Sensory adaptation to electrical stimulation of the somatosensory nerves

Emily L Graczyk,Dustin J Tyler,Benoit P Delhaye,Sliman J Bensmaia,Matthew A Schiefer

doi:10.1088/1741-2552/aab790

Abstract

Objective. Sensory systems adapt their sensitivity to ambient stimulation levels to improve their responsiveness to changes in stimulation. The sense of touch is also subject to adaptation, as evidenced by the desensitization produced by prolonged vibratory stimulation of the skin. Electrical stimulation of nerves elicits tactile sensations that can convey feedback for bionic limbs. In this study, we investigate whether artificial touch is also subject to adaptation, despite the fact that the peripheral mechanotransducers are bypassed. Approach. Using well-established psychophysical paradigms, we characterize the time course and magnitude of sensory adaptation caused by extended electrical stimulation of the residual somatosensory nerves in three human amputees implanted with cuff electrodes. Main results. We find that electrical stimulation of the nerve also induces perceptual adaptation that recovers after cessation of the stimulus. The time course and magnitude of electrically-induced adaptation are equivalent to their mechanically-induced counterparts. Significance. We conclude that, in natural touch, the process of mechanotransduction is not required for adaptation, and artificial touch naturally experiences adaptation-induced adjustments of the dynamic range of sensations. Further, as it does for native hands, adaptation confers to bionic hands enhanced sensitivity to changes in stimulation and thus a more natural sensory experience.

Highlights

Adaptation—the progressive desensitization to prolonged, suprathreshold stimulation—is a ubiquitous phenomenon in the nervous system, one that has been extensively documented in all sensory systems
Using well-established psychophysical paradigms, we characterize the time course and magnitude of sensory adaptation caused by extended electrical stimulation of the residual somatosensory nerves in three human amputees implanted with cuff electrodes
We find that electrical adaptation of artificial touch shares the same magnitude and time course as vibrotactile adaptation of natural touch

Summary

Introduction

Adaptation—the progressive desensitization to prolonged, suprathreshold stimulation—is a ubiquitous phenomenon in the nervous system, one that has been extensively documented in all sensory systems. The function of adaptation is to adjust sensitivity to reduce responsiveness to ambient stimulation levels and to promote responsiveness to changes in stimulation (Brenner et al 2000). The sense of touch is subject to adaptation, as evidenced by the progressive perceptual and neuronal desensitization caused by prolonged vibrotactile stimulation of the skin. Suprathreshold vibrotactile stimulation results in an increase in detection threshold and a progressive decrease in the subjective magnitude of the

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