Monkeys Use Minds to Control Virtual Arms, Reveal New Insights into the Brain

In a Duke University lab, monkeys have learned to control the arm movement of an avatar using only their minds, a new study published in the journal Science Translational Medicine reports.

The researchers recorded nearly 500 neurons from several areas in the cerebral hemispheres of the animals' brains, marking the largest number of neurons ever recorded and reported. This enabled the monkeys to control the virtual arms.

The monkeys were encouraged to place their virtual hands on specific targets, first with the help of a pair of joysticks and then with their brain alone. As their ability to control the arms improved, the monkeys began to exhibit large amounts of plasticity in cortical areas of their brains, suggesting the animals may have been incorporating the avatar arms into their internal image of their own bodies.

Furthermore, cortical regions exhibited specific patterns of neuronal electrical activity that differed based on whether the monkeys used both arms, called bimanual movement, or each arm separately.

Based on these findings, the researchers hypothesize that the large groupings of neurons, rather than individual neurons, are at the basis for everyday motor functions. For this reason, small neuronal samples of the cortex may be inadequate when it comes to controlling complex motor behaviors via a brain-machine system, the scientists suggest.

"When we looked at the properties of individual neurons, or of whole populations of cortical cells, we noticed that simply summing up the neuronal activity correlated to movements of the right and left arms did not allow us to predict what the same individual neurons or neuronal populations would do when both arms were engaged together in a bimanual task," Dr. Miguel Nicolelis, a professor of neurobiology, said in a statement. "This finding points to an emergent brain property -- a non-linear summation -- for when both hands are engaged at once."

These findings will be contributed to an international collaboration focused on designing and building a brain-controlled neuroprosthetic device. Called the Walk Again Project, the endeavour is scheduled to unveil the world's first brain-controlled exoskeleton during the opening ceremony of the 2014 FIFA World Cup.

"Bimanual movements in our daily activities -- from typing on a keyboard to opening a can -- are critically important," Nicolelis said. "Future brain-machine interfaces aimed at restoring mobility in humans will have to incorporate multiple limbs to greatly benefit severely paralyzed patients."