Rats explore their immediate environment by rapidly sweeping their vibrissae back and forth. For whisking, the sensory task of extracting information from the world is of necessity intertwined with the motor task of moving and positioning vibrissae. In order to investigate general principles of active sensation, this study proposes to determine the hierarchical sensorimotor control of whisking. The prevailing model for the generation of rhythmic whisking is that primary motor cortex (M1) sends control signals to a brainstem central pattern generator (CPG) that produces the actual pattern of muscle activation. Additionally, both M1 and the CPG are a part of a feedback system of nested sensorimotor loops. This study aims to (1) characterize the total number of phases of the brainstem CPG during a single whisk cycle and their dependence on sensory input via chronic EMG electrode implants in the facial muscles and nerve transection, (2) use simultaneous opotoelectronic monitoring of vibrissa motion to determine the detailed muscular control of the vibrissae, and (3) elucidate motor control in M1 through recordings of single units in awake, behaving animals. The combined results of these studies will produce a detailed model of how M1 and the subcortical CPG control whisking. An understanding of motor tasks is essential for understanding how such control can fail under disease and how function may be restored through interventional therapies. [unreadable] [unreadable] [unreadable]