Neural circuits underlying the acquisition and control of motor skills Much of our behavioral repertoire consists of learned motor skills, yet little is known about the neural mechanisms that underlie their acquisition and execution. We have recently discovered that motor cortex is required for learning but not for executing certain motor skills, suggesting an autonomous subcortical motor network capable of generating task-specific learned motor sequences. Importantly, motor cortex seems to be involved in ‘tutoring’ this subcortical network during learning. Here we will first explore the role of the basal ganglia, a collection of motor-related midbrain nuclei of great clinical significance, in the storage and execution of complex task-specific motor sequences. Specifically, we will test whether the part of the basal ganglia that receives input from motor cortex, the dorsolateral striatum (DLS), is essentially involved in producing the skills we train. We will do this by way of lesioning DLS and other parts of the basal ganglia in animals that have learned to master the task we train (Aim 1). We will further analyze how the striatum encodes the learned motor sequences, specifically testing the hypothesis that it encodes the detailed structure and kinematics of learned motor sequences (Aim 2). Lastly, we will test the idea that motor cortex is ‘tutoring’ the subcortical motor circuits during learning through its projections to the basal ganglia (Aim 3). We will explore these questions using a fully automated rodent training system we developed, in combination with a set-up for recording neural activity and behavior continuously over weeks and months in freely behaving rodents. Addressing the aims of our proposal will clarify the logic of how the mammalian motor system acquires and controls task-specific motor sequences, and delineate the roles of the BG and the corticostriatal pathway in these important processes, thus addressing fundamental questions in neuroscience with far-reaching implications for clinical practice and neurorehabilitation.