title: Sensory gating in schizophrenia: P50 and N100 gating in antipsychotic-free subjects at risk, first-episode, and chronic patients.
abstract: BACKGROUND
  Abnormal sensory gating in schizophrenia has frequently been reported; however, only limited data on unmedicated patients and patients at risk to develop a psychosis have, as yet, been available.
  
  
  METHODS
  P50 and N100 suppression were assessed with an auditory double-click paradigm in five groups: 18 at-risk subjects who did not develop a full psychosis within the follow-up period of 2 years, 21 truly prodromal subjects who developed frank psychosis within the follow-up period, 46 antipsychotic-naïve subjects with first-episode schizophrenia, 20 antipsychotic-free subjects with chronic schizophrenia, and 46 healthy control subjects.
  
  
  RESULTS
  P50 and N100 suppression indices differed significantly between groups and were lowest in chronic schizophrenia patients. Compared with healthy control subjects, P50 suppression was significantly impaired in at-risk subjects, truly prodromal and first-episode patients (stimulus 2 [S2]/stimulus 1 [S1] P50 amplitude ratio), and chronic schizophrenia patients (difference and ratio), and N100 suppression was significantly reduced in truly prodromal and first-episode patients (S1-S2 difference) and in chronic schizophrenia patients (difference and ratio) but not at-risk subjects. At-risk subjects with and without conversion to psychosis did not significantly differ on any test parameter.
  
  
  CONCLUSIONS
  Sensory gating is already impaired in early stages of schizophrenia, though this is most prominent in chronic stages. Future studies will have to clarify the type and impact of variables modifying sensory gating disturbances, such as illness progression and genetic load. Furthermore, the meaning and nature of differences between P50 and N100 suppression need further elucidation.
authors.affiliation: Department of Psychiatry and Psychotherapy, University of Cologne, Cologne, Germany. anke.brockhaus-dumke@uk-koeln.de
authors.forename: Anke
authors.initials: A
authors.lastname: Brockhaus-Dumke
authors.forename: Frauke
authors.initials: F
authors.lastname: Schultze-Lutter
authors.forename: Ralf
authors.initials: R
authors.lastname: Mueller
authors.forename: Indira
authors.initials: I
authors.lastname: Tendolkar
authors.forename: Andreas
authors.initials: A
authors.lastname: Bechdolf
authors.forename: Ralf
authors.initials: R
authors.lastname: Pukrop
authors.forename: Joachim
authors.initials: J
authors.lastname: Klosterkoetter
authors.forename: Stephan
authors.initials: S
authors.lastname: Ruhrmann
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D020233:Gait Disorders, Neurologic / Q000209:etiology*; D006801:Humans; D008297:Male; D009433:Neural Inhibition; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000150:complications*