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 circuits underlying their acquisition and control. The overarching goals of our research program is to identify these circuits, delineate their respective functions, and explain the logic by which they work together to implement motor skill learning and execution. To work towards this goal, we developed cutting-edge experimental infrastructure designed to enable high-throughout and rigorous studies of complex learned behaviors in rodents. To facilitate the study of learned motor skills, we developed a task that train rats to produce task-specific movement patterns with complex learned movement kinematics. In previous work, we showed that motor cortex is necessary for learning these skills, but not for executing them once acquired. These surprising results suggest that, while motor cortex has a function in learning, the acquired skills are stored and generated subcortically. We further showed that the sensorimotor input region of the basal ganglia, the dorsolateral striatum, encodes the kinematic details of the learned motor skills and is essential for generating them. Here, we build on these results to examine the logic and mechanisms by which subcortical circuits, specifically the striatum and thalamus, contribute to acquiring, storing, and generating these skills. To get at this, we will use our innovative experimental platform to monitor neural activity and behavior continuously over weeks of training, while also perturbing neural activity and observe the effects of these manipulations on behavior. We will describe how striatal encoding of task-related movement patterns changes with learning and how these changes relate to a striatum’s putative control function (Aim 1). We will further parse the pathways from thalamus to striatum that are relevant for motor skill execution (Aim 2) and describe task-related activity patterns in the thalamus and how they are transformed in the striatum (Aim 3). Precise measurement of the rats’ movements using video-based motion tracking will relate our neural recordings and circuit manipulations to behavior in exact ways, allowing us to infer how subcortical circuits implement the acquisition and execution of learned skills. Addressing these aims will clarify the logic of how the mammalian motor system enables motor skill learning and execution and delineate the roles of the basal ganglia and thalamus in these important processes, thus addressing fundamental questions in neuroscience with far-reaching implications for clinical practice and neurorehabilitation.