Significant research and development into prosthetic limbs has yielded effective human control through various sensing interfaces. Yet, a major remaining challenge for controlling a prosthetic arm is the communication from the device back to the user’s phantom limb — the sensation that an amputated or missing limb is still attached.

In exploring ways to make it easier for users to control a prosthesis, researchers at the Johns Hopkins Applied Physics Laboratory (APL) Intelligent Systems Center (ISC), in Laurel, Maryland, found that giving them sensory stimulation enhances the perception of their phantom hand and leads to more reliable and repeatable muscle movement signals, which are used to control a prosthetic arm. Their most recent findings, “Sensory Stimulation Enhances Phantom Limb Perception and Movement Decoding,” were published in the Journal of Neural Engineering.

Luke Osborn, who specializes in noninvasive nerve stimulation for sensory feedback, tactile sensor development and upper-limb prosthesis, led a team that tracked one participant over time and found phantom hand improvements performed the same day sensory stimulations were enacted. 

“We used a technique we are calling ‘targeted’ transcutaneous electrical nerve stimulation — or tTENS – that allows us to electrically stimulate small regions of the skin on an amputated arm and create sensations of touch in the phantom hand,” Osborn explained.  “We think this technique could help make it easier for users to control a prosthetic arm.”

The application of this technique to improve the rehabilitation of sensorimotor skills of any user relying on EMG signals to control their prosthesis has the potential to impact a range of rehabilitation techniques and therapies.