He is "very excited by this," Donoghue said.
Ninety-six electrodes, which sit on a 0.2-square-inch (4-square-millimeter) panel, were implanted into the patient's motor cortex, a part of the brain responsible for movement.
The electrode panel is attached by a cord to a penny-size titanium disk on the outside of his skull.
The disk serves as an attachment for wires that connect to a computer, which has been programmed to interpret the messages of the man's firing brain neurons.
Three other patients have since received the implant.
The research is the first evidence that the motor cortex of people with spinal cord injuries can function fairly normally even years after their injuries, according to the researchers.
"When asked to think right or think left, the patients were able to change their neural activity immediately. And their use of the device is seemingly easy," Donoghue said.
"Patients can control the computer cursor and carry on a conversation at the same time, just as we can simultaneously talk and use our computers," Donoghue said.
The researchers used magnetic resonance imaging (MRI) to observe the activity of the brain.
"This is a pilot trial, and we are learning how to make the device work," Donoghue added.
The team noticed an odd drop-off in sensor activity after about six months, probably due to a short circuit, Donoghue says.
The implant of the second patient, a 55-year-old who has been paralyzed since 1999, lost significant signal activity after about 11 months.
(Photos: "Beyond the Brain.")
More to Come
The next step after the pilot study is to make the device wireless, automated, and miniature, Donoghue said.
Elsewhere, other researchers are moving ahead with experiments that involve restoring lost movement in humans.
A team at Stanford University in Palo Alto, California, is attempting to develop an electrode-computer system whose efficiency is closer to that of the human body's system of regulating movement. Their study also appears in tomorrow's Nature.
At Rutgers University in Piscataway, New Jersey, associate professor William Craelius specializes in creating prototypes of bionic arms.
He says perhaps his work and Donoghue's can be tapped to create a hybrid system of human movement.
As far as what Donoghue's team is doing, Craelius said, "It's a very difficult thing. It's working remarkably well."
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