Abstract: This article reviews models of the cerebellum and motor learning, from the landmark papers by Marr and Albus through those of the present time. The unique architecture of the cerebellar cortex is ideally suited for pattern recognition, but how is pattern recognition incorporated into motor control and learning systems? The present analysis begins with a discussion of exactly what the cerebellar cortex needs to regulate through its anatomically defined projections to premotor networks. Next, we examine various models showing how the microcircuitry in the cerebellar cortex could be used to achieve its regulatory functions. Having thus defined what it is that Purkinje cells in the cerebellar cortex must learn, we then evaluate theories of motor learning. We examine current models of synaptic plasticity, credit assignment, and the generation of training information, indicating how they could function cooperatively to guide the processes of motor learning.

Introduction

Lesion studies carried out in the nineteenth century demonstrated that the cerebellum is important for coordinating movements (Florens 1824). Mechanistic models of the cerebellum, however, awaited an analysis of its histology (Braitenberg & Atwood 1958) and combined analyses of its histology and electrophysiology (Albus 1971; Marr 1969). The clear orthogonal relationships between parallel and climbing fibers and the dendritic trees of Purkinje cells (PCs) convinced Braitenberg that the cerebellum functions as a timing organ.