Plenary talks The touch of a hand: Neural interfaces restore the sense of touch and position following limb loss

One of the first biology lessons in grade school is of the five senses: sight, sound, smell, taste, and touch. They are the (only) connection to the world and people around us. Of the five senses, touch is the one we take most for granted and least understand the devastating impact of its loss. The sense of touch comes from the skin, the largest sensory organ in the human body. For nearly 2 million people in the US and 185,000 more each year, the loss of sensation is one of the most significant effects of limb loss resulting from trauma or vascular disease. Body-powered prostheses are often preferred over more functional powered devices because the user can “feel” the pressure of a grip through a requisite body harness. Providing representative sensory information on the residual limb is unnatural and does not directly match the sensory locations expected by the user's visual experience of the prosthesis. We have addressed these challenges with permanently implanted, multi-contact nerve cuff electrodes on the residual ulnar, radial, and median nerves of subjects with limb loss. These electrodes directly and selectively activate the peripheral neural pathways, and hence all upstream pathways, normally responsible for sensation. Ninety percent of the channels produce physically unique locations of sensation, distributed around the hand and wrist. The quality of the sensation is controlled by using a patterned stimulation intensity. The pattern pulses are critical to the brain's interpretation of the sensation. Varying the pattern can produce multiple different sensations at a common location. The addition of sensation to the user during tasks improves fine motor control with standard myoelectric prostheses. The system has been implanted and stable for three years. The user reports feeling their hand - the missing hand - in touching and manipulating objects. Restoring feeling has allowed the individuals to, “feel [my] hand for the first time since the accident,” and “feel [my] wife touch my hand.” With more than five subject-years of experience, this work is leading the evolution of a new era in prostheses and haptic interfaces.