title: Dysfunction of early-stage visual processing in schizophrenia.
abstract: OBJECTIVE
  Schizophrenia is associated with deficits in higher-order processing of visual information. This study evaluated the integrity of early visual processing in order to evaluate the overall pattern of visual dysfunction in schizophrenia.
  
  
  METHODS
  Steady-state visual-evoked potential responses were recorded over the occipital cortex in patients with schizophrenia and in age- and sex-matched comparison volunteers. Visual-evoked potentials were obtained for stimuli composed of isolated squares that were modulated sinusoidally in luminance contrast, number of squares, or chromatic contrast in order to emphasize magnocellular or parvocellular visual pathway activity.
  
  
  RESULTS
  Responses of patients to magnocellular-biased stimuli were significantly lower than those of comparison volunteers. These lower response levels were observed in conditions using both low luminance contrast and large squares that biased processing toward the magnocellular pathway. In contrast, responses to stimuli that biased processing toward the parvocellular pathway were not significantly different between schizophrenia patients and comparison volunteers. A significant interaction of group and stimulus type was observed in the condition using low luminance contrast.
  
  
  CONCLUSIONS
  These findings suggest a dysfunction of lower-level visual pathways, which was more prominent for magnocellular than parvocellular biased stimuli. The magnocellular pathway helps in orienting toward salient stimuli. A magnocellular pathway deficit could contribute to higher-level visual cognitive deficits in schizophrenia.
authors: Department of Veterans Affairs New York Harbor Health Care System, New York, New York, USA. butler@nki.rfmh.org
authors: P D
authors: PD
authors: Butler
authors: I
authors: I
authors: Schechter
authors: V
authors: V
authors: Zemon
authors: S G
authors: SG
authors: Schwartz
authors: V C
authors: VC
authors: Greenstein
authors: J
authors: J
authors: Gordon
authors: C E
authors: CE
authors: Schroeder
authors: D C
authors: DC
authors: Javitt
mesh_terms: D003072:Cognition Disorders / Q000175:diagnosis / Q000503:physiopathology; D015350:Contrast Sensitivity / Q000502:physiology; D005074:Evoked Potentials, Visual / Q000502:physiology; D005556:Form Perception / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009778:Occipital Lobe / Q000503:physiopathology*; D010775:Photic Stimulation; D012559:Schizophrenia / Q000175:diagnosis* / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D014793:Visual Cortex / Q000503:physiopathology; D014795:Visual Pathways / Q000503:physiopathology*; D014796:Visual Perception / Q000502:physiology*