The nervous system functions through a network of neural connections. We seek to understand which neural connections are critical for skilled movement, particularly of the arm and hand. We focus on the sensory and motor circuits that connect the brain and spinal cord. Motor connections include the corticospinal tract, the direct connection between cortex and the spinal cord, as well as rely pathways through the brain stem. These motor circuits interact strongly with sensory circuits that code for limb position and muscle length and tension among others. The interplay between descending motor connections and sensory connections is particularly robust in the spinal cord, and we think this interaction may be key for movement in health and for recovery of movement after injury. A key question is which neural circuits should be targeted for recovery. To address this, we have used viral methods to label and manipulate specific neural connections to understand their role in endogenous recovery after injury. We also use targeted electrical stimulation to promote specific connections, and particularly the interaction of sensory and motor connections in the spinal cord. The overall approach is to develop an understanding of the neural networks that should be recruited for nervous system repair.