Researchers have wired up the brains of monkeys to computers, giving them the tools to use thought to move a cursor around a computer screen. By demonstrating how the brain controls the manipulation of objects in two-dimensional space, bioengineers have taken another step toward designing new, finely tuned devices for paralyzed individuals.
So-called neuroprosthetic devices aim to let brain cells guide robotic arms or computers, but research so far has focused on one-dimensional movements--rats outfitted with electrodes can learn to move a lever up and down without using their paws. A recent study with monkeys did manage more elaborate movements, but in that case the animals' brain signals were translated to a computer program, which was then able to move a robotic arm.
To get the monkeys rather than a computer performing comparable motions, neuroscientist Mijail Serruya and his colleagues at Brown University in Providence, Rhode Island, first taught monkeys a simple computer game: A red dot appears at random on the screen, and the monkey uses the computer mouse to click on that spot. When the cursor hit the target, the monkey receives a reward and the red dot disappears, reappearing elsewhere.
Having trained the animals to play the game, the team then implanted about 100 electrodes into each monkey's motor cortex. The animals played the game with the mouse while a computer gathered data on which neurons sent the monkey's hand in different directions. After the computer identified which neurons did what, one of the researchers flipped a switch without the monkey's knowledge, allowing the computer to direct the cursor via the brain electrodes. The animals could "think" the cursor onto the target just as quickly as they could move it there by hand, the researchers report in the 14 March issue of Nature. Surprisingly, only about six to 30 neurons controlled the motion.
The work demonstrates how the brain can control complex motion with very few neurons, according to neurophysiologist Andrew Schwartz at the Neurosciences Institute in La Jolla, California. Moving a cursor around "is a lot more complicated" than previous efforts, he says. "And they get fairly decent performance."