Working memory training impacts the mean diffusivity in the dopaminergic system

Abstract

Dopaminergic transmission plays a critical role in working memory (WM). Mean diffusivity (MD) is a sensitive and unique neuroimaging tool for detecting microstructural differences particularly in the areas of the dopaminergic system. Despite previous investigation of the effects of WM training (WMT) on dopamine receptor binding potentials, the effects of WMT on MD remain unknown. In this study, we investigated these effects in young adult subjects who either underwent WMT or received no intervention for 4 weeks. Before and after the intervention or no-intervention periods, subjects underwent scanning sessions in diffusion-weighted imaging to measure MD. Compared with no intervention, WMT resulted in an increase in MD in the bilateral caudate, right putamen, left dorsolateral prefrontal cortex (DLPFC), right anterior cingulate cortex (ACC), right substantia nigra, and ventral tegmental area. Furthermore, the increase in performance on WMT tasks was significantly positively correlated with the mean increase in MD in the clusters of the left DLPFC and of the right ACC. These results suggest that WMT caused microstructural changes in the regions of the dopaminergic system in a way that is usually interpreted as a reduction in neural components.

Keywords: Diffusion-weighted imaging; Dopamine; MRI; Mean diffusivity; Plasticity; Training; Working memory.

Fig. 1

Increase in mean diffusivity in the working memory training (WMT) group compared with the control group. Results are shown with a threshold of P < 0.05 and corrected for multiple comparisons at FDR within the regions of interest. Findings were overlaid on a “single-subject T1” SPM image. Bar represents the t score. The voxel-by-voxel analysis of covariance showed compared with the control intervention (no-intervention), WMT resulted in a significant increase in MD in nigrostriatal and mesocortical areas