Visuomotor adaptation of locomotion and generalization across tasks investigated using virtual reality

Abstract

Sensorimotor recalibration in response to discrepant visual feedback occurs for goal-directed tasks like walking and pointing, and transfer across tasks can be used to infer the locus of adaptation. In this study, we distinguish two potential factors in transfer: the functional type of control task (locomotion vs. pointing) and the specific effectors that execute the actions (legs vs. arm). To distinguish functional and effector specificity, we created a hand locomotion task: subjects used pointing movements to simulate self-motion in virtual reality. Experiment 1 first tested whether adaptation of walking direction transferred to pointing, using a sinusoidal perturbation method (Hudson & Landy, 2012). Subjects walked toward a target in virtual reality and the mapping from physical to visual heading was varied over time. Interspersed with walking, subjects pointed toward targets without feedback to test transfer. Walking direction showed a damped and delayed response to the perturbations, but this adaptation did not transfer to pointing, consistent with previous studies using virtual reality. Experiment 2 tested transfer of adaptation from hand locomotion to pointing with hand locomotion performed either in textured ground with posts environment or target only environment. Experiment 3 tested transfer between hand locomotion and pointing using a similar method. Sinusoidal perturbations were applied to either the visual heading direction or the visual location of the hand, which produced adaptation, and transfer of adaptation across tasks was measured with interspersed test trials. When self-motion was controlled by a pointing movement rather than walking, there was partial transfer from locomotion to pointing, and from pointing to locomotion. Experiment 4 tested transfer of adaptation between hand locomotion and stepping, and similarity observed partial transfer in both directions. Even though the tasks involved different effectors, there was partial transfer between the two locomotion tasks. Our results demonstrate that visuomotor adaptation can generalize based on either shared functional task or shared effectors. This suggests that adaptation involves both functional and effector-specific components.