Mapping somatosensory vs. visual targets for the online control of the unseen limb


When performing goal-directed upper-limb reaches to a visual target, the sensorimotor system can adjust the ongoing movement to changes in target location, even without vision of the reaching limb. These limb trajectory amendments may be based on visual information about the new target location and online somatosensory inputs from the unseen hand processed in a visual reference frame. The purpose of the present study was to determine if the sensorimotor transformations used for the online control of unseen hand movements to somatosensory targets occurs in a visual or a non-visual reference frame. Reaches were made towards a somatosensory or a visual targets that either remained stable, or changed position: before movement onset (~450 ms), or 100 ms or 200 ms after. In response to both the 100 ms and 200 ms perturbations, participants exhibited shorter correction latencies, larger correction amplitudes, and smaller endpoint errors, when reaching to somatosensory targets compared to when reaching to visual targets. These results indicate that, for the online control of somatosensory target perturbations, hand position was unlikely transformed into visual reference frame prior to the initiation of corrections.

Acknowledgments: Natural Sciences and Engineering Research Council of Canada (NSERC), Canada Foundation for Innovation (CFI), Ontario Research Fund (ORF), University of Toronto