Distinct timing mechanisms produce discrete and continuous movements.
The differentiation of discrete and continuous movement is one of the pillars of motor behavior classification. Discrete movements have a definite beginning and end, whereas continuous movements do not have such discriminable end points. In the past decade there has been vigorous debate whether this classification implies different control processes. This debate up until the present has been empirically based. Here, we present an unambiguous non-empirical classification based on theorems in dynamical system theory that sets discrete and continuous movements apart. Through computational simulations of representative modes of each class and topological analysis of the flow in state space, we show that distinct control mechanisms underwrite discrete and fast rhythmic movements. In particular, we demonstrate that discrete movements require a time keeper while fast rhythmic movements do not. We validate our computational findings experimentally using a behavioral paradigm in which human participants performed finger flexion-extension movements at various movement paces and under different instructions. Our results demonstrate that the human motor system employs different timing control mechanisms (presumably via differential recruitment of neural subsystems) to accomplish varying behavioral functions such as speed constraints.
Huys
Raoul
R
Theoretical Neuroscience Group, UMR 6152 Institut des Sciences du Mouvement, CNRS and Université de Méditerranée, Marseille, France. raoul.huys@univmed.fr
Studenka
Breanna E
BE
Rheaume
Nicole L
NL
Zelaznik
Howard N
HN
Jirsa
Viktor K
VK
D000818:Animals; D003198:Computer Simulation; D006801:Humans; D008954:Models, Biological; D009048:Motor Skills / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D013647:Task Performance and Analysis; D013997:Time Factors