February 28, 2011

Moving Arm with Thoughts Alone

(Ivanhoe Newswire) -- It sounds like science-fiction, but one researcher has used new technology that may someday allow patients with a prosthetic arm to move their limb by thought alone.

Daniel Moran, Ph.D., associate professor of biomedical engineering and neurobiology in the School of Engineering & Applied Science at Washington University in St. Louis, and colleagues just completed a set of experiments that employed the use of brain-computer interfaces (BCIs) called EECoGs. These are grids of disk-like electrodes that lie inside the skull but outside the dura mater -- a membrane that covers and protects the brain. The researchers built a 32-channel EECoG grid that is small enough to fit within the boundaries of the sensorimotor cortex of the brain.

The next step is to slip the grid under a monkey's skull and train him to control a computational model arm strictly by thinking about it. The arm will have seven degrees of freedom including rotation about the shoulder joint, flexion and extension of the elbow, pronation and supination of the lower forelimb, and flexion, extension, abduction and adduction of the wrist.

With his virtual hand, the monkey will be asked to trace three circles that intersect in space at 45 degrees to one another. Because this task better separates degrees of freedom, it will be easier for the scientists to map cortical activity to details of movement.

Moran expects that his experiment will be a success, and if it is, he would like to someday connect his EECoG BCI to a new peripheral nerve-stimulating electrode he is developing with other researchers. By connecting these two devices, the scientists will be able to create a neuroprosthetic arm, which is a paralyzed arm that can move again because the mind sends signals to peripheral nerves that stimulate muscles to expand or contract.

"My passion is for paralyzed individuals," Moran was quoted as saying. "But, you can see down the road that a lot of people will want one of these devices."

In 2006, Moran and colleagues showed that a young patient who was in the hospital to treat intractable epilepsy could play the videogame "Space Invaders" just by thinking about it. Only two degrees of freedom were needed to move the Space Invaders cursor in a two-dimensional plane.

SOURCE: Washington University in St. Louis