Large efferent neurons in the middle layer of the cerebellar cortex, packed together in the Purkinje cell layer directly under the molecular layer, that process the input from parallel and climbing fibers. Their inhibitory GABA axons, projecting to the deep cerebellar nuclei, provide the sole output from the cerebellum. This output has a relatively high rate of action potentials at rest, amounting to some 50-100 per second. However, the output is not continually inhibitory as it is regulated and focused by inhibitory interneurons of the cerebellar cortex (a process known as ‘sharpening of the focus’ or ‘focusing effect’). They have inhibitory influences on the vestibular nuclei, are excited by the parallel and climbing fibers, and inhibited by basket and stellate cells. The number of Purkinje cells varies between 15 to 26 million, with each one having up to 200,000 synapses with parallel fibers (and each one of them coming from a different granule cell). They have a massive, espalier-like (lattice work) dendritic aborization that sends its branches to the molecular layer in a plane perpendicular the long axis of the folium. It is so massive that if the dendritic surface of a Purkinje cell was flattened out, it would cover two averaged-size doors. Discovered by Johannes E. Purkinje (1787-1869) in 1837.
See Action potential, Autism, Basket cells, Cerebellar cortex, Cerebellum (anatomy), Climbing fibbers, Deep cerebellar nuclei, Gamma amino butyric acid (GABA), Interneurons, Mossy fibers, Parallel fibers, Purkinje cell layer, Vestibular nuclei