A hypothetical explanatory sensorimotor model of bilateral limb interference.

Goal-directed movements of a limb are optimized by sensorimotor integration, a process that merges both sensory and motor representations. In a previous study, we revealed that abnormal sensory representation can impair reach-to-grasp movements in patients with spinothalamocortical pathway lesions. This abnormal motor control was significantly recovered when referencing correct somatosensory information with the intact hand. Furthermore, motor control of the intact hand was impaired when referencing abnormal somatosensory information with the affected hand. Such bilateral limb interference suggests that there is only one common integrated sensory representation and only one common motor representation for both hands. The single sensory representation would be integrated from the somatosensory information received from both hands. Subsequently, the integrated motor representation would be derived from the integrated sensory representation, and would then be split and sent out via motor commands to both hands. Considering that bimanual coordinated movements are reportedly smoother than unimanual movements, information transfer between the integrated sensory and the integrated motor representation would be suitable for such efficient bimanual movements. Therefore, we propose a novel hypothetical model to better explain the observation of bilateral limb interference. The proposed model might contribute to the development of novel sensory and motor rehabilitation strategies by promoting the use of the unaffected hand.