Search

This review considers pathophysiological mechanisms of posture‐gait disturbances in Parkinson's disease (PD). Clinical studies have shown that posture‐gait disturbance attributes to the dysfunction of the whole neuraxis in addition to the musculoskeletal system. The cerebral cortex, basal ganglia (BG), cerebellum, brainstem, and spinal cord temporally and spatially integrate and coordinate multisensory feedback and efferent copies of the motor command. Therefore, the extensive repertoire of voluntary movements can be coupled with anticipatory and reactive postural adjustments to provide the framework for supporting and stabilizing the goal‐directed gait activity. Redundancies in the system allow adaptation and compensation through reward‐oriented and error‐based learning processes implemented through the BG and cerebellar pathways, respectively. However, the impairment of these systems in PD may considerably compromise the capacity to adapt and lead to maladaptive changes impairing posture‐gait control. When these impairments occur, the risk of falls can significantly increase, and interventions are required to reduce morbidity. The damage in dopamine (DA) neurons is the primary cause of PD. Insufficient DA supply in the striatum disturbs the operation of intrinsic networks in the BG. This also pathologically increases GABAergic BG output to the cerebral cortex and brainstem, resulting in functional disconnection of other structures from the BG. The disconnection makes PD patients disable to achieve habitually acquired automatized gait control. Moreover, Lewy body degeneration in most brain areas, particularly in cholinergic and other monoaminergic systems vulnerable to neurodegeneration, further disturbs posture‐gait control and alters non‐motor symptoms of PD. [ABSTRACT FROM AUTHOR]

An association is observed between the standing sway posture and falls in patients with stroke; hence, it is important to study their standing balance. Although there are studies on the standing balance in stroke patients, differences in control have not been adequately investigated. This study aims to propose a method to characterize the postural sway in standing stroke patients using a mathematical model. A musculoskeletal model and neural controller model were used to simulate ten stroke patients (five patients with cerebral hemorrhages and five patients with cerebral infarctions) and eight young healthy participants, and their data were monitored during quiet standing. The model parameters were adjusted by focusing on the maximum-minimum difference in sway, which was considered important in a previous study, and sway speed, which is frequently used in the analysis. The adjusted model parameters were subjected to dimension reduction using non-negative matrix factorization. Consequently, the sway characteristics of stroke patients were expressed as the magnitude of gain parameters related to the extension of the entire body. The results of this study demonstrated the possibility of representing the characteristics of postural sway as model parameters in stroke patients using a mathematical model. This characterization could lead to the design of individualized rehabilitation systems in the future. [ABSTRACT FROM AUTHOR]