Brain games.
A quadriplegic patient outfitted with an electrode array (top) was able to operate a computer.

L. Hochberg et al., Nature 442, 164 (2006)

Mind Over Matter

Using an array of hair-thin electrodes implanted in his brain, a 25-year-old quadriplegic man was able to operate a computer, open and close a prosthetic hand, and manipulate a robotic arm just by thinking about it, according to a new study. Such a brain-computer interface may one day help restore movement and communication to people paralyzed from spinal cord injuries, strokes, and disorders such as muscular dystrophy and amyotrophic lateral sclerosis.

Researchers have previously inserted single electrodes into paralyzed people, providing them with limited computer cursor control. They've also put more complicated electrode arrays into monkeys (ScienceNOW, 8 July 2004). But no one had ever put a large number of microelectrodes into a paralyzed person; indeed, no one knew whether neurons in the motor cortex, the brain region primarily responsible for movement control, would still produce decipherable signals after years of disuse.

In a pilot study, two quadriplegic patients underwent a 3-hour surgery. Neurosurgeons attached the electrode array, called BrainGate, to a small pedestal on top of each patient's head, from which wires stretch to a computer. The research team, led by Brown University neuroscientist John Donoghue, then asked each man to think about moving his hand to follow a cursor on a screen--and to the team's delight, the patterns of activity in the motor cortex changed according to the direction of motion each man was told to imagine. "As soon as he started thinking about left and right, the motor cortex was active," says Donoghue, who also leads research at Cyberkinetics Neurotechnology Systems in Foxborough, Massachusetts, which manufactures BrainGate.

The next step was translating these thoughts into cursor movement. To do this, scientists had to program a customized neural decoder for each patient. The software allowed the men to move a cursor around a computer screen with far more facility than had been achieved in previous experiments with implanted electrodes in humans. From there, the researchers demonstrated how this simple skill could be used to control a computer and other devices. With appropriate software, the first patient easily opened simulated e-mail, drew a circle, changed TV channels, made a robot arm grab a piece of candy and drop it a short distance away, and pinched Donoghue with a prosthetic hand. The results are described in this week's Nature. Says coauthor Leigh Hochberg, a Massachusetts General Hospital neurologist: "We may be able to get finer control over an external device than was previously possible."

BrainGate is still years from clinical practice, but researchers are hailing the result. "This meticulous case report is valuable and encouraging," says Jonathan Wolpaw, a neuroscientist at the Wadsworth Center, part of the New York State Department of Health in Albany. Adds Stephen Scott, a motor-cortex neurophysiologist at Queen's University in Kingston, Canada, "[it's] a major step forward."

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