Evidence for an internal model dedicated to locomotor control

Abstract

We investigated the formation and transfer of internal models during locomotion and a visual motor pointing task performed with the leg using a novel backdrivable robot. Subjects adapted to a force field applied by a robot that pushed their leg upward during walking, and then immediately pointed with their lower shank to a small target in the same force field or with the field removed. This paradigm was designed to test whether the internal model formed during walking is available during pointing and vice versa. Subjects exhibited direct effects when pointing in the force field following walking in the same field suggesting that separate models are used in each task. The same was true for the reverse transition. This separate model paradigm was further supported by the presence of aftereffects when pointing with the field removed following a period of walking with the field removed. Evidence of aftereffects when the field was removed for both walking and pointing following adaptation to force fields in the other task indicates, however a partial sharing of internal models. The results provide evidence that the internal model formed during locomotion is largely dedicated to locomotion.