title: The P50 auditory evoked potential in violent and non-violent patients with schizophrenia.
abstract: BACKGROUND
  Emotionally driven violence is facilitated by increased arousal. It may be a consequence of an information-processing deficit and the cognitive attributions for the stimuli given by the subject. The aim of this study was to compare the P50 evoked potential responses of violent patients with schizophrenia with non-violent patients with schizophrenia and healthy controls.
  
  
  METHODS
  Patients were classified into violent and non-violent in accordance to the Overt Aggression Scale. P50 auditory evoked potentials of 32 unmedicated patients with schizophrenia (violent=14, non-violent=18) and 17 healthy controls were recorded during five runs of 30 click pairs.
  
  
  RESULTS
  Healthy controls exhibited a lower S2/S1 ratio when compared to violent (p<0.001) and non-violent (p=0.04) patients. Using a cutoff point of 0.50 for S2/S1 ratio to define abnormal gating a significant proportion of violent patients did not show P50 suppression (71.4%) in comparison to non-violent patients (38.9%) and healthy controls (23.5%) (p=0.02).
  
  
  CONCLUSIONS
  Violent behavior in patients with schizophrenia could be associated with a disturbed information sensory gating. Violence in patients with schizophrenia may be facilitated by an increased arousal which may in turn be the result of an information-processing deficit.
authors.affiliation: Subdirección de Investigaciones Clínicas, Instituto Nacional de Psiquiatría Ramón de Fuente, Mexico City, Mexico.
authors.forename: Ana
authors.initials: A
authors.lastname: Fresán
authors.forename: Rogelio
authors.initials: R
authors.lastname: Apiquian
authors.forename: María
authors.initials: M
authors.lastname: García-Anaya
authors.forename: Camilo
authors.initials: C
authors.lastname: de la Fuente-Sandoval
authors.forename: Humberto
authors.initials: H
authors.lastname: Nicolini
authors.forename: Ariel
authors.initials: A
authors.lastname: Graff-Guerrero
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000374:Aggression / Q000502:physiology; D001143:Arousal / Q000502:physiology*; D002540:Cerebral Cortex / Q000503:physiopathology; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D011569:Psychiatric Status Rating Scales; D011930:Reaction Time / Q000502:physiology; D012016:Reference Values; D012559:Schizophrenia / Q000175:diagnosis* / Q000503:physiopathology; D012565:Schizophrenic Psychology; D012815:Signal Processing, Computer-Assisted; D014754:Violence / Q000523:psychology*