title: White matter organization and neurocognitive performance variability in schizophrenia.
abstract: BACKGROUND
  White matter alterations in schizophrenia are associated with deficits in neurocognitive performance. Recently, across task within-individual variability (WIV) has emerged as a useful construct for assessing the profile in cognitive performance in schizophrenia. However, the neural basis of WIV has not been studied in patients with schizophrenia.
  
  
  METHODS
  Twenty-five patients with schizophrenia (SZ) and 27 healthy comparison subjects (HC) performed a computerized neurocognitive battery (CNB) and underwent diffusion tensor imaging (DTI). WIV for performance accuracy and speed on the CNB was calculated across-tasks. Voxel-wise group comparisons of white matter fractional anisotropy (FA) were performed using tract-based spatial statistics (TBSS). The relationship between accuracy and speed WIV on the CNB and white matter FA was examined within the regions that differentiated patients and healthy comparison subjects.
  
  
  RESULTS
  SZ had higher WIV for performance accuracy and speed as compared to HC. FA in SZ compared to HC was reduced in bilateral frontal, temporal and occipital white matter including a large portion of the corpus callosum. In white matter regions that differed between patients and comparison subjects, higher FA in the left cingulum bundle and left fronto-occipital fasciculus were associated with lower CNB speed WIV for HC, but not SZ. Accuracy WIV was not associated with differences in white matter FA between SZ and HC.
  
  
  CONCLUSIONS
  We provide evidence that WIV is greater in patients with SZ and that this greater within-individual variability in performance in patients is associated with disruptions of WM integrity in specific brain regions.
authors.affiliation: Neuropsychiatry Section, Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, United States. roalf@upenn.edu
authors.forename: David R
authors.initials: DR
authors.lastname: Roalf
authors.forename: Kosha
authors.initials: K
authors.lastname: Ruparel
authors.forename: Ragini
authors.initials: R
authors.lastname: Verma
authors.forename: Mark A
authors.initials: MA
authors.lastname: Elliott
authors.forename: Raquel E
authors.initials: RE
authors.lastname: Gur
authors.forename: Ruben C
authors.initials: RC
authors.lastname: Gur
mesh_terms: D000328:Adult; D016880:Anisotropy; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping; D003072:Cognition Disorders / Q000209:etiology* / Q000473:pathology*; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000150:complications* / Q000473:pathology; D055815:Young Adult