:etiology*; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D009483:Neuropsychological Tests; D000077152:Olanzapine; D011569:Psychiatric Status Rating Scales; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D012559:Schizophrenia / Q000150:complications* / Q000188:drug therapy
chemical_list: D014150:Antipsychotic Agents; D001569:Benzodiazepines; D003024:Clozapine; D000077152:Olanzapine