Cognitive control and white matter callosal microstructure in methamphetamine-dependent subjects: a diffusion tensor imaging study.

BACKGROUND Methamphetamine (MA) abuse causes damage to structures within the human cerebrum, with particular susceptibility to white matter (WM). Abnormalities have been reported in anterior regions with less evidence of changes in posterior regions. Methamphetamine abusers have also shown deficits on attention tests that measure response conflict and cognitive control. METHODS We examined cognitive control with a computerized measure of the Stroop selective attention task and indices of WM microstructure obtained from diffusion tensor imaging (DTI) in the callosal genu and splenium of 37 currently abstinent MA abusers and 17 non-substance abusing control subjects. Measurements of fractional anisotropy (FA), apparent diffusion coefficient (ADC) of callosal fibers, and diffusion tensor eigenvalues were obtained in all subjects. RESULTS The MA abusers exhibited greater Stroop reaction time interference (i.e., reduced cognitive control) (p = .04) compared with control subjects. After correcting for multiple comparisons, FA within the genu correlated significantly with measures of cognitive control in the MA abusers (p = .04, Bonferroni corrected) but not in control subjects (p = .26). Group differences in genu but not splenium FA were trend significant (p = .09). CONCLUSIONS Methamphetamine abuse seems to alter anterior callosal WM microstructure with less evidence of change within posterior callosal WM microstructure. The DTI indices within the genu but not splenium correlated with measures of cognitive control in chronic MA abusers.