- 著者
-
高草木 薫
- 出版者
- 日本脊髄外科学会
- 雑誌
- 脊髄外科 (ISSN:09146024)
- 巻号頁・発行日
- vol.27, no.3, pp.208-215, 2013 (Released:2017-05-11)
- 参考文献数
- 39
- 被引用文献数
-
1
This review discusses neuronal mechanisms controlling posture and locomotion. Volitional gait behaviors are composed of “automatic control of posture and rhythmic limb movements” that operate in conjunction with “intentional control of precise movements of the trunk, limbs, and feet.” The automatic control of posture and rhythmic limb movements is mediated by the ventromedial descending motor system from structures of the brainstem. Descending signals in this system activate spinal interneuronal circuits, which are termed central pattern generators (CPGs), to automatically generate a locomotor rhythm and pattern in cooperation with sensory afferents from muscles, joints, and skin. However, when moving, the subject requires intentional gait modification, which in turn critically involves an activation of the dorsolateral descending motor system, or the lateral corticospinal tract, arising from the motor cortical areas. An intentional gait control is always preceded by appropriate postural adjustments, which are themselves achieved by the motor programs in motor cortical areas including the supplementary motor area and premotor area. To generate and develop the motor programs, information of bodily function such as body schema, which is always updated at the temporoparietal cortex on the basis of proprioceptive, visual, vestibular and auditory sensations, can be critically required. The postural control program is propagated to the brainstem, via the cortico-reticular projection, so that anticipatory postural adjustment is performed by the activation of the ventromedial systems immediately before the onset of the intentional gait modification. Conversely, programs of intentional gait control are transmitted to the primary motor cortex so that precise limb trajectories can be generated and accurate foot placement is achieved by the activation of the corticospinal tract. Signals from the basal ganglia and the cerebellum regulate “automatic processes” by acting on the brainstem and “intentional processes” by acting on the cerebral cortex. Operation of the basal ganglia is largely affected by dopamine, and cerebellar function depends on feed-forward and feedback signals acting on the cerebellum. Dysfunction of either mechanism of the above processes may result in postural disturbance and/or gait failure. (328 words)