Brain implant passes 1,000 day mark

BROWN (US) — A tetraplegia patient with an implanted brain-computer interface was able to control a computer cursor accurately through neural activity alone more than 1,000 days after receiving the implant.

Results from five consecutive days of device use surrounding her 1,000th day in the trial is published online in the Journal of Neural Engineering.

“This proof of concept—that after 1,000 days a woman who has no functional use of her limbs and is unable to speak can reliably control a cursor on a computer screen using only the intended movement of her hand—is an important step for the field,” says Leigh Hochberg, associate professor of engineering at Brown University and a visiting associate professor of neurology at Harvard University.

The patient, identified in the paper as S3, performed two “point-and-click” tasks each day by thinking about moving the cursor with her hand, averaging greater than 90 percent accuracy. Some on-screen targets were as small as the effective area of a Microsoft Word menu icon.

“Our objective with the neural interface is to reach the level of performance of a person without a disability using a mouse,” says report lead author John Simeral, assistant professor of engineering at Brown. “These results highlight the potential for an intracortical neural interface system to provide a person that has locked-in syndrome with reliable, continuous point-and-click control of a standard computer application.”

Under development since 2002, the investigational BrainGate system is a combination of hardware and software that directly senses electrical signals produced by neurons in the brain that control movement.

By decoding signals and translating them into digital instructions, the system is being evaluated for its ability to give people with paralysis control of external devices such as computers, robotic assistive devices, or wheelchairs.

The system is currently in pilot clinical trials, directed by Hochberg at Massachusetts General Hospital.

BrainGate uses a silicon electrode array about the size of a baby aspirin to read neural signals directly within brain tissue. Although external sensors placed on the brain or skull surface can also read neural activity, they are believed to be far less precise. Several prototype brain implants have eventually failed because of moisture or other perils of the internal environment.

“Neuroengineers have often wondered whether useful signals could be recorded from inside the brain for an extended period of time,” Hochberg says. “This is the first demonstration that this microelectrode array technology can provide useful neuroprosthetic signals allowing a person with tetraplegia to control an external device for an extended period of time.”

Device performance was not the same at 2.7 years as it was earlier on, Hochberg adds. “None of us will be fully satisfied with an intracortical recording device until it provides decades of useful signals.”

“Nevertheless, I’m hopeful that the progress made in neural interface systems will someday be able to provide improved communication, mobility, and independence for people with locked-in syndrome or other forms of paralysis and eventually better control over prosthetic, robotic, or functional electrical stimulation systems (stimulating electrodes that have already returned limb function to people with cervical spinal cord injury), even while engineers continue to develop ever-better implantable sensors.”

The research was funded in part by the Rehabilitation Research and Development Service, Department of Veterans Affairs; The National Institutes of Healththe Doris Duke Charitable Foundation; MGH-Deane Institute for Integrated Research on Atrial Fibrillation and Stroke; and the Katie Samson Foundation.

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