Mapping Striatal Unit Activity Related to Behavior and Dopamine

Despite abundant pathological evidence indicating that the striatum, a brain structure (caudate-putamen) is an important component of the motor system, little is known about the physiology of the striatum during normal behavior. This is true for several reasons. First, the use of anesthesia in physiological experiments, while allowing progress in understanding other regions of the brain has obscured our understanding of the striatum due to its drastic reduction in neuronal activity in this system. Furthermore, anesthetics have been shown to alter measures of dopaminergic function in the striatum (as compared with awake animals). Second, unit recordings from single striatal neurons in awake animals have seldom shown the clear, consistent correlations with motor and sensory events typical of neurons in primary motor and sensory areas. Instead responses, when present, are conditional and the details regarding the necessary conditions remain unknown. Third, single unit recordings during conscious behavior have been restricted almost entirely to the primate during head restraint. The involvement of the striatum in movement could, however, encompass a broader integration of whole body sensorimotor processing. Coordinated active movement is achieved both by causing rotational and translational movement of joints (primary movement), and by stabilizing other body parts and shifting the center of gravity so that the primary movement can occur. It is possible that conditions allowing unrestrained movement and the accompanying sensory feedback may be required for full manifestation of striatal participation in such processes. If so, electrophysiological recordings in freely moving animals, may reveal previously unobserved features elucidating the unique contribution of the striatum and basal ganglia to behavior. Dr. Mark West will study the role of the behavior of the striatum in awake, intact, unanesthetized animals.