Force field training to facilitate learning visual distortions: a "sensory crossover" experiment

Previous studies on reaching movements have shown that people can adapt to distortions that are either visuomotor (e.g., prism glasses) or mechanical (e.g., force fields) through repetitive training. Other work has shown that these two types of adaptation may share similar neural resources. One effective test of this sharing hypothesis would be to show that one could teach one using the other. This study investigated whether training with a specialized force field could benefit the learning of a visual distortion. Two groups of subjects volunteered to participate in this study. One group of subjects trained directly on a visual rotation. The other group of subjects trained in a "mixed field" condition. The mixed field was primarily a force field that was specially designed so that, after adapting to its characteristics, the subject would make the appropriate movement in the visual rotation condition. The mixed field condition also contained intermittent test movements that evaluated performance in the visual rotation condition. Results showed that errors reduced more rapidly in the mixed field condition. We also found that subjects were able to generalize what they learned to movement directions that were not part of the training, but there was no detectable difference between the two groups. Finally, we found no difference in the rate these training effects washed out after subjects returned to normal conditions. This study shows that training with robotic forces can facilitate the learning of visual rotations. The learning may be enhanced in the mixed condition by the addition of cutaneous and proprioceptive force sensors. Moreover, this study can be applied to telerobotics and the rehabilitation of brain injured individuals, where there is often a distortion in hand-eye coordination.