Modulation of neurometabolites in sensory processing brain areas during motor learning

GABA and glutamate (Glu) play pivotal roles in learning. Here, we investigated whether neurometabolites in specific sensory processing brain areas were differentially modulated depending on the type of feedback provided during motor learning and whether this was associated with behavioural progress. Fifty healthy human adults were trained on a bimanual tracking task for 5 days (Day 1 to Day 5) when receiving either concurrent (CA-VFB) or terminal (TA-VFB) augmented visual feedback. In two brain areas involved in sensory processing, that is the primary somatosensory cortex (S1) and medial temporal visual area (MT/V5), concentrations of GABA+ (GABA + macromolecules) and Glx (Glu + glutamine) were determined by acquiring magnetic resonance spectroscopy at three time points on Day 1 and Day 5: baseline (Pre-Scan), during (Mid-Scan) and after (Post-Scan) task training. Behaviourally, performance progress was more pronounced on Day 1 compared to Day 5. Neurochemically, there was a significant difference in the modulation of neurometabolites between the S1 and MT/V5 regions, specifically in Glx levels on Day 1. Additionally, there was a significant difference in the modulation of neurometabolites between Day 1 and Day 5, specifically in GABA+ levels in the S1 area and Glx levels in the MT/V5 area. Furthermore, a greater increase in individual S1 Glx levels on Day 5 correlated with larger behavioural progress. Our findings suggest that neurometabolites in task-related sensory processing brain areas show a differential modulation and contribute to long-term retention of visuomotor learning. KEY POINTS: GABA and glutamate play crucial roles in motor learning, yet how these neurometabolites are modulated within specific sensory processing brain regions based on the type of feedback provided during different phases of motor learning remains unclear. We used a repeated measures magnetic resonance spectroscopy design to measure the concentration of neurometabolites in the primary somatosensory cortex (S1) and medial temporal visual area (MT/V5) before, during and after motor training, focusing on the initial and late learning phases. In the initial learning phase, Glx (glutamate + glutamine) modulation differed between S1 and MT/V5. Furthermore, in S1, GABA modulation differed between the initial and late phases, and, in MT/V5, Glx modulation also varied between these phases. A greater increase in individual S1 Glx levels on Day 5 correlated with larger behavioural progress. These findings suggest that distinct biological changes occur in task-related sensory processing areas across different phases of motor learning.