Grant: Project Grant

Rewards play a critical role in shaping behaviors and learning, including motor learning and re-learning after stroke. The motor cortex is the main command center for skilled voluntary forelimb movement and is engaged in motor learning and adaptation. However, the influence of the brain reward centers on the motor cortex are poorly known. Here, we propose to investigate the role of dopamine centers, which are involved in reward processing, on motor learning, plasticity, and motor recovery after stroke. Learning dextrous motor actions, such as playing darts, requires a lot of practice. This engages the motor cortex. During the early process, we make frequent mistakes; darts are scattered and end up far away from the bullseye. But with time, we get more precise and accurate. Why is it that we improve? Why are successful actions reinforced more so than mistakes? The mechanism is thought to involve reward signals, indicating precisely when a preceding motor action should be reinforced. This learning signal, when playing darts, may take the form of a brief release of dopamine in the motor cortex after that perfect throw. The ventral tegmental area (VTA) is a well-studied reward center, containing neurons releasing dopamine which are strongly activated in rewarded contexts. These neurons influence learning and plasticity in several brain structures. However, very little is know about their anatomical properties and their influence on the motor cortex. Here, we propose to precisely characterize the anatomy of the dopaminergic inputs to the motor cortex in rats, and reveal their influence on motor learning and motor recovery in a stroke model. The proposed work will provide clear evidence of the critical influence of dopamine on motor cortical function from a number of complementary approaches. Our investigation will answer questions that may ultimately contribute to the development of more effective neurorehabilitation after stroke.