Cortical correlates of learning in monkeys adapting to a new dynamical environment

In this paper, we describe the neural changes observed in the primary motor cortex of two monkeys while they learned a new motor skill. The monkeys ha d to adapt their reaching movements to external forces that interfered with the execution of their arm movements. We found a sizable population of cel ls that changed their tuning properties during exposure to the force field. These cells took on the properties of neurons that are involved in the con trol of movement. Furthermore, the cells maintained the acquired activity a s the monkey readapted to the no-force condition. Recent imaging studies in humans have reported the effects of motor learning in the primary motor co rtex, Our results are consistent with the findings of these studies and pro vide evidence for single-cell plasticity in the primary motor cortex of pri mates.