Neural control of artificial limbs

Upper limb amputees desire an artificial arm that allows for multiple degrees of freedom of control over the movements of the prosthesis, coupled with direct sensory feedback. The goal of this work was to assess if it is feasible to interface artificial limbs to severed nerves of human upper limb amputees. Longitudinal intrafascicular electrodes were interfaced to severed nerve stumps of long-term human amputees. Initial studies conducted for two days following electrode implantation showed that it is possible to provide discrete, unitary, painless, graded sensations of touch, joint movement and position referred to the missing limb. Amputees were able to generate and control motor nerve activity uniquely associated with the missing limb movements. Longer term studies conducted for a period of up to 4 weeks showed recorded motor nerve activity and elicited sensations remained stable and there was no significant change in the stimulation parameters. Finally, amputees were able to control a modified Utah Artificial Arm. Results of our studies show that it is possible to interface an artificial limb to the severed nerves of upper limb amputees. Further work is required to refine the hardware which can be eventually incorporated into the artificial arm, allowing the amputees to wear the prosthesis and more precisely execute movements related to real life activities of daily living.