Cerebellar Control of Posture

Abstract

Cerebellar control of posture is mainly based on the connections of the cerebellum with brainstem reticular formation and vestibular system, which are the source of the medial descending system providing the control of the body, i.e., posture and balance. The story of studying the role of cerebellum in postural control started from the works of Rolando, Flourens, Magendie, and especially Luciani who pointed out the role of the cerebellum in control of postural tone and muscle force. He described the main results of cerebellar lesions: atonia, asthenia, astasia, and dysmetria. The studies were continued by Lewandowsky, Thomas, Babinski, Bekhterev, Sherrington and, in twentieth century, by Dow and Moruzzi, Ito, Diener, Dichgans, and others. Postural disturbances after cerebellar lesions are described both in animals and in patients. Particularly, MRI data were very efficient to provide correlations between lesions of a definite area of the cerebellum and disturbances of posture and locomotion. The fMRI studies of human locomotor centers revealed the activation including pacemakers for gait initiation and speed regulation in the interfastigial cerebellum and bilateral midbrain tegmentum (cerebellar and mesencephalic locomotor regions), their descending target regions in the pontine reticular formation, and the rhythm generators in the cerebellar vermis and paravermal cortex. A genetic approach is actively used for studying cerebellar control of posture. Specific genes expressed in cerebellum encoding glutamate receptors and other molecules were shown to affect postural control in mice. Plasticity in cerebellum (synaptogenesis, increasing dendritic trees) was described after complicated motor training. The role of cerebellum in learning was studied by Brindley, Marr, Albus, Thach, Ito, and others. The role of the cerebellum in the reorganization of posture and in learning new postural tasks in animals and humans has also been investigated. Though other brain systems such as the basal ganglia and the motor cortex-pyramidal system are specifically involved in this process as well, the cerebellum seems to be one of the main structures providing learning of voluntary control of posture. The cerebellar mechanisms of feedback learning could be a basis of this process. In particular, the motor cortex might be involved in feedback control whereas the cerebellum might play a role in feedforward control by acquiring inverse models in new postural tasks.