Study of the Effect of Distance-Based Plantar Cutaneous Electrotactile Feedback on Lateral Balance

Abstract

Our sense of balance and body movement heavily rely upon sensory feedback from our lower limbs, as well as other sensory modalities including visual and vestibular feedback. If the sensory feedback from the lower limb is affected by problems such as diabetes or nerve impairments, it often results in falling and unnecessary cognitive engagement even during simple walking. To address this problem, various approaches of sensory augmentation have been investigated, using visual, auditory, tactile sensory pathway. However, the efficacy of these sensory augmentation approaches is still controversial. One of the important reasons is that these sensory augmentations are often applied to the area not directly associated with the target motor task, resulting in a detour of the sensory pathway via prefrontal cortex and requiring additional cognitive efforts to process the afferent signal.

To address the current limitations, we propose a novel method of evoking distance-based electrotactile feedback on the foot sole. The distance-based electrotactile feedback will inform the subjects via the intrinsic sensory pathway for balancing as a compensatory sensory feedback for proprioception. We hypothesize that the distance-based electrotactile feedback will improve the lateral balance at challenging ground condition. We also hypothesize that the distance-based electrotactile feedback will be more effective than the discrete electrotactile feedback in improving lateral balance. Three subjects have so far participated in this experiment. We first identified the most effective location to apply electrical stimulation (E-stim), then we identified the optimal amplitude and range of frequency required for the E-stim, and finally tested the balancing ability on the balance board with a challenging sensory condition. Our results from 10 subjects showed that the distance-based proportional E-stim significantly increased balancing time compared to that with the distance-based discrete E-stim or the control condition (no E-stim). This result suggests that the distance-based proportional E-stim can be an effective way of augmenting sensory feedback to enhance balance in challenging sensory condition and proves a vital concept for improving human-computer interaction.