Robot-Assisted Proprioceptive Training with Added Vibro-Tactile Feedback Enhances Somatosensory and Motor Performance

Abstract

This study examined the trainability of the proprioceptive sense and explored the relationship between proprioception and motor learning. With vision blocked, human learners had to perform goal-directed wrist movements relying solely on proprioceptive/haptic cues to reach several haptically specified targets. One group received additional somatosensory movement error feedback in form of vibro-tactile cues applied to the skin of the forearm. We used a haptic robotic device for the wrist and implemented a 3-day training regimen that required learners to make spatially precise goal-directed wrist reaching movements without vision. We assessed whether training improved the acuity of the wrist joint position sense. In addition, we checked if sensory learning generalized to the motor domain and improved spatial precision of wrist tracking movements that were not trained. The main findings of the study are: First, proprioceptive acuity of the wrist joint position sense improved after training for the group that received the combined proprioceptive/haptic and vibro-tactile feedback (VTF). Second, training had no impact on the spatial accuracy of the untrained tracking task. However, learners who had received VTF significantly reduced their reliance on haptic guidance feedback when performing the untrained motor task. That is, concurrent VTF was highly salient movement feedback and obviated the need for haptic feedback. Third, VTF can be also provided by the limb not involved in the task. Learners who received VTF to the contralateral limb equally benefitted. In conclusion, somatosensory training can significantly enhance proprioceptive acuity within days when learning is coupled with vibro-tactile sensory cues that provide feedback about movement errors. The observable sensory improvements in proprioception facilitates motor learning and such learning may generalize to the sensorimotor control of the untrained motor tasks. The implications of these findings for neurorehabilitation are discussed.

Supplemental vibrotactile feedback of real-time limb position enhances precision of goal-directed reaching

“…Two novel aspects of our experimental approach likely contributed to the rapid learning observed in our study (i.e., the reduction of drift and the reduction in the expansion of endpoints seen Figs 4, 6, and 7). First and foremost, vibrotactile feedback encoded limb state information in our study rather than performance error information, as used by most previous studies of sensory augmentation via vibrotactile stimulation (e.g., Bark et al, 2015;Cuppone et al, 2016). In any case, beneficial effects of vibrotactile limb state feedback reflect its partial integration into the online control of movement because some benefits were seen only while the vibrotactile signals were present; upon removal of the vibrotactile signals on Day 1, target capture errors increased, as did the amount of drift and the area spanned by the reach endpoints.…”

“…Cuppone and colleagues have also found a persistent improvement of motor performance after a training based on concurrent vibrotactile and haptic feedback (Cuppone et al, 2016). In that study, groups of subjects grasped the handle of wrist manipulandum and were tested pre-and post-training in their ability to perform a 2-DOF (flexion/extension, abduction/adduction) position matching task and a 2-DOF target tracking task.…”

“…The first proposes that neurologically-intact subjects can learn to use supplemental vibrotactile feedback of hand position to enhance the ongoing control of reaching movements beyond limits imposed by intrinsic proprioception. The second proposes that this training has aftereffects on subsequent movements performed without concurrent supplemental limb state feedback (i.e., that training induces improved proprioceptive control; c.f., Cuppone et al, 2016). To test these hypotheses, we compared target capture error across feedback conditions and days.…”

“…with notable examples being robotic re-training of proprioception (Cuppone et al, 2015;Cuppone et al, 2016;De Santis et al, 2015;Wong et al, 2011) and the application of supplemental performance feedback using vibrotactile stimulation (c.f., Bark et al, 2011;Krueger et al, 2017;Lieberman and Breazeal, 2007;Tzorakoleftherakis et al, 2015). Building on that foundation, a long-term goal of our work is to re-establish or enhance closed-loop control of goal-directed behaviors in individuals with impaired kinesthesia by creating sensory substitution technologies that provide real-time feedback of the moving limb's state (e.g., position and velocity of the arm and hand) to a site on the body retaining somatosensation (such as the ipsilesional arm).…”

“…At the same time, we implemented a vibrotactile display of the arm's planar work space wherein a hand displacement corresponding to the grid's minimum inter-target distance also corresponded to a change in vibrotactile stimulation that was greater than three times the just-noticeable differences in the magnitude of that stimulus, as reported by Shah and colleagues (Shah et al, 2016). These design choices enabled us to test two main hypotheses: (1) that neurologically-intact humans can learn to use vibrotactile limb state feedback to enhance the on-going control of a moving limb beyond the limits of intrinsic proprioception; and (2) that this training has aftereffects on subsequent movements performed without concurrent supplemental vibrotactile feedback (i.e., that training induces improved proprioceptive control; c.f., Cuppone et al, 2016). Preliminary aspects of this study have been presented in abstract form (Risi et al 2016(Risi et al , 2017.…”