Extended Practice of a Motor Skill Is Associated with Reduced Metabolic Activity in M1

How does long-term training and the development of motor skill modify the activity of the primary motor cortex (M1)? To address this issue we trained monkeys for ~1–6 years to perform visually-guided and internally-generated sequences of reaching movements. Then, we used (14)C-2-deoxyglucose (2DG) uptake and single neuron recording to measure metabolic and neuron activity in M1. After extended practice, we observed a profound reduction of metabolic activity in M1 for the performance of internally-generated compared to visually-guided tasks. In contrast, measures of neuron firing displayed little difference during the two tasks. These findings suggest that the development of skill through extended practice results in a reduction in the synaptic activity required to produce internally-generated, but not visually-guided sequences of movements. Thus, practice leading to skilled performance results in more efficient generation of neuronal activity in M1.