Distinct basal ganglia territories are engaged in early and advanced motor sequence learning

TLDR

The study aimed to map the temporal evolution of basal ganglia activation during explicit learning of a finger‑movement sequence over one month of training. Fourteen right‑handed volunteers practiced an eight‑move sequence with their left hand for 15 min daily, with fMRI scans on days 1, 14, and 28 to capture neural activity. Activation decreased in associative putamen regions while increasing in sensorimotor putamen, with early‑learning activity correlating positively with error rate and advanced‑learning activity correlating negatively with reaction time, indicating a shift of motor representations from associative to sensorimotor basal ganglia territories.

Abstract

In this study, we used functional MRI (fMRI) at high field (3T) to track the time course of activation in the entire basal ganglia circuitry, as well as other motor-related structures, during the explicit learning of a sequence of finger movements over a month of training. Fourteen right-handed healthy volunteers had to practice 15 min daily a sequence of eight moves using the left hand. MRI sessions were performed on days 1, 14 and 28. In both putamen, activation decreased with practice in rostrodorsal (associative) regions. In contrast, there was a significant signal increase in more caudoventral (sensorimotor) regions of the putamen. Subsequent correlation analyses between signal variations and behavioral variables showed that the error rate (movement accuracy) was positively correlated with signal changes in areas activated during early learning, whereas reaction time (movement speed) was negatively correlated with signal changes in areas activated during advanced learning stages, including the sensorimotor putamen and globus pallidus. These results suggest the possibility that motor representations shift from the associative to the sensorimotor territories of the striato-pallidal complex during the explicit learning of motor sequences, suggesting that motor skills are stored in the sensorimotor territory of the basal ganglia that supports a speedy performance.