title: Event-related gamma activity in schizophrenia patients during a visual backward-masking task.
abstract: OBJECTIVE
  Schizophrenia patients experience deficits in many aspects of cognition and perception. Abnormalities in gamma activity may underlie some of these deficits, including rapid processing of visual stimuli. This study examined event-related gamma range activity during a visual backward-masking task in schizophrenia patients and normal comparison subjects.
  
  
  METHODS
  Event-related gamma activity was recorded in 15 normal comparison subjects and 32 schizophrenia patients. Participants had event-related gamma activity recorded while viewing 60 unmasked visual targets and 240 trials of visual backward masking. Effects of group, accuracy (correct versus incorrect), stimulus-onset asynchrony, and regional activity (left versus right hemisphere, anterior versus posterior regions) were assessed.
  
  
  RESULTS
  Schizophrenia patients had significantly reduced gamma activity in relation to comparison subjects during the backward-masking task. Normal comparison subjects showed significantly greater gamma activity in the right hemisphere, whereas schizophrenia patients did not show this pattern of lateralization. For the unmasked target, there was no group effect and no significant interactions in gamma-band responses.
  
  
  CONCLUSIONS
  These results extend previous findings of abnormal gamma range activity in schizophrenia patients. Patients showed overall less gamma activity and failed to show lateralization of activity to the right hemisphere during masking, but they showed comparable levels of gamma activity to unmasked stimuli. Schizophrenia patients' poorer performance during a masking task may be partly influenced by this abnormal level and the distribution of gamma activity.
authors.affiliation: Department of Psychology, UCLA, Los Angeles, CA, USA. jkwynn@ucla.edu
authors.forename: Jonathan K
authors.initials: JK
authors.lastname: Wynn
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Light
authors.forename: Bruno
authors.initials: B
authors.lastname: Breitmeyer
authors.forename: Keith H
authors.initials: KH
authors.lastname: Nuechterlein
authors.forename: Michael F
authors.initials: MF
authors.lastname: Green
mesh_terms: D000328:Adult; D001931:Brain Mapping; D003072:Cognition Disorders / Q000175:diagnosis / Q000503:physiopathology; D004569:Electroencephalography / Q000706:statistics & numerical data*; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010470:Perceptual Masking / Q000502:physiology; D010775:Photic Stimulation; D011569:Psychiatric Status Rating Scales; D011597:Psychomotor Performance / Q000502:physiology; D012559:Schizophrenia / Q000175:diagnosis* / Q000503:physiopathology; D012565:Schizophrenic Psychology; D014796:Visual Perception / Q000502:physiology