Spontaneous recruitment and annihilation of degrees of freedom in biological coordination

Abstract Whereas bifurcations within an already active set of components are well-known in biological coordination (e.g. gait transitions), less well understood is the process by which previously quiescent degrees of freedom are spontaneously activated. We introduce a simple paradigm to explore how complex, biological systems flexibly recruit and annihilate degrees of freedom according to parametric task requirements. A sequence of transitions within and across planes of motion is observed as a control parameter is varied. Such transitions are invariably preceded by enhancement of fluctuations in trajectory related variables. Our results suggest a theoretical model in which the main qualitative changes observed experimentally are a consequence of two consecutive Hopf bifurcations.