Frontostriatal white matter integrity mediates adult age differences in probabilistic reward learning

Abstract

Frontostriatal circuits have been implicated in reward learning, and emerging findings suggest that frontal white matter structural integrity and probabilistic reward learning are reduced in older age. This cross-sectional study examined whether age differences in frontostriatal white matter integrity could account for age differences in reward learning in a community life span sample of human adults. By combining diffusion tensor imaging with a probabilistic reward learning task, we found that older age was associated with decreased reward learning and decreased white matter integrity in specific pathways running from the thalamus to the medial prefrontal cortex and from the medial prefrontal cortex to the ventral striatum. Further, white matter integrity in these thalamocorticostriatal paths could statistically account for age differences in learning. These findings suggest that the integrity of frontostriatal white matter pathways critically supports reward learning. The findings also raise the possibility that interventions that bolster frontostriatal integrity might improve reward learning and decision making.

Figures

Figure 1.

A–D, White matter tracts in a representative subject between the VTA-NAcc (A), NAcc-DMThal (B), DMThal-MPFC (C), and MPFC-NAcc (D). The thalamocortical (C) and corticostriatal (D) tracts were associated with both age (N = 25) and learning (N = 22). Scatter plots are simple pairwise correlations. E, A combined measure of thalamocorticostriatal (TCS) white matter integrity mediates age differences in probabilistic reward learning (N = 22). Path coefficients are standardized βs. *p < 0.05, two-tailed.