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Purkinje cells and the cerebellum share a mutual existence. These large neurons reside in the cerebellum, where they help to regulate motor movement. There are large numbers of dendrites arranged in a treelike structure found in Purkinje cells. Dendrites receive information from other neurons, and instruct the cell whether or not it should relay a message to other neurons.
The cerebellum is arranged in multiple levels, with Purkinje cells located at the deepest level. These specialized cells receive information from all other levels, and integrate input from the rest of the cerebellum. The Purkinje cells are the cerebellum's only output source. There is an important connection between Purkinje cells and the cerebellum, since these cells let this area send messages to the rest of the brain.
In addition to coordinating information from the cerebellum, Purkinje cells also receive signals from other brain areas and the spinal cord. These signals are thought to contain sensory information and motor planning signals that could influence motor movement. Most of these signals are excitatory, which means they encourage the recipient cell to pass along its own signal. Purkinje cells transmit inhibitory signals, however, which could give a clue as to their role.
The exact way that Purkinje cells and the cerebellum function together is not yet fully understood. The cerebellum may utilize these cells as a sort of interpreter. Purkinje cells receive direct and indirect excitatory input from the brain stem, spinal cord, and medulla, but have inhibitory output. This fact has led researchers to theorize that Purkinje cells arrange this large volume of information and integrate it. They weed out background noise and send out comprehensible messages containing only essential content to the rest of the brain.
Clues to the relationship between Purkinje cells and the cerebellum can be found by studying diseases that affect these cells. Cerebellar abiotrophy is a disease that kills Purkinje cells around the time of birth. Animals with this disease show a lack of awareness of their limb position when walking, uncoordinated movement, tremors, problems with evaluating distance, and abnormal gait when walking.
Some diseases seen in humans, like Niemann-Pick disease, can cause similar symptoms. These particular symptoms point to the Purkinje cells integrating information relating to the spatial orientation of the body, control and coordination of motor movements, and the relative positions of body parts. The Purkinje cells and the cerebellum therefore work together to compile volumes of information, and instruct the body how to coordinate movements based on this information.