Somatosensory Realignment Following Single and Dual Force Field Adaptation

Evidence that adaptive motor learning coincides with a realignment of somatosensory perception has led to hypotheses that a shared mechanism underlies both processes, predicting similar properties. However, studies of somatosensory realignment with visuomotor adaptation have shown mixed support, possibly due to a confounding coactivation of sensory prediction errors and multisensory integration. While the former is thought to drive adaptation, both processes may contribute to somatosensory realignment. Here, we examined somatosensory realignment following force field adaptation, which is not confounded by multisensory integration. Across two experiments, we tested whether somatosensory realignment mimics three properties of adaptation in this paradigm. Our first experiment examined the specificity of somatosensory realignment to the perceptions of movement or static position and the generalization to reach directions adjacent to the one performed during the adaptation task. The results showed that force field adaptation coincided with a selective realignment of somatosensory perception of movement in the direction of the perturbing force that did not correlate with the magnitude of adaptation or generalize beyond the reach direction of the adaptation task. In a second experiment, we tested whether context-dependent dual adaptation to opposing force field perturbations coincides with a context-dependent dual realignment of somatosensory perception. The results showed no evidence of context-dependent somatosensory realignment after dual adaptation. Our results indicate that somatosensory realignment does not show the same properties as force field adaptation; however, it displays some coherence with the nature of the perturbation. Overall, our data suggest that somatosensory realignment and adaptation likely stem from distinct mechanisms.