Brain-Machine Interface
Biomedical scientists have successfully demonstrated a robotic prosthetic brain-machine interface that allowed a subject to move the individual fingers of a prosthetic hand with their thoughts.
Johns Hopkins physicians and biomedical engineers have reported what they believe is the first successful effort to wiggle fingers individually and independently of each other on a mind-controlled robotic arm without a large amount of training.
"We believe this is the first time a person using a mind-controlled prosthesis has immediately performed individual digit movements without extensive training."
The results of the study which are, published in the Journal of Neural Engineering, represents a potential advance in technologies to restore refined hand function to those who have lost arms to injury or disease. The subject of the experiment, which can be seen in a video below, was not missing an arm or hand, but he was outfitted with a device that essentially took advantage of a brain-mapping procedure to bypass control of his own arm and hand.
While brain recordings were made using electrodes surgically implanted for clinical reasons, the signals also control a modular prosthetic limb. Before connecting the prosthesis, the researchers mapped and tracked the specific parts of the subject’s brain responsible for moving each finger, then programmed the prosthesis to move the corresponding finger.
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For the procedure, the patient’s neurosurgeon placed an array of 128 electrode sensors — all on a single rectangular sheet of film the size of a credit card — on the part of the man’s brain that normally controls hand and arm movements. Each sensor measured a circle of brain tissue 1 millimeter in diameter.A computer program then had the man move individual fingers on command and recorded which parts of the brain the “lit up” when each sensor detected an electric signal.
The researchers also measured electrical brain activity involved in the patient's sense of touch. The subject was outfitted with a glove with small, vibrating buzzers in the fingertips, which went off in each finger. The researchers then measured the resulting electrical activity in the brain for each finger connection.
Using this data, the researchers programmed the robotic arm to move corresponding fingers based on which part of the brain was active. Turning on the prosthetic arm, which was wired to the patient through the brain electrodes, they then asked the subject to “think” about individually moving thumb, index, middle, ring and pinkie fingers. The electrical activity generated in the brain moved the fingers.
The researchers claim there was no pre-training required for the subject to gain this level of control, and the entire experiment took less than two hours.
At first, the brain-machine interface had an accuracy of 76 percent, but once the researchers coupled the ring and pinkie fingers together, the accuracy increased to 88 percent.
“The part of the brain that controls the pinkie and ring fingers overlaps, and most people move the two fingers together,” says Crone. “It makes sense that coupling these two fingers improved the accuracy.”
Crone cautions that application of this technology to those actually missing limbs is still some years off and will be costly, requiring extensive neural mapping and computer programming. Despite the work needed, the research is impressive.
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