Neurobiologist Miguel Nicolelis and his colleagues astounded the world in 2003 with the report that they had induced monkeys to manipulate a robotic arm with brain signals. One major question remained: What exactly was going on in the monkeys' brain circuits during this adaptation?
Nicolelis, Mikhail Lebedev, and colleagues have analyzed the data from those earlier experiments in detail and report in a May issue of the journal Neuron that the animals' brains are adapting to treat the arm as if it were their own appendage. "Basically, we were able to show clearly that a large percentage of the neurons become more 'entrained'--that is, their firing becomes more correlated to the operation of the robot arm than to the animal's own arm," says Nicolelis.
While the monkeys were still able to use their own arms, some brain cells formerly used for that control shifted to control of the robotic arm, says Nicolelis. In fact, the researchers found that the animals could flip back and forth between using the natural and artificial appendage. The findings have important philosophical, as well as practical, implications. "This finding," he says, "supports our theory that the brain has extraordinary abilities to adapt to incorporate artificial tools, whether directly controlled by the brain or through the appendages.
"The experiments we have conducted not only represent a proof of concept that such an external device can be directly controlled in a clinical setting; this latest analysis shows that the device is incorporated very intimately as a natural extension of the brain. This is a fundamentally important property if brain-machine interface technology is to have any clinical future."
Arms and the Monkey: From Real to Robotic
October 1, 2005