Vibrotactile Stimulation Promotes Embodiment of an Alien Hand in Amputees With Phantom Sensations

Abstract

Tactile feedback is essential to intuitive control and to promote the sense of self-attribution of a prosthetic limb. Recent findings showed that amputees can be tricked to experience this embodiment, when synchronous and modality-matched stimuli are delivered to biological afferent structures and to an alien rubber hand. Hence, it was suggested to exploit this effect by coupling touch sensors in a prosthesis to an array of haptic tactile stimulators in the prosthetic socket. However, this approach is not clinically viable due to physical limits of current haptic devices. To address this issue we have proposed modality-mismatched stimulation and demonstrated that this promotes self-attribution of an alien hand on normally limbed subjects. In this work we investigated whether similar effects could be induced in transradial amputees with referred phantom sensations in a series of experiments fashioned after the Rubber Hand Illusion using vibrotactile stimulators. Results from three independent measures of embodiment demonstrated that vibrotactile sensory substitution elicits body-ownership of a rubber hand in transradial amputees. These results open up promising possibilities in this field; indeed miniature, safe and inexpensive vibrators could be fitted into commercially available prostheses and sockets to induce the illusion every time the prosthesis manipulates an object.

Surface electrical stimulation to evoke referred sensation

“…Sensory substitution methods use electrocutaneous stimulation [2][3] or vibrotactile stimulation [4] to translate information such as grip force to the residual limb of the user. Haptic methods employ mechanisms such as force applicators [5] or pneumatic bladders [6] to provide a more realistic sensation of touch or pressure, but still on the residual limb.…”

A System for Electrotactile Feedback Using Electronic Skin and Flexible Matrix Electrodes: Experimental Evaluation

“…The information from multiple contact points can be used by the embedded prosthesis controller to automatically evaluate the grasp stability, control grip formation and/or prevent slipping [22]. In the context of feedback to the user, such sensors are comprehensive sources of tactile signals, which can be utilized to provide an unprecedented level of afferent inflow, facilitating thereby the integration of the prosthetic device and the user body and mind, as proposed conceptually in [23]- [25], and stimulating the cognitive and psychological mechanisms related to body ownership [26]. Some recent sensors also implement biologically-inspired coding of the tactile information.…”

Approximate FPGA Implementation of CORDIC for Tactile Data Processing Using Speculative Adders

“…Closing this loop in the prosthesis control would allow better control of grasping and manipulation. In addition, it is hypothesized that this could enhance the utility as well as improve the embodiment of such artificial system as this tactile information could stimulate the psychological and cognitive mechanisms related to body ownership [3].…”