What is the Cerebellar Cortex?

The cerebellar cortex is the thin crumpled gray neural tissue that makes up the outer layer of the cerebellum. The cerebellum is at the base of the brain and is considered to reign over fine motor control. Since the introduction of new neural imaging technology in the late 1980s and early '90s, scientists have been able to investigate the cerebellar cortex's role beyond mere motor control. It is widely believed to participate in cognitive and linguistic functions as well.

The cerebellum is tucked away just underneath the two hemispheres of the cerebrum, the wrinkled bulbous mound that most people think of as the brain. Like the cerebrum, the cerebellum divides itself into two hemispheres and is covered by a wrinkled outer layer of gray neural tissue. In the cerebellum, this tissue is called the cerebellar cortex. Unlike the disorganized appearance of the cerebral cortex, the cerebellar cortex's folds run in a network of tight, parallel grooves.

The cerebellar cortex consists of three layers: the stratum granulosum, the ganglionic layer and the stratum moleculare. The thickest and innermost layer, the stratum granulosum, is named for the tiny granule cells that populate it. These cells are so small and crowded together that the cerebellum contains more neurons than the rest of the brain combined. The middle ganglionic layer is made up of purkinje cell bodies, large neurons responsible for most of the electrical activity in the cerebellum. The stratum moleculare, the outer molecular layer, is made up of the flattened dendrites of the purkinje cells connected to each other by a vast array of parallel fibers.

As the largest, most neuron-rich component of the cerebellum, the cerebullar cortex plays an integral role in fine-tuning motor controls. People and animals with cerebellar damage can still perform normal motor skills, but they frequently accomplish those movements in a slow and jerky way. For example, when reaching for an object, a person with a normally functioning cerebellum moves his or her hand straight out toward the object without any hesitation or correction after the movement has begun. A person who has cerebellar damage, however, reaches out much more slowly and with erratic corrections during the entire course of the movement.

In the early 1990s, new neural imaging technology made it possible to study the cerebral cortex's role in functions not related to the motor system. Evidence collected from studies in the years that followed suggests that the cerebellar cortex also contributes to cognition, language and emotion. In addition to fine movement idiosyncrasies, people who have cerebellar cortex damage report impairments to multitasking abilities, linguistic processing and mood.