Balancing objects on the feet — An fMRI experiment using the MR-compatible stepper MARCOS

Little is known about the neural correlates underlying the control of highly coordinated bilateral lower limb movements. In this paper we present an fMRI paradigm consisting of balancing a virtual ball rolling on a virtual bar. The subject can control the position of the bar by its lower limbs using the MR-compatible stepper MARCOS. Concurrent visual and force feedback about the state of the physical model of ball and bar is presented to the subject during task execution. In a pilot study, significant cerebellar and parieto-frontal activity was found, according to physiological expectations, demonstrating the feasibility of the experimental set-up. Further experiments will help to better understand human motor control as well as to develop more targeted rehabilitation strategies for patients with neurological movement disorders of the lower limbs.