Processing speed impairment in schizophrenia is mediated by white matter integrity

H. Karbasforoushan, B. Duffy, J. U. Blackford, N. D. Woodward

Research output: Contribution to journalArticlepeer-review

44 Scopus citations

Abstract

Background. Processing speed predicts functional outcome and is a potential endophenotype for schizophrenia. Establishing the neural basis of processing speed impairment may inform the treatment and etiology of schizophrenia. Neuroimaging investigations in healthy subjects have linked processing speed to brain anatomical connectivity. However, the relationship between processing speed impairment and white matter (WM) integrity in schizophrenia is unclear. Method. Individuals with schizophrenia and healthy subjects underwent diffusion tensor imaging (DTI) and completed a brief neuropsychological assessment that included measures of processing speed, verbal learning, working memory and executive functioning. Group differences in WM integrity, inferred from fractional anisotropy (FA), were examined throughout the brain and the hypothesis that processing speed impairment in schizophrenia is mediated by diminished WM integrity was tested. Results. WM integrity of the corpus callosum, cingulum, superior and inferior frontal gyri, and precuneus was reduced in schizophrenia. Average FA in these regions mediated group differences in processing speed but not in other cognitive domains. Diminished WM integrity in schizophrenia was accounted for, in large part, by individual differences in processing speed. Conclusions. Cognitive impairment in schizophrenia was mediated by reduced WM integrity. This relationship was strongest for processing speed because deficits in working memory, verbal learning and executive functioning were not mediated by WM integrity. Larger sample sizes may be required to detect more subtle mediation effects in these domains. Interventions that preserve WM integrity or ameliorate WM disruption may enhance processing speed and functional outcome in schizophrenia.

Original languageEnglish (US)
Pages (from-to)109-120
Number of pages12
JournalPsychological medicine
Volume45
Issue number1
DOIs
StatePublished - Jan 12 2015
Externally publishedYes

Keywords

  • Mediation
  • processing speed
  • schizophrenia
  • white matter

ASJC Scopus subject areas

  • Applied Psychology
  • Psychiatry and Mental health

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