Neuromotor Control Laboratory, Department of Biomedical Engineering, Marquette University and Medical College of Wisconsin, Engineering Hall, Rm 342, P.O. Box 1881, Milwaukee, WI, 53201-1881, USA.
Marquette University, Milwaukee, WI, 53233, USA.
Exp Brain Res. 2023 Sep;241(9):2209-2227. doi: 10.1007/s00221-023-06664-z. Epub 2023 Jul 28.
We examined the extent to which intentionally underperforming a goal-directed reaching task impacts how memories of recent performance contribute to sensorimotor adaptation. Healthy human subjects performed computerized cognition testing and an assessment of sensorimotor adaptation, wherein they grasped the handle of a horizontal planar robot while making goal-directed out-and-back reaching movements. The robot exerted forces that resisted hand motion with a spring-like load that changed unpredictably between movements. The robotic test assessed how implicit and explicit memories of sensorimotor performance contribute to the compensation for the unpredictable changes in the hand-held load. After each movement, subjects were to recall and report how far the hand moved on the previous trial (peak extent of the out-and-back movement). Subjects performed the tests under two counter-balanced conditions: one where they performed with their best effort, and one where they intentionally sabotaged (i.e., suppressed) kinematic performance. Results from the computerized cognition tests confirmed that subjects understood and complied with task instructions. When suppressing performance during the robotic assessment, subjects demonstrated marked changes in reach precision, time to capture the target, and reaction time. We fit a set of limited memory models to the data to identify how subjects used implicit and explicit memories of recent performance to compensate for the changing loads. In both sessions, subjects used implicit, but not explicit, memories from the most recent trial to adapt reaches to unpredictable spring-like loads. Subjects did not "give up" on large errors, nor did they discount small errors deemed "good enough". Although subjects clearly suppressed kinematic performance (response timing, movement variability, and self-reporting of reach error), the relative contributions of sensorimotor memories to trial-by-trial variations in task performance did not differ significantly between the two testing conditions. We conclude that intentional performance suppression had minimal impact on how implicit sensorimotor memories contribute to adaptation of unpredictable mechanical loads applied to the hand.
我们研究了在目标导向的伸手任务中表现不佳的程度会如何影响最近的表现记忆对感觉运动适应的贡献。健康的人类受试者进行了计算机认知测试和感觉运动适应评估，在评估中，他们握住水平平面机器人的手柄，进行目标导向的内外往返伸手运动。机器人施加的力与弹簧负载抵抗手部运动，负载在运动之间不可预测地变化。机器人测试评估了感觉运动表现的内隐和外显记忆如何有助于补偿手持负载的不可预测变化。在每次运动后，受试者需要回忆并报告前一次试验中手移动的距离（内外往返运动的峰值幅度）。受试者在两种平衡条件下进行测试：一种是尽最大努力完成任务，另一种是故意破坏（即抑制）运动表现。计算机认知测试的结果证实了受试者理解并遵守了任务指令。在机器人评估过程中抑制表现时，受试者在伸手精度、到达目标的时间和反应时间方面表现出明显的变化。我们拟合了一组有限记忆模型来分析数据，以确定受试者如何利用最近的表现的内隐和外显记忆来适应不断变化的负载。在两个会话中，受试者都使用最近试验的内隐记忆，但不使用外显记忆，来适应不可预测的弹簧样负载。受试者没有“放弃”大错误，也没有低估被认为“足够好”的小错误。尽管受试者明显抑制了运动表现（响应时间、运动变异性和伸手错误的自我报告），但在两个测试条件下，感觉运动记忆对任务表现的逐次变化的相对贡献并没有显著差异。我们得出结论，故意的表现抑制对感觉运动内隐记忆如何有助于适应施加到手部的不可预测机械负载的影响很小。
