Graduate School of Education, The University of Tokyo, Tokyo, Japan.
Japan Society for the Promotion of Science, Tokyo, Japan.
Elife. 2024 Nov 27;13:RP96665. doi: 10.7554/eLife.96665.
The remarkable ability of the motor system to adapt to novel environments has traditionally been investigated using kinematically non-redundant tasks, such as planar reaching movements. This limitation prevents the study of how the motor system achieves adaptation by altering the movement patterns of our redundant body. To address this issue, we developed a redundant motor task in which participants reached for targets with the tip of a virtual stick held with both hands. Despite the redundancy of the task, participants consistently employed a stereotypical strategy of flexibly changing the tilt angle of the stick depending on the direction of tip movement. Thus, this baseline relationship between tip-movement direction and stick-tilt angle constrained both the physical and visual movement patterns of the redundant system. Our task allowed us to systematically investigate how the motor system implicitly changed both the tip-movement direction and the stick-tilt angle in response to imposed visual perturbations. Both types of perturbations, whether directly affecting the task (tip-movement direction) or not (stick-tilt angle around the tip), drove adaptation, and the patterns of implicit adaptation were guided by the baseline relationship. Consequently, tip-movement adaptation was associated with changes in stick-tilt angle, and intriguingly, even seemingly ignorable stick-tilt perturbations significantly influenced tip-movement adaptation, leading to tip-movement direction errors. These findings provide a new understanding that the baseline relationship plays a crucial role not only in how the motor system controls movement of the redundant system, but also in how it implicitly adapts to modify movement patterns.
运动系统适应新环境的非凡能力传统上是通过使用非冗余的运动任务来研究的，例如平面到达运动。这种局限性阻止了我们研究运动系统如何通过改变身体的冗余运动模式来实现适应。为了解决这个问题，我们开发了一种冗余的运动任务，参与者用双手握住虚拟棒的尖端来指向目标。尽管任务具有冗余性，但参与者始终采用一种灵活改变棒倾斜角度的典型策略，具体取决于尖端运动的方向。因此，尖端运动方向和棒倾斜角度之间的这种基本关系约束了冗余系统的物理和视觉运动模式。我们的任务使我们能够系统地研究运动系统如何在响应强制视觉干扰的情况下隐式地改变尖端运动方向和棒倾斜角度。这两种类型的干扰，无论是直接影响任务（尖端运动方向）还是不影响（尖端周围的棒倾斜角度），都能驱动适应，而隐式适应的模式则受到基本关系的指导。因此，尖端运动的适应与棒倾斜角度的变化相关，有趣的是，即使是看似可以忽略的棒倾斜干扰也会显著影响尖端运动的适应，导致尖端运动方向的错误。这些发现提供了一种新的理解，即基本关系不仅在运动系统如何控制冗余系统的运动方面起着至关重要的作用，而且在它如何隐式适应来修改运动模式方面也起着至关重要的作用。
