Monkeys treat robot arm as bonus appendage

Only recently though did the researchers discover that the monkey wasn't moving the arm in lieu of its real arm but rather that neurons in the brain had shifted to control the robot.

"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," (Nicolelis) 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...

"From a philosophical point of view, we're saying that the sense of self is not limited to our capability for introspection, our sense of our body limits, and to the experiences we've accumulated," Nicolelis said. "It really incorporates every external device that we use to deal with the environment."

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Journal of Neuroscience