What happens when cerebrum and cerebellum are surgically separated (or partially separated)?
Is this lethal, and if not, what are consequences for brain operations?
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Q: What happens when cerebrum and cerebellum are surgically separated (or partially separated)?
A: If that happens, the functional connection between the cerebrum and cerebellum will be destroyed. Now, the connection between the cerebrum and cerebellum serves to do these functions (1,2):
Coordination of voluntary movements. Most movements are composed of a number of different muscle groups acting together in a temporally coordinated fashion. One major function of the cerebellum is to coordinate the timing and force of these different muscle groups to produce fluid limb or body movements.
Motor learning. The cerebellum is important for motor learning. The cerebellum plays a major role in adapting and fine-tuning motor programs to make accurate movements through a trial-and-error process (e.g., learning to hit a baseball).
Cognitive functions. Although the cerebellum is most understood in terms of its contributions to motor control, it is also involved in certain cognitive functions, such as language. Thus, like the basal ganglia, the cerebellum is historically considered as part of the motor system, but its functions extend beyond motor control in ways that are not yet well understood.” (1)
If the connection is severed, these functions will be impaired, resulting in loss of coordination of motor movement (such as dysmetria, dysdiadokokinesia, and stuttering speech), loss of motor learning (it will be very difficult to learn new motor skills, be it sports, musical performance, dancing, etc.), and impairment of some cognitive functions (e.g., impaired spatial cognition, dysprosody, anomia, executive dysfunction with difficulties in planning, set-shifting, abstraction, working memory, and verbal fluency, personality change, and inappropriate behavior ).
Q: Is this lethal, and if not, what are consequences for brain operations?
A: A separation of the cerebrum and cerebellum will not be lethal. Medically, there is no diseases or conditions that require a separation between the two structures. But there are diseases that, in effects, separate the two structures, such as stroke, tumor, or demyelinating disease that affects the superior cerebellar peduncles (which connects the cerebrum and cerebellum). Or there may be diseases/conditions that destroy the cerebellum, such as stroke, tumor, trauma, or operation that removes the cerebellum to treat these diseases/conditions, and thus having the same effects of separating the cerebellum from the cerebrum. All these pathological conditions and operations that treat them can causes the symptoms and signs mentioned above, but none are lethal by themselves (i.e., none are lethal if there are no other complications).
James Knierim. Chapter 5. Cerebellum: 5.1 Overview: Functions of the Cerebellum Neuroscience Online. The University of Texas. Health Science Center at Houston. McGovern Medical School.
William C Hall. Chapter 18. Modulation of Movement by the Cerebellum. In: Purves D, Augustine GJ, David Fitzpatrick D, Hall WC, Lamantia AS, McNamara JO, Williams SM, editors. Neuroscience. 3rd ed. Sunderland, Massachusetts: Sinauer Associates Inc; 2004. ISBN-13: 9780878937257 ISBN-10: 0878937250.
Mark Rapoport. The Role of the Cerebellum in Cognition and Behavior. A Selective Review. The Journal of Neuropsychiatry and Clinical Neurosciences.