White matter integrity in the fronto-striatal accumbofrontal tract predicts impulsivity.

Frontostriatal projections have been shown to mediate impulsivity. Recent findings have demonstrated that the projection from the prefrontal cortex to the nucleus accumbens (the accumbofrontal tract) can be isolated by using probabilistic tractography on human brain MRI data, specifically, diffusion tensor images (DTI). Using DTI tractography, we isolated the tract and tested its association with the impulsivity. DTI data from 143 individuals obtained from Nathan Kline Institute-Rockland Sample was used along with the impulsivity measure assessed by the UPPS (urgency, premeditation, perseverance, and sensation seeking) impulsive behavior total score. Probabilistic tractography was first performed between the prefrontal cortex and nucleus accumbens, then, as a measure of white matter integrity in the tract, fractional anisotropy was calculated for each individual's tract. In the multiple regression, accumbofrontal FA showed significant positive association with the impulsivity, suggesting that the accumbofrontal tract integrity may contribute to individual differences in impulsivity. This study bridges the literature in rodents, in which this glutamatergic projection has been shown to mediate impulsive behavior, and the findings in humans which allow the in-vivo isolation of the tract and comparison with behavior.