Distribution of olivocerebellar fibers demonstrated by a radioautographic tracing method.

The method of injecting radioactive amino acids for the marking of neurons and the demonstration of their terminals by means of radioautography has been applied to the olivocerebellar projection. After injections in the olive, labeled fibers were observed in the molecular layer of the cerebellar cortex. The projections were distributed in specific regions of the cerebellum, depending on the position of the injections within the nucleus. A comparison of that topographical arrangement with Brodal's chart of olivocerebellar distribution indicates a close correspondence. In addition, the olivocerebellar climbing fibers terminate as a series of strips oriented perpendicularly to the long axes of the folia. In all regions observed so far, the strips of the projection alternate with empty spaces of the same width. It is postulated that another group of climbing fibers originating outside the olive interdigitate with the olivocerebellar fibers.