Department of Health and Kinesiology, Texas A&M University, College Station, TX 77843-4243, USA.
Exp Brain Res. 2013 Aug;229(1):47-60. doi: 10.1007/s00221-013-3589-y. Epub 2013 Jun 13.
Across three different task conditions, the adaptability of reciprocal aiming movements was investigated. Task difficulty was manipulated by changing ID, with 9 IDs between 2.5 and 6.5 tested. Reciprocal aiming movements were performed with ID scaled (predictable) in a trial in a decreasing (high 6.5-low 2.5) or increasing manner (low 2.5-high 6.5) or with ID constant in a trial and changed randomly across trials. Movement time scaled linearly with ID in both the scaling ID and control ID presentations. A critical ID boundary (IDC) was identified, and the adaptation of aiming movements was a function of this critical boundary. For IDs < IDC, the results are interpreted as representing a predominance for pre-planned control based on a dwell time measure and a symmetry ratio measure (time spent accelerating-decelerating the limb). Within this ID range, movement harmonicity was changed to a greater extent when ID was scaled in a predictable direction as compared to being presented in a random manner. For IDs > IDC, the findings suggest a predominance for feedback control based on the dwell time and symmetry ratio measure. Within this ID range, the absolute time spent decelerating was increased, possibly to insure accuracy and minimize MT, with the predictable changes associated with an increase in ID needing less time devoted to feedback processing compared to the other ID presentations. The results are consistent with the theoretical position that aiming motions may be controlled by a limit cycle mechanism with ID < IDC, while aiming motions may be controlled by a fixed-point mechanism with ID > IDC. The results suggest that the ability of the motor system to adapt to both scaled and random changes in ID revolves around a modulation of pre-planned and feedback-based control processes.
在三种不同的任务条件下，研究了相互瞄准运动的适应性。通过改变 ID 来操纵任务难度，测试了 9 个在 2.5 到 6.5 之间的 ID。在一个试验中，通过按比例缩放（可预测）ID（从高 6.5 到低 2.5 或从低 2.5 到高 6.5）或在一个试验中保持 ID 不变但在试验中随机改变来进行相互瞄准运动。在缩放 ID 和对照 ID 呈现中，运动时间都与 ID 呈线性缩放。确定了一个关键 ID 边界（IDC），瞄准运动的适应是该关键边界的函数。对于 ID < IDC 的情况，结果被解释为代表基于停留时间测量和对称比测量（花费在加速-减速肢体上的时间）的预规划控制占主导地位。在这个 ID 范围内，当 ID 按可预测的方向缩放时，与以随机方式呈现相比，运动谐波性发生了更大的变化。对于 ID > IDC 的情况，研究结果表明基于停留时间和对称比测量，反馈控制占主导地位。在这个 ID 范围内，减速所花费的绝对时间增加，可能是为了确保准确性并最小化 MT，可预测的 ID 变化与反馈处理相比需要更少的时间，与其他 ID 呈现相比。这些结果与理论立场一致，即瞄准运动可能由 ID < IDC 下的极限环机制控制，而瞄准运动可能由 ID > IDC 下的固定点机制控制。结果表明，运动系统适应 ID 的缩放和随机变化的能力围绕着对预规划和基于反馈的控制过程的调节。
