School of Psychology, Bangor University, Bangor, Wales, United Kingdom.
Bangor Imaging Unit, Bangor University, Bangor, Wales, United Kingdom.
J Neurophysiol. 2021 Apr 1;125(4):1251-1268. doi: 10.1152/jn.00645.2020. Epub 2021 Mar 3.
Humans can learn and produce skilled movement sequences from memory, yet the nature of sequence planning is not well understood. Previous computational and neurophysiological work suggests that movements in a sequence are planned as parallel graded activations and selected for output through competition. However, the relevance of this planning pattern to sequence production fluency and accuracy, as opposed to the temporal structure of sequences, is unclear. To resolve this question, we assessed the relative availability of constituent movements behaviorally during the preparation of motor sequences from memory. In three separate multisession experiments, healthy participants were trained to retrieve and produce four-element finger press sequences with particular timing according to an abstract sequence cue. We evaluated reaction time (RT) and error rate as markers of movement availability to constituent movement probes. Our results demonstrate that longer preparation time produces more pronounced differences in availability between adjacent sequence elements, whereas no effect was found for sequence speed or temporal grouping. Further, participants with larger position-dependent differences in movement availability tended to initiate correct sequences faster and with a higher temporal accuracy. Our results suggest that competitive preactivation is established gradually during sequence planning and predicts sequence skill, rather than the temporal structure of the motor sequence. Sequence planning is an integral part of motor sequence control. Here, we demonstrate that the competitive state of sequential movements during sequence planning can be read out behaviorally through movement probes. We show that position-dependent differences in movement availability during planning reflect sequence preparedness and skill but not the timing of the planned sequence. Behavioral access to the preparatory state of movements may serve as a marker of sequence planning capacity.
人类可以从记忆中学习和生成熟练的运动序列，但序列规划的本质仍不清楚。先前的计算和神经生理学研究表明，序列中的运动是作为并行分级激活进行规划的，并通过竞争选择输出。然而，这种规划模式与序列产生的流畅性和准确性相关，而与序列的时间结构无关，这一点尚不清楚。为了解决这个问题，我们在从记忆中准备运动序列时，从行为上评估了组成运动在各个方面的相对可用性。在三个独立的多会话实验中，健康参与者根据抽象的序列提示，接受了检索和生成具有特定时间结构的四元素手指按压序列的训练。我们评估了反应时间 (RT) 和错误率作为组成运动探针的运动可用性的指标。我们的结果表明，较长的准备时间会导致相邻序列元素之间的可用性差异更加明显，而序列速度或时间分组则没有影响。此外，运动可用性的位置依赖性差异较大的参与者往往更快地启动正确的序列，并且具有更高的时间准确性。我们的结果表明，竞争前激活是在序列规划过程中逐渐建立的，它可以预测序列技能，而不是运动序列的时间结构。序列规划是运动序列控制的一个组成部分。在这里，我们证明了在序列规划过程中顺序运动的竞争状态可以通过运动探针从行为上读取出来。我们表明，在规划过程中运动可用性的位置依赖性差异反映了序列准备和技能，但不反映计划序列的时间。对运动准备状态的行为访问可能是序列规划能力的一个标志。
