Our long-term goal is to understand the neural control of reaching to grasp. Reaching to grasp is essential to primate motor behavior and strongly depends on cerebellar function. Cerebellar damage causes decomposition of reach-to-grasp movements: the reach becomes inaccurate and uncertain, and hand preshaping occurs at highly variable times within the reach.
We use intermediate cerebellum, and its associated neural circuitry, as a model system for studying how the brain generates command signals for movements. We record signals transmitted by individual neurons in behaving monkeys. In addition, we study behavioral deficits resulting from reversible inactivation of specific cell groups, and we define relevant neural pathways anatomically. Our results support the hypothesis that intermediate cerebellar output via the rubrospinal tract is specialized for control of hand use: rubrospinal neurons may command muscle synergies that produce grouped digit extension to preshape the hand at the appropriate time within the reach.