Sub-motor threshold transcutaneous spinal cord stimulation elicits proprioceptive sensations in the phantom hand

Restoring sensory function lost by amputation remains a major challenge in prosthetics research. Peripheral nerve stimulation and targeted reinnervation techniques may partially restore somatotopic sensory feedback but their widespread adoption is hindered by the need for surgical interventions. In a study involving 17 able-bodied participants and five individuals with upper-limb amputation, we show that transcutaneous spinal cord stimulation (tSCS) can evoke proprioceptive sensations—such as movement, touch, and tapping—that appear to originate from the missing limb. Notably, these perceptions were primarily isolated to the phantom limb and were largely absent in the stump. Additionally, amputee participants experienced an increased level of comfort during tSCS. We further characterized how various stimulation parameters, such as electrode placement, carrier frequency, and burst frequency, modulated the quality and type of perceived sensations. Additionally, we show that tSCS maintained force proprioception necessary for effective prosthesis control. These results underscore the potential use of tSCS to provide sensory feedback for upper-limb prosthetics.