ABSTRACT
The study of the cerebellar granule cell has led to significant neurobiologic advances in a broad range of areas that include developmental neurobiology, neurotransmitter activity, neuronal apoptosis and genetic and biochemical neuropathology. Because of its distinctive pattern of cellular and molecular layers as well as its morphologically unique cell types, the cerebellar cortex has long been an important experimental model for brain cell organization and function. Included among the features extensively studied dating as far back as Cajal (1911) are neuronal proliferation, migration, neuritogenesis, synaptogenesis and neurotransmitter function. Theoretical modeling has also been applied in an effort to characterize and understand complex brain function from a neural circuitry perspective (Baev, 1997). The understanding of cerebellar function derived initially from ablation studies in animals. Rolando (1823) determined that motor activity but not sensory, intellectual and vital autonomic function was associated with the cerebellum. Subsequently, Flourens (1842) established that the cerebrum was responsible for initiating and directing motor activity and that the cerebellum performed a regulatory role in coordinating motor functions. Cerebellar ablation studies in mammals revealed that the cerebellum exerts an inhibitory effect on brainstem postural mechanisms. These effects serve to fine-tune movements, increasing accuracy and reproducibility. The inhibitory (GABA) neurotransmission exerted by Purkinje cells on vestibular and deep cerebellar nuclei is the primary effector pathway for this motor regulatory action. Purkinje cells in turn are activated by climbing fibers from the olivocerebellar pathway and parallel fibers emanating from the granule cell.
