The purpose of this study was to investigate central nervous system (CNS) strategies for controlling multifinger forces during a circle-drawing task. Subjects drew 30 concentric, discontinuous clockwise and counter clockwise circles, at self and experimenter-set paces. The three-dimensional trajectory of the pen’s center of mass and the three-dimensional forces and moments of force at each contact between the hand and the pen were recorded. Uncontrolled Manifold Analysis was used to quantify the synergies between pen-hand contact forces in radial, tangential and vertical directions. Results showed that synergies in the radial and tangential components were significantly stronger than in the vertical component. Synergies in the clockwise direction were significantly stronger than the counterclockwise direction in the radial and vertical components. Pace was found to be insignificant under any condition.
Hooke, Karol, Park, and Shim are with the Department of Kinesiology, University of Maryland, College Park, MD. Kim and Shim are with the Department of Mechanical Engineering, Kyung Hee University, Global Campus, Korea. Shim is also with the Neuroscience and Cognitive Science Graduate Program, and the Fischell Department of Bioengineering, University of Maryland, College Park, MD.