title: Multivariate pattern analysis of functional magnetic resonance imaging data reveals deficits in distributed representations in schizophrenia.
abstract: BACKGROUND
  Multivariate pattern analysis is an alternative method of analyzing functional magnetic resonance imaging (fMRI) data, which is capable of decoding distributed neural representations. We applied this method to test the hypothesis of the impairment in distributed representations in schizophrenia. We also compared the results of this method with traditional general linear model (GLM)-based univariate analysis.
  
  
  METHODS
  Nineteen schizophrenia and 15 control subjects viewed two runs of stimuli-exemplars of faces, scenes, objects, and scrambled images. To verify engagement with stimuli, subjects completed a 1-back matching task. A multivoxel pattern classifier was trained to identify category-specific activity patterns on one run of fMRI data. Classification testing was conducted on the remaining run. Correlation of voxelwise activity across runs evaluated variance over time in activity patterns.
  
  
  RESULTS
  Patients performed the task less accurately. This group difference was reflected in the pattern analysis results with diminished classification accuracy in patients compared with control subjects, 59% and 72%, respectively. In contrast, there was no group difference in GLM-based univariate measures. In both groups, classification accuracy was significantly correlated with behavioral measures. Both groups showed highly significant correlation between interrun correlations and classification accuracy.
  
  
  CONCLUSIONS
  Distributed representations of visual objects are impaired in schizophrenia. This impairment is correlated with diminished task performance, suggesting that decreased integrity of cortical activity patterns is reflected in impaired behavior. Comparisons with univariate results suggest greater sensitivity of pattern analysis in detecting group differences in neural activity and reduced likelihood of nonspecific factors driving these results.
authors.affiliation: Department of Psychiatry and Imaging Research Center, University of California Davis, Sacramento, California 95817, USA. jhyyoon@ucdavis.edu
authors.forename: Jong H
authors.initials: JH
authors.lastname: Yoon
authors.forename: Diana
authors.initials: D
authors.lastname: Tamir
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Minzenberg
authors.forename: J Daniel
authors.initials: JD
authors.lastname: Ragland
authors.forename: Stefan
authors.initials: S
authors.lastname: Ursu
authors.forename: Cameron S
authors.initials: CS
authors.lastname: Carter
mesh_terms: D000328:Adult; D001931:Brain Mapping; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015999:Multivariate Analysis; D009483:Neuropsychological Tests; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D017397:Prefrontal Cortex / Q000098:blood supply / Q000503:physiopathology; D012559:Schizophrenia / Q000473:pathology* / Q000503:physiopathology*; D055815:Young Adult