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Device Technologies and Biomedical Robotics

Device Technologies and Biomedical Robotics - Poster Session D

Poster I16 - Performance using three-dimensional supplemental vibrotactile feedback to guide reach-to-grasp tasks varies with number of task repetitions

Friday, October 25, 2024
3:30 PM - 4:30 PM EST
Location: Exhibit Hall E, F & G

Introduction:  The practice of sensorimotor tasks leads to improved skill, decreased cognitive load, and the development of habitual action selection. Recent research shows that increased time-on-task (i.e., duration of session) leads to increased perceived quality of movement for stroke survivors. Previous work shows that time-on-task training with vibrotactile feedback (VTF) about hand position can enhance the accuracy of 2-dimensional reaching tasks for healthy individuals and some survivors of stroke. However, it remains unknown the extent to which the number of repetitions completed within a fixed time-on-task affects movement quality. For this current study, healthy controls and stroke survivors executed reach-to-grasp movements with 3-dimensional supplemental VTF for fixed 30-minute sessions (user-determined task repetition). We hypothesize a negative correlation between the number of VTF training trials completed in 30 minutes and the mean session error across all sessions for both groups (i.e., more practice aligns with greater accuracy). Additionally, we hypothesize a difference in the number of VTF training trials completed in 30 minutes between stroke survivors and healthy controls.

Materials and

Methods:  Five individuals (2 stroke survivors; 3 healthy controls) sat in a chair with gravity support for their reaching arm (stroke: more affected; control: dominant). Participants completed reach-to-grasp tasks holding a squeeze ball with an integrated active infrared marker. A motion capture system (OPTOTRAK 3020) collected and converted real-time positions to a user-based reference system. The stationary arm (stroke: less affected; control: non-dominant) received VTF of hand position via six eccentric rotating mass motors placed on the hand, forearm, and shoulder to represent deviations from the middle of the user’s unique workspace (±x, ±y, ±z). The participant’s arm was visually blocked to require reliance on proprioceptive feedback and supplemental VTF for target capture. A set of 100 targets were used for training. Participants underwent 18 training sessions, each consisting of 30 minutes of VTF training. Training comprised of point-to-point reaches performed with concurrent VTF but without ongoing visual feedback of performance; intertrial corrections were performed with both VTF and concurrent visual cursor feedback of 3D hand position. Participants were instructed to move from target to target at a comfortable pace and were provided with a 2-minute break after every 10 minutes of training. To test our first hypothesis, we performed a correlation analysis between the number of trials completed per session and mean session error. To test our second hypothesis, we performed a t-test to compare the 18-session average number of trials completed per session between stroke survivors and healthy controls.

Results, Conclusions, and Discussions: Preliminary results show a general reduction in mean session error from the first to last training sessions for both groups. Correlation analysis supported our first hypothesis by revealing a significant negative relationship between the number of VTF training trials completed in 30 minutes and the mean session error across all 18 training sessions (r(16) = -0.53, p = 0.022). Contrary to our second hypothesis, the planned t-test did not find a significant difference between the control and stroke groups’ average number of trials completed across the 18 sessions (t(3) = 0.019, p = 0.99). An exploratory single-factor ANOVA revealed a group effect for the mean session error (F(1,3) = 13.08, p = 0.036); surprisingly, stroke survivors performed with less mean error than healthy controls.
To further explore this surprising effect, we considered the extent to which participant age may correlate with error reduction. We performed an exploratory correlation analysis between mean session error and participant age (r(3) = 0.80, p = 0.10). Given these equivocal results and our small sample size, more data needs to be collected and multiple regression analyses conducted to disentangle the potential effects of age and number of trials on mean session error.
In conclusion, results show that more task repetitions correlate with greater reach-to grasp accuracy. There did not appear to be a group effect for the number of task repetitions completed per 30-minutes time-on-task, thereby demonstrating that stroke survivors and healthy controls can practice reach-to-grasp actions guided by supplemental VTF.

Acknowledgements (Optional):  This work was supported by the National Institute of Child Health and Human Development grant 2R15HD093086.