Shoja Otella, Towhidkhah Farzad, Hassanlouei Hamidollah, Levin Mindy F, Bahramian Alireza, Nadeau Sylvie, Zhang Lei, Feldman Anatol G
Department of Neuroscience, University of Montreal, Montreal, QC, Canada.
Department of Biomedical Engineering, Amirkabir University of Technology, Tehran, Iran.
Exp Brain Res. 2023 May;241(5):1353-1365. doi: 10.1007/s00221-023-06593-x. Epub 2023 Apr 3.
Human locomotion may result from monotonic shifts in the referent position, R, of the body in the environment. R is also the spatial threshold at which muscles can be quiescent but are activated depending on the deflection of the current body configuration Q from R. Shifts in R are presumably accomplished with the participation of proprioceptive and visual feedback and responsible for transferring stable body balance (equilibrium) from one place in the environment to another, resulting in rhythmic activity of multiple muscles by a central pattern generator (CPG). We tested predictions of this two-level control scheme. In particular, in response to a transient block of vision during locomotion, the system can temporarily slow shifts in R. As a result, the phase of rhythmical movements of all four limbs will be changed for some time, even though the rhythm and other characteristics of locomotion will be fully restored after perturbation, a phenomenon called long-lasting phase resetting. Another prediction of the control scheme is that the activity of multiple muscles of each leg can be minimized reciprocally at specific phases of the gait cycle both in the presence and absence of vision. Speed of locomotion is related to the rate of shifts in the referent body position in the environment. Results confirmed that human locomotion is likely guided by feedforward shifts in the referent body location, with subsequent changes in the activity of multiple muscles by the CPG. Neural structures responsible for shifts in the referent body configuration causing locomotion are suggested.
人体运动可能源于身体在环境中的参考位置R的单调变化。R也是一个空间阈值，在该阈值下肌肉可以保持静止，但会根据当前身体构型Q相对于R的偏移而被激活。R的变化大概是在本体感觉和视觉反馈的参与下完成的，并负责将稳定的身体平衡（平衡状态）从环境中的一个位置转移到另一个位置，从而通过中枢模式发生器（CPG）产生多块肌肉的节律性活动。我们测试了这种两级控制方案的预测。特别是，在运动过程中对视觉的短暂阻断做出反应时，系统可以暂时减缓R的变化。结果，即使在扰动后运动的节律和其他特征将完全恢复，所有四肢的节律性运动的相位也会在一段时间内发生变化，这种现象称为持久相位重置。该控制方案的另一个预测是，无论是否有视觉，每条腿的多块肌肉的活动在步态周期的特定阶段都可以相互最小化。运动速度与身体在环境中的参考位置的变化率有关。结果证实，人体运动可能由参考身体位置的前馈变化引导，随后CPG会改变多块肌肉的活动。文中还提出了负责导致运动的参考身体构型变化的神经结构。
