Reschechtko Sasha, Hasanbarani Fariba, Akulin Vladimir M, Latash Mark L
Pennsylvania State University, University Park, PA 16802, USA.
Pennsylvania State University, University Park, PA 16802, USA; University of Tehran, Tehran, Iran.
Neuroscience. 2017 May 14;350:94-109. doi: 10.1016/j.neuroscience.2017.03.022. Epub 2017 Mar 24.
The study explored unintentional force changes elicited by removing visual feedback during cyclical, two-finger isometric force production tasks. Subjects performed two types of tasks at 1Hz, paced by an auditory metronome. One - Force task - required cyclical changes in total force while maintaining the sharing, defined as relative contribution of a finger to total force. The other task - Share task - required cyclical changes in sharing while keeping total force unchanged. Each trial started under full visual feedback on both force and sharing; subsequently, feedback on the variable that was instructed to stay constant was frozen, and finally feedback on the other variable was also removed. In both tasks, turning off visual feedback on total force elicited a drop in the mid-point of the force cycle and an increase in the peak-to-peak force amplitude. Turning off visual feedback on sharing led to a drift of mean share toward 50:50 across both tasks. Without visual feedback there was consistent deviation of the two force time series from the in-phase pattern (typical of the Force task) and from the out-of-phase pattern (typical of the Share task). This finding is in contrast to most earlier studies that demonstrated only two stable patterns, in-phase and out-of-phase. We interpret the results as consequences of drifts of parameters in a dynamical system leading in particular to drifts in the referent finger coordinates toward their actual coordinates. The relative phase desynchronization is caused by the right-left differences in the hypothesized drift processes, consistent with the dynamic dominance hypothesis.
该研究探讨了在周期性的双指等长力产生任务中去除视觉反馈所引发的无意用力变化。受试者以1Hz的频率执行两种类型的任务，由听觉节拍器同步。一种任务——力任务——要求总力进行周期性变化，同时保持分配比例，即手指对总力的相对贡献。另一种任务——分配任务——要求分配比例进行周期性变化，同时保持总力不变。每次试验开始时，力和分配比例都有完整的视觉反馈；随后，被指示保持恒定的变量的反馈被冻结，最后另一个变量的反馈也被去除。在这两种任务中，关闭总力的视觉反馈会导致力周期中点下降，峰峰值力幅度增加。关闭分配比例的视觉反馈会导致两种任务中的平均分配比例都向50:50漂移。没有视觉反馈时，两个力时间序列与同相模式（力任务的典型模式）和异相模式（分配任务的典型模式）均存在持续偏差。这一发现与大多数早期研究不同，早期研究仅表明存在同相和异相两种稳定模式。我们将这些结果解释为动态系统中参数漂移的结果，特别是导致参考手指坐标向其实际坐标漂移。相对相位去同步是由假设的漂移过程中的左右差异引起的，这与动态优势假说一致。
