Toussaint H M, Michies Y M, Faber M N, Commissaris D A, van Dieën J H
Amsterdam Spine Unit, Institute for Fundamental and Clinical Human Movement Sciences, Faculty of Human Movement Sciences, The Netherlands.
Exp Brain Res. 1998 May;120(1):85-94. doi: 10.1007/s002210050380.
Anticipatory control of motor output enables fast and fluent execution of movement. This applies also to motor tasks in which the performance of movement brings about a disturbance to balance that is not completely predictable. For example, in bi-manual lifting the pick-up of a load causes a forward shift of the centre of mass with consequent disturbance of posture. Anticipatory postural adjustments are scaled to the expected magnitude of the perturbation and are initiated well before the availability of sensory information characterising the full nature of the postural disturbance. However, when the postural disturbance unexpectedly changes, the anticipatory adjustment of joint torques is not equilibrated and may result in a disturbance to balance. In a previous study, it was demonstrated that apart from anticipatory postural adjustments, corrective responses after load pick-up are used to further compensate the postural disturbance. In this study it was examined whether the central nervous system (CNS) assembles a strategy that incorporates both anticipatory control and corrective responses, in which the magnitude of the anticipatory postural adjustments depends on the perceived level of predictability of the postural disturbance. Subjects performed series of lifts in which the magnitude of the load was never revealed to the subject. Two boxes equal in size and colour, but different in mass (6 and 16 kg), were used. Differences in expectation were created by several lifts with the 16-kg load before the 6-kg box was presented. It was observed that the number of strong corrective responses (stepping) varied with the number of 16-kg trials that formed the prior experience when the final 6-kg trial was presented. The follow-up question was whether control relied more on anticipation in the stepping trials, compared with trials in which such gross signs of imbalance were absent. In this study it was shown that subjects when stepping (i) exhibited differential anticipatory postural adjustments in comparison with 6-kg trials in which expectation was not shaped by preceding 16-kg trials, and (ii) scaled the anticipatory postural adjustments similar to those preceding lift-off of the 16-kg trial preceding it. These findings emphasise the programmed nature of the anticipatory postural adjustments and the ability of the CNS to selectively tune the anticipatory postural adjustments to stored information gained during the previous lift(s).
对运动输出的预期控制能够实现快速流畅的动作执行。这同样适用于那些运动表现会对平衡造成不完全可预测干扰的运动任务。例如，在双手提举时，拿起重物会导致重心向前移动，进而干扰姿势。预期姿势调整会根据预期的扰动大小进行缩放，并在表征姿势干扰全部性质的感觉信息可用之前就提前启动。然而，当姿势干扰意外变化时，关节扭矩的预期调整无法达到平衡，可能会导致平衡受到干扰。在先前的一项研究中，已证明除了预期姿势调整外，拿起重物后的纠正反应也用于进一步补偿姿势干扰。在本研究中，研究了中枢神经系统（CNS）是否会构建一种结合预期控制和纠正反应的策略，其中预期姿势调整的大小取决于所感知的姿势干扰的可预测水平。受试者进行了一系列提举，其中重物的大小从未向受试者透露。使用了两个大小和颜色相同但质量不同（6千克和16千克）的箱子。在展示6千克箱子之前，先进行几次16千克重物的提举，从而产生预期差异。观察到，当呈现最后一次6千克的试验时，强烈纠正反应（迈步）的次数会随着构成先前经验的16千克试验次数而变化。后续问题是，与没有这种明显失衡迹象的试验相比，在迈步试验中控制是否更多地依赖预期。本研究表明，受试者在迈步时：（i）与6千克试验（其中预期未受先前16千克试验影响）相比，表现出不同的预期姿势调整；（ii）预期姿势调整的缩放与之前16千克试验提举前的调整类似。这些发现强调了预期姿势调整的程序性本质，以及中枢神经系统根据先前提举过程中获得的存储信息选择性调整预期姿势调整的能力。
