Shared dynamics of attentional cost and pattern stability.

This paper examines the informational activity devoted by the CNS to couple oscillating limbs in order to sustain and stabilize bimanual coordination patterns. Through a double-task paradigm associating a bimanual coordination task and a reaction time (RT) task, we investigated the relation between the stability of preferred bimanual coordination patterns and the central cost expended by the CNS for their stabilization. Ten participants performed in-phase and anti-phase coordination patterns in a dual task condition (coordination + RT) at several frequencies (0.5, 0.75, 1.0, 1.5, and 2.0 Hz), thereby decreasing the stability of the bimanual patterns. Results showed a U-shaped evolution of pattern stability and attentional cost, as a function of oscillation frequency, exhibiting a minimum value at the same frequency. These findings indicate that central cost and pattern stability covary and may share common, high order dynamics. Moreover, the attentional focus given to the bimanual coordination and the RT task was also manipulated by requiring either shared attention or priority to the coordination task. Such a manipulation led to a tradeoff between pattern stability and RT performance: The more stable the pattern, the more costly it is to stabilize. This suggests that stabilizing a coordination pattern incurs a central cost that depends on its intrinsic stability. Conceptual consequences of these results for understanding the relationship between attention and coordination are drawn, and the mechanisms putatively at work in dual tasks are discussed.