title: Evaluation of magnocellular pathway abnormalities in schizophrenia: a frequency doubling technology study and clinical implications.
abstract: BACKGROUND
  Visual processing deficits have been reported for patients with schizophrenia. Previous studies demonstrated differences in early-stage processing of schizophrenics, although the nature, extent, and localization of the disturbance are unknown. The magnocellular and parvocellular visual pathways are associated with transient and sustained channels, but their respective contributions to schizophrenia-related visual deficits remains controversial.
  
  
  OBJECTIVE
  The aim of this study was to evaluate magnocellular dysfunction in schizophrenia using frequency doubling technology.
  
  
  METHODS
  Thirty-one patients with schizophrenia and 34 healthy volunteers were examined. Frequency doubling technology testing was performed in one session, consisting of a 15-minute screening strategy followed by the C-20 program for frequency doubling technology.
  
  
  RESULTS
  Schizophrenic patients showed lower global mean sensitivity (30,97 ± 2,25 dB) compared with controls (32,17 ± 3,08 dB), p<0.009. Although there was no difference in the delta sensitivity of hemispheres, there was a difference in sensitivity analysis of the fibers crossing the optic chiasm, with lower mean sensitivity in the patient group (28,80 dB) versus controls (30,66 dB). The difference was higher in fibers that do not cross the optic chiasm, with lower mean sensitivity in patients (27,61 dB) versus controls (30,26 dB), p<0.005.
  
  
  CONCLUSIONS
  Our results suggest that there are differences between global sensitivity and fiber sensitivity measured by frequency doubling technology. The different sensitivity of fibers that do not cross the optic chiasm is consistent with most current etiological hypotheses for schizophrenia. The decreased sensitivity responses in the optic radiations may significantly contribute to research assessing early-stage visual processing deficits for patients with schizophrenia.
authors.affiliation: Laboratório Interdisciplinar de Neuroimagem e Cognição, Departamento de Psiquiatria, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Fabiana Benites Vaz de
authors.initials: FB
authors.lastname: Lima
authors.forename: Carolina Pelegrini Barbosa
authors.initials: CP
authors.lastname: Gracitelli
authors.forename: Augusto
authors.initials: A
authors.lastname: Paranhos Junior
authors.forename: Rodrigo Affonseca
authors.initials: RA
authors.lastname: Bressan
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D015350:Contrast Sensitivity / Q000502:physiology; D005260:Female; D005829:Geniculate Bodies / Q000503:physiopathology*; D006801:Humans; D008297:Male; D012559:Schizophrenia / Q000150:complications / Q000503:physiopathology*; D058609:Visual Field Tests / Q000379:methods*; D014795:Visual Pathways / Q000503:physiopathology*; D014796:Visual Perception / Q000502:physiology*