Information processing speed mediates the relationship between white matter and general intelligence in schizophrenia.
Several authors have proposed that schizophrenia is the result of impaired connectivity between specific brain regions rather than differences in local brain activity. White matter abnormalities have been suggested as the anatomical substrate for this dysconnectivity hypothesis. Information processing speed may act as a key cognitive resource facilitating higher order cognition by allowing multiple cognitive processes to be simultaneously available. However, there is a lack of established associations between these variables in schizophrenia. We hypothesised that the relationship between white matter and general intelligence would be mediated by processing speed. White matter water diffusion parameters were studied using Tract-based Spatial Statistics and computed within 46 regions-of-interest (ROI). Principal component analysis was conducted on these white matter ROI for fractional anisotropy (FA) and mean diffusivity, and on neurocognitive subtests to extract general factors of white mater structure (gFA, gMD), general intelligence (g) and processing speed (gspeed). There was a positive correlation between g and gFA (r= 0.67, p =0.001) that was partially and significantly mediated by gspeed (56.22% CI: 0.10-0.62). These findings suggest a plausible model of structure-function relations in schizophrenia, whereby white matter structure may provide a neuroanatomical substrate for general intelligence, which is partly supported by speed of information processing.
Division of Psychiatry, University of Edinburgh, Edinburgh, UK. Electronic address: s1465655@sms.ed.ac.uk.
Clara
C
Alloza
Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK; Department of Psychology, University of Edinburgh, Edinburgh, UK; Scottish Imaging Network: A Platform for Scientific Excellence (SINAPSE) Collaboration, Edinburgh, UK.
Simon R
SR
Cox
Division of Psychiatry, University of Edinburgh, Edinburgh, UK.
Barbara
B
Duff
Scottish Imaging Network: A Platform for Scientific Excellence (SINAPSE) Collaboration, Edinburgh, UK; Clinical Research Imaging Centre, University of Edinburgh, Edinburgh, UK; Centre for Clinical Brain Sciences, Western General Hospital, University of Edinburgh, Edinburgh, UK.
Scott I
SI
Semple
Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK; Scottish Imaging Network: A Platform for Scientific Excellence (SINAPSE) Collaboration, Edinburgh, UK; Centre for Clinical Brain Sciences, Western General Hospital, University of Edinburgh, Edinburgh, UK.
Mark E
ME
Bastin
Division of Psychiatry, University of Edinburgh, Edinburgh, UK; Scottish Imaging Network: A Platform for Scientific Excellence (SINAPSE) Collaboration, Edinburgh, UK; Centre for Clinical Brain Sciences, Western General Hospital, University of Edinburgh, Edinburgh, UK.
Heather C
HC
Whalley
Division of Psychiatry, University of Edinburgh, Edinburgh, UK; Scottish Imaging Network: A Platform for Scientific Excellence (SINAPSE) Collaboration, Edinburgh, UK; Centre for Clinical Brain Sciences, Western General Hospital, University of Edinburgh, Edinburgh, UK.
Stephen M
SM
Lawrie
D000328:Adult; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D007360:Intelligence / Q000502:physiology*; D008297:Male; D008606:Mental Processes / Q000502:physiology*; D008875:Middle Aged; D012559:Schizophrenia / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology*; D066127:White Matter / Q000000981:diagnostic imaging / Q000473:pathology*; D055815:Young Adult
Diffusion tensor MRI; General intelligence; Information processing speed; Schizophrenia; White matter