Grasping at illusions: stimulating cutaneous afferents to create kinesthetic illusions
摘要
Most evidence for the role of muscle and cutaneous receptors in kinesthesia comes from studies that induce kinesthetic illusions. Such movement illusions are created by artificially stimulating these receptors or their afferents to mimic their natural discharge. Previous research to investigate the contribution of cutaneous receptors to kinesthesia used electrical stimulation arranged in arrays across the back of the hand. In the present study, we introduce a simple technique to stimulate a cutaneous nerve at the wrist (superficial branch of radial nerve) through two electrodes and quantified the resulting illusory movements. We modulated stimulation frequency and current, both separately and simultaneously, and delivered a control (unmodulated) stimulation. To assess the prevalence and amplitude of any movement illusions, we quantified matching movements made with the left (unstimulated) hand. We hypothesised that modulating either the frequency or current would evoke illusions of finger movements, and that combined modulation would increase illusion prevalence and amplitude. The stimulation elicited illusory movements in 25/34 (74%) participants. The combined modulation did not significantly increase illusion prevalence or amplitude compared to modulating either parameter alone. All three modulated stimulation patterns produced significantly larger illusions in more participants than the control. These findings support the idea that cutaneous receptors are important for kinesthesia and that both rate coding and population coding of cutaneous feedback are used when making kinesthetic judgements. This simple technique is a promising method for studying cutaneous contributions to kinesthesia and may inform the development of advanced sensory feedback systems for prosthetics and immersive technologies.