First results on the role of cutaneous feedback during the learning of a force field in reaching tasks

According to International Labour Organization (ILO), more than two million people die or loose the working capability every year because of accidents or work-related diseases. The insufficient degree of interaction between human and machine (HMI) is one of the major causes. Developments in HMI have been achieved in several fields of robotics research. However, the translational relevance of such innovations is often underestimated. To date, several findings have generated some preliminary indications about the way to facilitate learning of motor tasks with the assistance of robotic devices. This general goal, initially raised by the community of rehabilitation robotics researchers, is also extendable to different application fields since faster learning of a task by the user means more productivity and safety. Haptic stimulation can help humans learn perceptual motor skills, but the precise way in which it influences the learning process has not yet been clarified. This study investigates the role of the kinesthetic and cutaneous components of haptic feedback during the learning of a viscous curl field, taking also into account the influence of visual feedback. Results indicate that kinesthetic stimuli played a primary role during motor adaptation to the viscous field, which is a fundamental premise to motor learning and rehabilitation. On the other hand, cutaneous stimulation alone appeared not to bring significant direct or adaptation effects, although it needs further investigations. The experimental conditions with visual cancellation of position error seems to show slower adaptation rates, indicating that visual feedback actively helps to the formation of internal models. However, modest learning effects were shown when the visual information was used to substitute the viscous field.