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. (shrink)

Starting from macroscopic and microscopic facts of cerebellar histology, we propose a new functional interpretation that may elucidate the role of the cerebellum in movement control. The idea is that the cerebellum is a large collection of individual lines (Eccles's : Eccles et al. 1967a) that respond specifically to certain sequences of events in the input and in turn produce sequences of signals in the output. We believe that the sequence-in/sequence-out mode of operation is as typical for the cerebellar cortex (...) as the transformation of sets into sets of active neurons is typical for the cerebral cortex, and that both the histological differences between the two and their reciprocal functional interactions become understandable in the light of this dichotomy. The response of Purkinje cells to sequences of stimuli in the mossy fiber system was shown experimentally by Heck on surviving slices of rat and guinea pig cerebellum. Sequential activation of a row of eleven stimulating electrodes in the granular layer, imitating a of the stimuli along the folium, produces a powerful volley in the parallel fibers that strongly excites Purkinje cells, as evidenced by intracellular recording. The volley, or has maximal amplitude when the stimulus moves toward the recording site at the speed of conduction in parallel fibers, and much smaller amplitudes for lower or higher The succession of stimuli has no effect when they in the opposite direction. Synchronous activation of the stimulus electrodes also had hardly any effect. We believe that the sequences of mossy fiber activation that normally produce this effect in the intact cerebellum are a combination of motor planning relayed to the cerebellum by the cerebral cortex, and information about ongoing movement, reaching the cerebellum from the spinal cord. The output elicited by the specific sequence to which a is tuned may well be a succession of well timed inhibitory volleys the motor sequences so as to adapt them to the complicated requirements of the physics of a multijointed system. (shrink)

Leiner, Leiner, and Dow proposed that the co-evolution of cerebral cortex and the cerebellum over the last million years gave rise to the unique cognitive capacities and language of humans. Following the findings of recent imaging studies by Imamizu and his colleagues, it is proposed that over the last million or so years language evolved from the blending of decomposed/re-composed contexts or "moments" of visual-spatial experience with those of sound patterns decomposed/re-composed from parallel context-appropriate vocalizations . It is further proposed (...) that the adaptive value of this blending was the progressively rapid access to the control of detailed cause-and-effect relationships in working memory as it entered new and challenging environments. Employing the complex syntactical sequence of nut-cracking among capuchin monkeys it is proposed how cerebro-cerebellar blending of low-volume vocalization and visual-spatial working memory could have produced the beginnings of the phonological loop as proposed by Baddeley, Gathercole, and Papagno. It is concluded that the blending of cerebellar internal models in the cerebral cortex can explain the evolution of human advancements in the manipulation of cause-and-effect ideas in working memory, and, therefore, the emergence of the distinctive "cognitive niche" of humans proposed by Tooby and DeVore and supportively elaborated by Pinker. (shrink)