Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan
Faculty of Environment and Information Studies, Keio University, Kanagawa 252-0882, Japan.
J Exp Biol. 2018 Aug 23;221(Pt 16):jeb179457. doi: 10.1242/jeb.179457.
The capacity for auditory-motor coordination (AMC) is shared by several species, among which humans are most flexible in coordinating with tempo changes. We investigated how humans lose this tempo flexibility at their upper rate limit, and the effect of skill level on this phenomenon. Seven skilled street dancers, including a world champion, and 10 non-dancers were instructed to bend their knees according to a metronome beat in a standing position at eight constant beat frequencies (3.8-5 Hz). Although maximum frequency of movement during the task was 4.8 Hz in the non-dancers and 5.0 Hz in the dancers, the rate limit for AMC was 4.1 Hz in the non-dancers and 4.9 Hz in the dancers. These results suggest that the loss of AMC was not due to rate limit of movement execution but rather to a constraint on the AMC process. In addition, mediation analysis revealed that a kinematic bias (i.e. the extent of knee flexion during the task) causally affected the extent of phase wandering via mediating factors (e.g. the extent to which movement frequency was reduced relative to the beat frequency). These results add evidence that gravity acts as constraint on AMC involving vertical rhythmic movement.
听觉-运动协调能力（AMC）在多个物种中共享，其中人类在与节奏变化协调方面最为灵活。我们研究了人类在其上限速度下如何失去这种节奏灵活性，以及技能水平对这种现象的影响。七名专业的街头舞者，包括一位世界冠军，和 10 名非舞者被要求在站立姿势下根据节拍器的节拍弯曲膝盖，节拍频率为八个恒定频率（3.8-5 Hz）。尽管非舞者在任务中的最大运动频率为 4.8 Hz，而舞者为 5.0 Hz，但 AMC 的速率限制在非舞者中为 4.1 Hz，在舞者中为 4.9 Hz。这些结果表明，AMC 的丧失不是由于运动执行的速率限制，而是由于 AMC 过程的限制。此外，中介分析表明，运动学偏差（即任务期间的膝关节弯曲程度）通过中介因素（例如运动频率相对于节拍频率降低的程度）因果关系地影响相位漂移的程度。这些结果进一步证明了重力对涉及垂直节奏运动的 AMC 起着约束作用。
