Visual information interacts with neuromuscular factors in the coordination of bimanual isometric force.

The role of perceptual-motor processes in the coordination and control of movement is a long standing issue. Nevertheless, there is no coherence on theoretical perspectives with their being frameworks that emphasize perceptual, motor and perceptual-motor processes in coordination and control. The purpose of this study was to examine the interactive effects of visual information and factors of neuromuscular organization (force level, force direction, and homologous muscle pairs) on coordination patterns in bimanual isometric force production. In Experiment 1, the participants were required to abduct two index fingers isometrically and produce simultaneous forces such that their sum matched the constant force target specified at two force levels (10 and 40% of maximum voluntary contraction (MVC)). Visual information of the force outputs was either present or absent between conditions. The results showed that the coordination patterns interact with visual feedback in that the two finger forces exhibit negative correlation with vision and positive correlation without vision, with stronger correlation in each case found at higher force levels. In Experiment 2, the force direction and muscles involved in the task were different between the hands. In comparison with Experiment 1, the negative correlation was stronger with vision at 40% MVC (but equal at 10% MVC), and positive correlation was weaker without vision at 10% MVC (but equal at 40% MVC). The findings provide further evidence that the coordination patterns in bimanual isometric force production are specified by the interaction of task-relevant visual information and force level and, to a lesser degree by force direction and the muscles involved in the task. The capacity to exploit information mediates coordination and control, and the effective utilization of information is dependent on the specific action.