title: Perceptual organization and visual search processes during target detection task performance in schizophrenia, as revealed by fMRI.
abstract: BACKGROUND
  Past studies of perceptual organization in schizophrenia have demonstrated impairments binding fragmented stimulus components into unified representations. ERP and fMRI data indicate that even under conditions of adequate behavioral task performance, significant and meaningful changes in cortical and subcortical activation are present. Here, we examined, using fMRI, activation differences on a visual task wherein feature grouping was a precursor to the formation of distinct groups in the service of target location and identification.
  
  
  METHODS
  Fourteen schizophrenia patients and 16 healthy controls completed a target detection task with 2 conditions: one in which target-distractor grouping facilitates detection (the Isolated condition) and one in which it hinders detection (the Embedded condition). Stimuli were blocked by condition. Accuracy and RT data were obtained in addition to fMRI data.
  
  
  RESULTS
  Patients and controls did not differ significantly in accuracy or RT in either condition. Within this context, controls demonstrated greater recruitment of brain regions involved in visual-spatial processing, and the groups differed in activity in areas known to support visual search, visual analysis, decision making and response generation.
  
  
  CONCLUSIONS
  These findings are consistent with past data indicating reduced processing of stimulus organization, and the subsequent use of inefficient visual search strategies, even under conditions when behavioral performance is at a high level and matches that of healthy controls.
authors.affiliation: Department of Psychiatry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, University Behavioral HealthCare, Piscataway, NJ 08854, USA. silvers1@umdnj.edu
authors.forename: Steven M
authors.initials: SM
authors.lastname: Silverstein
authors.forename: Sarah
authors.initials: S
authors.lastname: Berten
authors.forename: Brian
authors.initials: B
authors.lastname: Essex
authors.forename: Sherrie D
authors.initials: SD
authors.lastname: All
authors.forename: Ravi
authors.initials: R
authors.lastname: Kasi
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Little
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply* / Q000473:pathology; D001931:Brain Mapping; D004192:Discrimination, Psychological / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood; D010468:Perceptual Disorders / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology; D010775:Photic Stimulation; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000150:complications / Q000473:pathology; D012565:Schizophrenic Psychology; D013223:Statistics as Topic; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen