Bionic Arm Taps New Part of Brain for Smooth Moves

Mind-controlled prosthetic limbs have been a reality for a few years, but researchers have not found ways to give the people who use them the same, smooth motor control that people have over their natural limbs.

Now, a team of researchers says the members have solved part of the problem of smooth motor control by connecting an artificial limb to a different part of the brain. Previous designs for mind-controlled prostheses linked the artificial limb to either the person’s motor cortex or the individual’s premotor cortex, which both translate signals from the brain to the limbs.

This time, the connections to the robotic arm were wired into a patient’s posterior parietal cortex, which is located on the side of the head near the ear.

“The [posterior parietal cortex] forms the initial plans to make movements,” said Richard Andersen, a professor of neuroscience at the California Institute of Technology and one of the researchers who developed the new prosthesis. For example, when a person decides to grab a coffee cup, the posterior parietal cortex outlines the steps in movement, then, the motor cortexes translate that plan into actual signals that are sent to specific parts of the arm.

The researchers used signals from the posterior parietal cortex “to extract the intent of the subject,” Andersen told Live Science. “Instead of ‘I want to control muscles,’ we can use smart robotics to work out the fine details” of the movement a person wants to make.

In a report published in the May 22 issue of the journal Science, the researchers explain how they connected the posterior parietal cortex of one patient, Erik G. Sorto, to a computer that acted as a kind of artificial motor cortex. The computer used specific signals from the parietal cortex to detect what kind of movement Sorto intended to make, and then translated that into signals for the robotic arm.

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