FUNCTIONAL ORGANIZATION OF CEREBELLAR OUTPUT

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DESCRIPTION (Investigator's Abstract): Our long-range goal is to understand the role of the cerebellum in the control of reaching to grasp an object. The "reach to grasp" is a basic movement used in daily activities, and production of a coordinated "reach to grasp" is highly dependent upon cerebellar function. Analyzing cerebellar participation in the "reach to grasp" will lead to a much better understanding of the organization of the entire motor system and may provide valuable guidance to the design of prosthetic devices attempting to compensate for impaired motor control. We have discovered that cerebellar circuitry is specialized for the control of a "reach to grasp". Simple movements of the forelimb do not activate circuity of intermediate cerebellum, but the coordinated action of reaching and grasping elicits high rates of neural discharge. We have also discovered that regions of the cerebellum are specialized for the control of specific components of the "reach to grasp". Intermediate cerebellum only participates in the control of the grasping component and not the transport component of the movement. There are two overall aims of this proposal: one is to define the movements that are included in the grasp component controlled by intermediate cerebellum, and the other is to determine if the medial nucleus of the cerebellum controls the transport component. By determining whether or not discharge is dependent upon the type of hand movement and/or the accompanying upper arm supporting movements, we will learn if intermediate cerebellum controls only hand movement or movements of the entire limb that accompany specific hand movements. A series of tracking and reaching to grasp test will also be performed on units recorded from medial nucleus to determine of medial nucleus is involved in the control of the transport component. Additionally, we will use reversible inactivation of specific nuclear regions to see if resulting behavioral deficits match the conclusion that we have reached from the recording experiments.