Neuroscience : Functional Neuroanatomy for Posture and Gait Control

By Kaoru Takakusaki

Abstract

Here we argue functional neuroanatomy for posture-gait control. Multi-sensory information such as somatosensory, visual and vestibular sensation act on various areas of the brain so that adaptable posture-gait control can be achieved. Automatic process of gait, which is steady-state stepping movements associating with postural reflexes including headeye coordination accompanied by appropriate alignment of body segments and optimal level of postural muscle tone, is mediated by the descending pathways from the brainstem to the spinal cord. Particularly, reticulospinal pathways arising from the lateral part of the mesopontine tegmentum and spinal locomotor network contribute to this process. On the other hand, walking in unfamiliar circumstance requires cognitive process of postural control, which depends on knowledges of self-body, such as body schema and body motion in space. The cognitive information is produced at the temporoparietal association cortex, and is fundamental to sustention of vertical posture and construction of motor programs. The programs in the motor cortical areas run to execute anticipatory postural adjustment that is optimal for achievement of goal-directed movements. The basal ganglia and cerebellum may affect both the automatic and cognitive processes of posturegait control through reciprocal connections with the brainstem and cerebral cortex, respectively. Consequently, impairments in cognitive function by damages in the cerebral cortex, basal ganglia and cerebellum may disturb posture-gait control, resulting in falling. 

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Figure 5. Hypotheses of cognitive process of posture-gait control. A: Cognition of bodily information. Sensory signals flowing into the central nervous system converge to the brainstem, cerebellum, thalamus, and cerebral cortex. At the level of cerebral cortex, signals from the visual cortex, vestibular cortex and primary sensory cortex (S1) is integrated and internal model of self-body, such as body schema and verticality can be constructed at the temporoparietal cortex including the vestibular cortex and posteroparietal cortex. Reciprocal connection between the temporoparietal cortex and cerebellum may contribute to this process. B: Transmission of the bodily information. The bodil y information is then transmitted to the supplementary motor area (SMA) and premotor area (PM) where the information can be utilized as materials to produce motor programs. Similarly, the information is transferred to hippocampus and is used to navigate further behaviors. C: Motor programming. The motor cortical areas closely cooperate with the basal ganglia and cerebellum so that appropriate motor programs are constructed. D: Postural control by corticofugal projections to the brainstem and spinal cord. The bodily information generated at the vestibular cortex may be utilized for sustention of vertical posture via cortico-vestibular and vestibulospinal tract. Signals from the prefrontal cortex including plans and intentions may trigger to run motor programs in the SMA/PM, which may include those for purposeful movements and associating postural control. The postural control program may be utilized to generate anticipatory postural adjustment via cortico-reticular and reticulospinal tract. Then motor programs are sent to the M1 so that goal-directed purposeful skilled movements can be achieved.

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