1 Mathematisches Institut, Universität Koblenz, Koblenz, Germany. Electronic address: rrockenfeller@uni-koblenz.de.
2 Biomechanics and Biorobotics, Stuttgart Center for Simulation Sciences (SC SimTech), Universität Stuttgart, Stuttgart, Germany; Friedrich-Schiller-Universität, Jena, Germany.
3 Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, Ohio.