title: Global-local visual processing in schizophrenia: evidence for an early visual processing deficit.
abstract: BACKGROUND
  Abnormalities in early-stage visual processing might contribute to observed higher neurocognitive deficits in schizophrenia, but to date no clear link has been established. Schizophrenia has been associated with deficits in the magnocellular visual pathway, suggesting a relative bias for processing elemental (local) as opposed to configural (global) aspects of a hierarchical stimulus; however, global-local paradigm studies in schizophrenia have yielded mixed results.
  
  
  METHODS
  In the current study, global-local and event-related potential (ERP) procedures were concomitantly used to assess temporal and spatial characteristics of hierarchical visual stimulus processing abnormalities.
  
  
  RESULTS
  Patients (n = 24) had slower and less accurate responses to global stimuli than a healthy comparison group (n = 29). They exhibited a marked decrement in N150 ERP amplitude, which correlated with speed of response to global stimuli. They also failed to show an augmented P300 response to local stimuli.
  
  
  CONCLUSIONS
  Behavioral and physiological data are consistent and support a global visual processing deficit in schizophrenia. This is manifest at a relatively early stage of visual processing and might relate to physiological disturbances in areas V3/V3a of the extrastriate cortex.
authors.affiliation: Neuropsychiatry Section, Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Johnson
authors.forename: Natasha
authors.initials: N
authors.lastname: Lowery
authors.forename: Christian
authors.initials: C
authors.lastname: Kohler
authors.forename: Bruce I
authors.initials: BI
authors.lastname: Turetsky
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003627:Data Interpretation, Statistical; D004569:Electroencephalography; D018913:Event-Related Potentials, P300; D005071:Evoked Potentials / Q000502:physiology; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D012565:Schizophrenic Psychology; D014796:Visual Perception / Q000502:physiology*