A New Visual-Electrotactile Mapping by Distance Based Electrical Stimulation Improves the Control Accuracy of Finger Aperture
Abstract
Finger motor tasks often need high manipulation accuracy because the fingers are frequently used in sophisticated tasks. Finger aperture control (the gap between a pair of fingers e.g., thumb and index) in a finger reaching task is one of the critical maneuvers for surgical operation, to grab and manipulate the tissue structures. The planning and execution of such a finger reaching task to control the finger aperture is based on the visual and proprioceptive feedback. The visual and proprioceptive feedback is integrated optimally to provide a minimum-variance estimation of the position of the fingers i.e., each estimate of the sensory feedback is combined as their weighted averages where the weights are inversely proportional to the variance of the estimates. However, the visual-proprioceptive mapping error due to the mismatch between an allocentric visual feedback, specialized to perceive the body position relative to the target, and an egocentric proprioceptive feedback, specialized to perceive the intrinsic spatial representation of the body, limits the sense of distance perception between our hand and an object accurately before touching it, resulting in an error in the motor output. To adjust the visual-proprioceptive mapping error and truly improve the control accuracy of the finger aperture, we introduce distance-based electrotactile feedback which works as the new sensory reference optimally combining with the original visual and proprioceptive feedbacks. The electrotactile stimulation was applied with a frequency inversely proportional to the finger aperture distance. We tested the efficacy of the distance-based E-stim against conventional visual sensory feedback method, on enhancing the accuracy of the interactive finger reaching. We observed that the control accuracy of the finger aperture significantly improved on application of the stimulation (p < 0.0001) compared to the baseline value. Moreover, on removal of the stimulation, the control accuracy decreased slightly but still significantly improved compared to its baseline value (p < 0.0001) indicating a retention of the finger aperture accuracy even after the removal of stimulation. We believe that the new electrotactile method generates a new schema of representing visual target in the tactile working memory of the brain resulting in a longer retention.
Subject
electrical stimulationfinger aperture
control accuracy
visual-proprioceptive mapping
finger reaching
visual feedback
electrotactile feedback
proprioceptive feedback
Citation
Ravichandran, Rachen (2021). A New Visual-Electrotactile Mapping by Distance Based Electrical Stimulation Improves the Control Accuracy of Finger Aperture. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /195213.