The microstructural integrity of the corpus callosum and associated impulsivity in alcohol dependence: a tractography-based segmentation study using diffusion spectrum imaging.

Previous post-mortem and structural magnetic resonance imaging (MRI) studies in patients with alcohol dependence have demonstrated abnormalities of brain white matter. The present study investigated the microstructural integrity in the corpus callosum and the associations of this integrity with neurobehavioral assessments. Twenty-five male cases fulfilling the DSM-IV diagnosis of alcohol dependence and 15 male control subjects were scanned using a 3T MRI system. Callosal fiber tracts were reconstructed by diffusion spectrum imaging tractography and were subdivided into seven functionally distinct segments. The microstructural integrity was quantified in terms of generalized fractional anisotropy (GFA). Compared with normal subjects, men with alcohol dependence showed lower GFA values on all segments of the corpus callosum. The segment interconnecting the bilateral orbitofrontal cortices was the most affected. The score on the Barratt Impulsivity Scale showed an inverse relationship with GFA on the callosal fiber tracts connecting the bilateral orbitofrontal cortices. Furthermore, the duration of regular use was negatively associated with GFA on the callosal fiber tracts connecting the bilateral temporal and parietal cortices. Our findings suggest that a high self-rated impulsivity level was associated with low anisotropy in white matter of corpus callosum sectors extending to the orbitofrontal cortex.