The basal ganglia mediate the inter-hemispheric transfer of complex tool-use skill.

Motor skills learned in one hand generalize to the other hand via plastic changes in motor systems. Such "intermanual transfer" may arise during complex tool-use learning, but its neural underpinnings remain unknown. Using resting-state fMRI, we explored neurobehavioral effects occurring while right-handed participants were trained to use a novel complex tool with their left hand. Behaviorally, training improved tool-use performance equally for both hands, demonstrating a robust effect of intermanual transfer. For both hands, this behavioral effect correlated with functional connectivity changes between right dorsal premotor cortex (PMd) and intraparietal sulcus (IPS). For the untrained right hand, additional change emerged in right basal ganglia (BG), which showed increased behavior-connectivity correlation with bilateral PMd. Thus, tool-use skill learned by left-hand training is represented in the right PMd-IPS network and transferred to left PMd responsible for right-hand performance, pointing to a pivotal role of BG in generalizing complex tool-use skill across hands.