Axons projecting from neurons in the inferior olivary nucleus in the medulla impinging multiple synapses directly on Purkinje cells in the cerebellum (up to 300 on each of the dendrites of these cells), and which contain the neurotransmitter aspartate. They wind among Purkinje cell dendrites, and have a powerful and specific input to the Purkinje cell, thereby providing direct input to the only cell in the cerebellum that has a direct output. In fact, they have a powerful and strong input to the Purkinje cell, with one fiber connecting a small number of such cells. In contrast, the mossy fiber-parallel fiber system is weak and divergent, with each parallel fiber innervating a large number of Purkinje cells. One of two afferent fiber inputs to the cerebellum, they transmit rhythmical oscillations or action potentials controlled by the other fiber inputs (viz., mossy fibers) that dominate the activity of Purkinje cells.
See Action potential, Aspartate (or aspartic acid), Cerebellum (anatomy), Cerebellum (functions), Inferior olive (or olivary) nucleus, Mossy fibers, Neurotransmitters, Purkinje cells