How the basal ganglia forces cortex to do what it wants

It is well established that multiple brain areas are involved in generating movements, yet individual brain areas are often studied in isolation. A wealth of data indicates that the basal ganglia interact with the cerebral cortex and are important for movements. For example, diseases of the basal ganglia, such as Parkinson’s, cause profound movement disorders. Understanding the role of the basal ganglia in movements will therefore be critical to understanding movements in general, and to finding cures for movement disorders. Neurons in the basal ganglia and those in the cerebral cortex are intimately connected to each other, indicating that these two regions likely act together during movements. But what is the relationship between neuronal activity in the cortex and neuronal activity in the basal ganglia? Our goal is to understand this relationship in both monkeys and rodents. One idea is that the basal ganglia biases, or forces, the cortex to choose one action over another—especially an action that could lead to a reward. The basal ganglia’s known role in predicting rewards is consistent with such a relationship. We will test this possibility by using technology to record the activity of many neurons at once, and also to manipulate the activity of those neurons while the animals perform various movement-related tasks, such as reaching. In general, our work will shed light on how two major brain areas contribute to movements based on reward, paving the way for insights into movement disorders, such as Parkinson’s.