Advances in prosthetic arm technology provide users with the ability to grasp and manipulate objects but have no capacity to deliver sensory feedback. Implanted electrodes can provide a small measure of peripheral nerve stimulation to provide sensory feedback and improve prosthetic control but require complex surgeries and equipment. Available spinal cord stimulators usually used to treat chronic pain were demonstrated by University of Pittsburgh researchers to offer a more intuitive means to transmit sensory information to the nervous system.

Infinion electrode leads from Boston Scientific were implanted near the spinal cords, above the nerve roots that relay sensations from the arm, of four volunteers and connected to Nano 2+Stim stimulators from Ripple Inc. Spinal stimulation was shown to recreate tactile sensations on the missing limb. Source: University of PittsburghThe devices, which have multiple stimulation points, were then energized in different spots, using signals typically applied to tackle pain.

The participants reported sensations somewhere on their missing arm or hand, and three indicated feelings localized to a single finger or part of the palm. All four reported feeling natural sensations such as touch and pressure, though these feelings were often mixed with tingling and other artificial sensations.

The research published in eLife demonstrates the potential of commercially available spinal cord stimulators to be effective for restoring sensation in people with upper-limb amputations. The researchers will next focus on designing spinal stimulators that can be fully implanted rather than connecting to a stimulator outside the body. Miniaturizing the electrode contacts, which might allow users to experience more localized sensations, will also be pursued.