"And 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."
According to Nicolelis, the analysis revealed that, while the animals were still able to use their own arms, some brain cells formerly used for that control shifted to control of the robotic arm.
"Mikhail's analysis of the brain signals associated with use of the robotic and animals' actual arms revealed that the animal was simultaneously doing one thing with its own arm and something else with the robotic arm," he said. "So, our hypothesis is that the adaptation of brain structures allows the expansion of capability to use an artificial appendage with no loss of function, because the animal can flip back and forth between using the two. Depending on the goal, the animal could use its own arm or the robotic arm, and in some cases both.
"This finding 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" said Nicolelis. "Our brain representations of the body are adaptable enough to incorporate any tools that we create to interact with the environment. This may include a robot appendage, but it may also include using a computer keyboard or a tennis racket. In any such case, the properties of this tool become incorporated into our neuronal 'space'," he said. According to Nicolelis, such a theory of brain adaptability has been controversial.