The proposed research is a continuation of a long-term project to understand the organization in the cerebellar cortex of tactile information from the entire body surface as conveyed by the climbing fiber (CF) system. The proposed studies will examine the CF organization in several lobules of the cerebellum in cats (lobules VII to X, Crus I and II) and monkeys (lobule IV) anesthetized with sodium pentobarbital as well as in unanesthetized monkeys (lobules IV to VI). Multiple tungsten microelectrode penetrations will be made in each animal and extracellular CF responses will be recorded from individual Purkinje cells. Each response will be evaluated with natural tactile stimuli, and selected responses will be tested with a computer controlled mechanical stimulator. The main parameters to be examined will be: modality of the stimuli, force thresholds, and receptive field properties. Histological recostruction of the electrode penetrations will provide the localizaton of responses within the cortex. Acetylcholinesterase staining of cerebellar tissue will provide a comparison between the CF response properties and anatomically defined parasagittal zones. In monkeys prepared for chronic recording similar CF response properties will be studied. A comparison of the receptive field features will be made in the presence and absence of anesthetic. An analysis of receptive field features obtained from all the experiments will be used to develop a mathematical model of CF representation. An attempt will be made to determine how skin location information is encoded in different lobules and between different species. The proposed studies of the CF system will provide the first complete description of: (1) the spatial distributon of body surface representation throughout the cerebellar cortex, (2) the degree of cortical representation for various body surfaces, (3) the receptive field characteristics and the influence of an anesthetic on these characteristics, and (4) the extent of homogeneity in body surface representation for the anterior lobe between the cat and monkey. Such information is essential in order to understand what the CF system is encoding and how multiple representation of different body surfaces in various areas of the cerebellar cortex influences motor functions. These proposed studies will make an important contribution to the formulation of new theories of cerebellar function.
