The influence of augmented somatosensory feedback on visuomotor adaptation and inter-limb transfer


Healthy individuals can quickly adapt their movements when aiming in a virtual reality environment in which the visual representation of their hand is rotated relative to their actual hand motion. Specifically, individuals learn to compensate for the misaligned visual feedback by aiming to the left or right of the target, in the opposite direction of the rotation. These altered movements continue even when the rotated feedback is removed (i.e. individuals exhibit aftereffects). The purpose of the current study was to determine if augmented somatosensory feedback would be benefit motor learning in elderly participants and hence lead to greater aftereffects. Two groups of older adults (age range:40-75 years old ) aimed to targets when: 1) the cursor accurately indicated hand position, and 2) the cursor was rotated 30 degrees counter-clockwise from the actual hand position. One group of subjects received enhanced somatosensory feedback at the end of their reaching movements such that the robot handle they were holding vibrated with a frequency of 5 Hz for 1500 msec. Results showed that aftereffects were similar for both groups following reaches with the distorted visual feedback, with no significant influence of the augmented sensory feedback. Moreover, these changes in reaches transferred to the opposite (untrained) non-dominant hand, regardless of whether participants received enhanced sensory feedback or not. These findings suggest that the central nervous system ignores somatosensory information and relies more on visual feedback when adapting to altered visual feedback.