Somatosensory Realignment Following Single and Dual Force Field Adaptation

Abstract

Evidence that adaptive motor learning coincides with a realignment of somatosensory perception has led to hypotheses that a shared mechanism underlies both processes. This implies that these two phenomena should exhibit 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 canonical properties of adaptation in this paradigm. Our first experiment examined whether sensory realignment (for the perception of movement or static position) correlated with adaptation across individuals, and generalized beyond the trained reach direction. The results showed that force field adaptation coincided with a selective realignment of somatosensory perception of movement in the direction of the perturbing force, but this realignment 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. Overall, our results indicate that somatosensory realignment and adaptation exhibit different properties and are therefore unlikely to rely on the same underlying mechanism, although realignment does display some coherence with the nature of the perturbation. NEW AND NOTEWORTHYThis study is the first to demonstrate a dissociation in the realignment of somatosensory perceptions of static position and movement following adaptation to novel forces in the upper limb. By assessing whether perceptual realignment following force field adaptation exhibits two canonical properties of this type of motor learning - i.e., generalization to nearby movement directions and context dependence - this study constitutes a key test of theories positing a shared mechanism underlying the motor and perceptual processes.