To make this possible, the physicians and engineers on the Johns Hopkins team first selected an epilepsy patient who was already scheduled for brain mapping surgery. While neurosurgeons looked to identify the origin of the patient’s seizures, operators placed a piece of film the size of a credit card on the part of the brain that typically controls movement of the arms and hands. An array of 128 electrodes on the film allowed scientists to see which parts of the patient’s brain were engaged when they asked him to move each individual finger one by one.
Having identified the specific parts of the brain that controlled each finger’s movement, the scientists also worked to understand the electrical brain activity required to experience the sensation of touch. The patient was then asked to wear a glove fitted with a small buzzer in each fingertip, and scientists were able to measure the corresponding electrical activity in the brain when each fingertip buzzer was activated.
All of this data contributed to the computing-based elements of the prosthetic. The team programmed the prosthetic arm to move each finger in response to electrical activity in the corresponding part of the brain. That way, the wearer merely had to think of the specific finger in order to make it move. Each finger was programmed separately, except for the ring finger and pinkie finger (which most people move in tandem anyway). Overall, the mind-controlled prosthetic has already attained 88 percent accuracy.
It’s a big achievement, not doubt — but scientists on the project are aware that a successful application of this prototype for someone who has actually lost a limb is a long way off. The research and testing required will be time-consuming and costly, but once accomplished, could make an enormous difference to people living without hands or arms.