At the current time, we know very little about the structural changes that might mediate the differences in impulsivity and risky choice between cocaine users and nonusing controls. However, some of the deficits described previously appear to relate to white matter integrity as measured by diffusion tensor imaging (DTI). Moeller and colleagues (2005) report that cocaine-dependent individuals exhibited reduced fractional anisotropy (FA) in the anterior corpus callosum compared to controls. Within the cocaine dependents, the reduction in FA significantly correlated with errors of commission on a continuous performance test (Moeller et al., 2005). In addition, cocaine abusers showed increased radial diffusivity, which has been associated with altered myelin in animal studies (Moeller et al., 2007). The same authors, using a different sample of cocaine dependents, have replicated the finding of reduced FA in the corpus callosum in cocaine abusers and shown that severity of drug use is related to reduction in FA (Ma et al., 2009).
