Frontal white matter alterations are associated with executive cognitive function in euthymic bipolar patients

Background: Bipolar affective disorder (BD) is often associated with cognitive dysfunction in executive domains. However the biological underpinnings of cognitive deficits in BD are not sufficiently understood. A growing body of evidence indicates a loss of microstrucLural integrity in various white matter (WM) fiber tracts in BD. The aim of the current study was to assess potential links between WM structural abnormalities and cognitive performance in euthyrnic middle-aged BD patients (n=30) and matched healthy controls (n=32). Methods: Diffusion tensor imaging (DTI) data was carried out with both voxelwise (tract based spatial statistics, TBSS) and region-of-interest (ROI) based analysis. We compared multiple indices of diffusion including fractional anisotropy (FA), radial (DR), axial (DA) and mean diffusivities (MD). Results: Increased mean diffusivity was found in the fornix, anterior thalamic radiation, splenium and the truncus of the corpus callosum in BD patients compared with controls. These diffusion changes were significantly associated with poorer performance in executive tasks in BD patients. Conclusions: Our results indicate a direct link between executive cognitive functioning and abnormal WM microstructural integrity of fronto-limbic tracts in remitted BD patients, and add evidence to the neuronal disruption that underlies the residual symptomatology of BD. (C) 2013 Elsevier B.V. All rights reserved