A monkey with a fingernail-size brain implant moved a cursor on a computer screen just by thinking _ the latest in a series of experiments that have raised hopes that paralyzed people might one day be able to control complex devices with their minds.
While humans have already been implanted with a similar device that allows control of a cursor, the set of thin wires used by the Brown University researchers is less bulky and worked by measuring fewer neurons.
Three rhesus monkeys were given the implants, which were first used to record signals from their motor cortex _ an area of the brain that controls movement _ as they manipulated a joystick with their hands. Then those signals were used to develop a program that enabled one of the monkeys to continue moving the cursor with its brain.
During dozens of trials over several months, the monkey moved the cursor just by thinking and used it to touch dots that appeared on the screen, earning orange juice as a reward, said John Donoghue, chairman of neuroscience at Brown.
The results are promising enough that the device could one day be used on humans, the researchers reported in Thursday's issue of the journal Nature. They would not speculate on how long that might take.
Anything that can be controlled with two- or three-dimensional coordinates can be controlled by similar implants, Donoghue said.
``Anything you can imagine can be engineered. What can you do with point-and-click navigation on the Internet?'' he said.
In 1998, researchers at Emory University in Atlanta reported that a paralyzed man was able to control a cursor with a cone-shaped, glass implant, using it to operate a voice synthesizer that allowed him to communicate.
The key advance in the Brown study is that the researchers were able to use fewer neurons _ between seven and 30 _ to control the cursor, said Sandro Mussa-Ivaldi, a Northwestern University professor and staff member of the Rehabilitation Institute of Chicago.
Mussa-Ivaldi said the glass cone implant is bulkier, but its advantage is that brain cells grow around the glass, holding it in place.
In November, Duke University researchers reported they had wired the brains of monkeys to control robotic arms. When the monkeys reached for food or manipulated a joystick, the robotic arms mimicked those motions.
Duke researcher Miguel Nicolelis, who was involved in the robotic arm research, said similar work has also been done with rodents.
As for transferring the implant technology to humans, ``I always estimate these transfers as somewhere between five and 10 years, but it's very encouraging,'' Nicolelis said. ``It now shows in rodents and in monkeys that this is feasible. It gets us very much on the track to potential applications in humans.''