Structural projections to the nucleus accumbens link to impulsive components of human risk preference

Functional responses in the Nucleus Accumbens (NAcc) to risk- and reward-relatedcues can predict real-life risk-taking behavior. Since NAcc activity depends onneurotransmission from connected brain regions, projections to the NAcc may alsopredict risk preference. To quantify risk preference, we employed latentvariables previously derived in a comprehensive, independent study examining thepsychometric structure of risk preference, which yielded a general riskpreference factor as well as several specific factors, including a factorcapturing impulsivity. Informed by previous work, we preregistered a set ofhypotheses concerning the association between different risk preference factorsand fractional anisotropy (or FA, which is sensitive to fiber coherence) forprojections to the NAcc from Medial PreFrontal Cortex (MPFC), Anterior Insula,Amygdala, and an inferior tract from the Ventral Tegmental Area (iVTA). Wetested our hypotheses in a community sample of 125 healthy human adults. Aspredicted, bilateral iVTA-NAcc tract FA showed a negative correlation with apsychometric factor that captured impulsivity, generalizing findings from priorresearch. Also as predicted, FA of the bilateral Amygdala-NAcc tract waspositively associated with the impulsivity factor. Contrary to predictions,however, we observed no robust associations between the general risk preferencefactor and FA for projections from bilateral MPFC, right Anterior Insula, orbilateral Amygdala to the NAcc. Notably, exploratory unilateral analysesrevealed an association between the general risk preference factor and leftMPFC-NAcc tract FA. Taken together, these findings suggest that impulse controlas a facet of risk preference maps onto specific neurobiological targets, whilemore general facets of risk preference may be supported by structural propertiesof lateral fronto-striatal projections. Although the exact associated functionalmechanisms remain to be fully clarified, conNAcctomic approaches like the onepresented here could pave the way for further research into the physiologicalfoundations of risk preference and related constructs.