Associations between different white matter properties and reward-based performance modulation.

Humans can be motivated by the prospect of gaining a reward. However, the extent to which we are affected by reward information differs from person to person. A possible mechanism underlying these inter-individual differences may be alterations in white matter (WM) microstructure; however, the relationship between WM properties and reward-based behaviour in healthy participants has not yet been explored. Here, we used a fixel-based approach to investigate potential associations between WM tracts and performance in a reward-cuing task. We found that WM properties in the corpus callosum, right uncinate fasciculus, left ventral cingulum, and accumbofrontal tracts were inversely related to reward-triggered performance benefits (indexed by faster reaction times). Moreover, smaller WM property values in the corpus callosum, uncinate fasciculus, and accumbofrontal tracts were associated with higher scores on the Behavioral Inhibition System scale, reflecting greater sensitivity to potential punishment. Finally, we also observed associations between functional hemodynamic activity in the ventral striatum and WM microstructure. The finding that reward-based behavioural benefits are related to lower measures of WM tracts is in contrast to studies linking higher WM metrics to superior cognitive performance. We interpret the current pattern in terms of higher susceptibility to motivationally relevant stimuli, which is in line with the current and previous studies reporting inverse relationships between WM properties and motivational traits. Taking a broader perspective, such propensities may only be beneficial up to a certain point, at which these may become detrimental to performance and even manifest as impulsive and addictive behaviour.