As part of the vertebrate brain, the cerebellum has many important functions in controlling motor function. Damage to the cerebellum manifests in specific symptoms according to the affected area and extent.
What is the cerebellum?
Schematic diagram showing the anatomy and structure of the brain. Click to enlarge. The cerebellum, Latin for cerebellum, is located in humans below the cerebrum and behind the brain stem in the posterior fossa. It is the second largest part of the brain after the cerebrum, but has a higher cell density and significantly more neurons than the cerebrum. Although the cerebellum has only about 10 percent of the weight of the cerebrum, its numerous fine convolutions give it a surface area equivalent to 50 to 75 percent of the cerebrum. It is separated from the cerebrum by the cerebellar tent, called the tentorium cerebelli. The cerebellum is connected to the brainstem by three cerebellar peduncles, the pedunculus cerebellaris inferior, pedunculus cerebellaris medius and the pedunculus cerebellaris superior. The cerebellum performs important functions in the coordination and fine-tuning of body movements and in learning processes.
Anatomy and structure
The cerebellum consists of two hemispheres that bulge out on either side of the so-called vermis, Latin for vermis. The outer layer of the cerebellum is called the cortex or cortex. Inside the cerebellum is a white substance called the medulla or medulla. To increase surface area, the cortex of the cerebellum contains leaf-shaped bulges called folia cerebelli and is intersected by furrows called fissurae cerebelli. The two hemispheres divide anatomically by two furrows into three main lobes. These are called the lobus anterior cerebelli, lobus posterior cerebelli, and lobus flocculonodularis. However, the cerebellum can also be functionally divided into three areas: The vestibulocerebellum is associated with the organ of balance and corresponds anatomically to the lobus flocculonodularis’. The spinocerebellum receives information from the spinal cord and corresponds to the lobus anterior. The pontocerebellum is connected by fibers to the cerebrum and corresponds to the lobus posterior.
Function and tasks
The cerebellum works unconsciously; conscious control is not possible. The main function of the cerebellum is to control motor function. In addition, the cerebellum plays an important role in the learning of movement sequences. However, researchers now also believe that the cerebellum is involved in cognitive processes such as communication, social behavior, and visual perception. In addition, the cerebellum has been shown to be activated in various other tasks such as short-term memory, control of impulsive behavior, pain, hunger and respiratory distress, and other activities. However, the exact tasks of the cerebellum for this, in contrast to motor functions, have not yet been clarified in detail. For motor functions, different areas of the cerebellum perform different tasks. The vestibulocerebellum controls the holding and supporting motor functions. It is also responsible for the fine tuning of eye movements. It receives the necessary information about the position of the body and movement through the organ of balance. The spinocerebellum is responsible for stance, gait and support motor functions. In addition, it takes over tasks of the target motor function and the execution of movements. Through this, a movement can proceed as planned and targets, for example when reaching for objects, can be hit precisely. In addition, the spinocerebellum is important for the coordination of mimic and laryngeal muscles, which are needed for speech. It receives its information through fibers of the spinal cord. The pontocerebellum, the largest part of the cerebellum, is responsible for the fine planning and coordination of movements. It develops movement designs further, coordinates this and modulates them or corrects the movement planning. It receives its information through what is called the bridge, a section of the brain stem.
Diseases and disorders
Various diseases can lead to damage or dysfunction of the cerebellum. These include brain tumors, abscesses, inflammation, or metabolic diseases. Poisoning, for example in alcohol abuse, can also affect the cerebellum, as can injuries from an accident or genetic diseases.Dysfunction of the cerebellum usually results in problems with motor function, the symptoms of which depend on the location in the cerebellum and the size of the affected area. The symptoms are often grouped under the term ataxia. In ataxia, coordination of movements and posture are disturbed. Balance problems occur and gait may be unsteady. Movements are uncontrolled and often go beyond the target. If only one side of the body is affected by ataxia, it is called hemiataxia. In asynergia, coordination is also affected. Different muscle groups cannot act together properly, especially in finer movements. In dysdiadochokinesia, there is a decrease in coordination abilities, a rapid sequence of antagonistic movements can no longer be performed correctly. With dysfunction of the cerebellum, disorders of gaze stabilization can occur with eye tremor, called nystagmus, and saccadic gaze sequence. In saccadic gaze tracking, the eyes do not move fluidly when looking quickly to one side, but pause briefly in between each time before moving further to the side. There may be a reduction in muscle tension so that the entire body appears limp, or there may be an intention tremor, which is particularly evident in trembling hands when reaching for objects. Another possible symptom of cerebellar damage is bumpy and slurred speech, because the muscles needed for speech cannot be finely tuned in some cases of cerebellar damage.
