Department of Kinesiology, The Pennsylvania State University, Rec.Hall-268N, University Park, PA, 16802, USA.
Department of Health and Kinesiology, Purdue University, West Lafayette, IN, 47907, USA.
Exp Brain Res. 2024 Sep;242(9):2177-2191. doi: 10.1007/s00221-024-06892-x. Epub 2024 Jul 11.
We explored two types of anticipatory synergy adjustments (ASA) during accurate four-finger total force production task. The first type is a change in the index of force-stabilizing synergy during a steady state when a person is expecting a signal to produce a quick force change, which is seen even when the signal does not come (steady-state ASA). The other type is the drop in in the synergy index prior to a planned force change starting at a known time (transient ASA). The subjects performed a task of steady force production at 10% of maximal voluntary contraction (MVC) followed by a ramp to 20% MVC over 1 s, 3 s, and as a step function (0 s). In another task, in 50% of the trials during the steady-state phase, an unexpected signal could come requiring a quick force pulse to 20% MVC (0-surprise). Inter-trial variance in the finger force space was used to quantify the index of force-stabilizing synergy within the uncontrolled manifold hypothesis. We observed significantly lower synergy index values during the steady state in the 0-ramp trials compared to the 1-ramp and 3-ramp trials. There was also larger transient ASA during the 0-ramp trials. In the 0-surprise condition, the synergy index was significantly higher compared to the 0-ramp condition whereas the transient ASA was significantly larger. The finding of transient ASA scaling is of importance for clinical studies, which commonly involve populations with slower actions, which can by itself be associated with smaller ASAs. The participants varied the sharing pattern of total force across the fingers more in the task with "surprises". This was coupled to more attention to precision of performance, i.e., inter-trial deviations from the target as reflected in smaller variance affecting total force, possibly reflecting higher concentration on the task, which the participants perceived as more challenging compared to a similar task without surprise targets.
我们探索了两种类型的预期协同调整（ASA）在准确的四指总力产生任务期间。第一种是在一个人期望信号产生快速力变化时，力稳定协同作用的指数发生变化，即使信号没有到来（稳态 ASA）也是如此。另一种是在计划的力变化开始之前，协同作用指数下降，已知时间（瞬态 ASA）。受试者以 10%的最大自主收缩（MVC）进行稳定力产生任务，然后在 1 秒、3 秒和作为阶跃函数（0 秒）上升到 20%MVC。在另一个任务中，在稳态阶段的 50%的试验中，可能会出现意外信号，需要快速将力脉冲提高到 20%MVC（0 意外）。在无控流形假设中，手指力空间的试验间方差用于量化力稳定协同作用的指数。我们观察到，在 0 斜坡试验中，与 1 斜坡和 3 斜坡试验相比，稳态时的协同作用指数值显著降低。在 0 斜坡试验中也有较大的瞬态 ASA。在 0 意外条件下，协同作用指数明显高于 0 斜坡条件，而瞬态 ASA 明显较大。瞬态 ASA 标度的发现对临床研究很重要，临床研究通常涉及动作较慢的人群，这本身可能与较小的 ASA 有关。在有“惊喜”的任务中，参与者在总力在手指间的分配模式上变化更大。这与对性能精度的关注有关，即从目标的试验间偏差，反映在较小的方差影响总力，可能反映出更高的注意力集中在任务上，参与者认为与没有惊喜目标的类似任务相比，该任务更具挑战性。
