(Credit: Duke University Medical Center)
Researchers at the Duke University Medical Center have enabled rhesus monkeys to move a pair of arms in a virtual environment using just their brain activity.
Duke has been experimenting with telekinetic monkeys for some time now. In 2000, the university started with an electrode array that allowed owl monkeys to control a prosthetic arm. Earlier this year, we saw a monkey that could control a robot up to 11,000 kilometres away.
Now, a team led by professor of neurobiology Doctor Miguel Nicolelis has taught rhesus monkeys to move both arms of an on-screen avatar just by thinking about it.
The team studied large-scale cortical readings from the monkeys to determine if they could provide sufficient signals to a brain-machine interface (BMI) for accurate bimanual movement — and determined that the neuronal activity for bimanual movement is different to the activity for controlling only one arm at a time. It seems to be that large neuronal ensembles rather than single neurons are responsible for normal motor functions and that small neuronal samples of the cortex do not provide enough information for complex movements via BMI.
"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," Nicolelis said. "This finding points to an emergent brain property, a non-linear summation, for when both hands are engaged at once."
The monkeys were then trained to control two arms in a virtual environment using a pair of joysticks, placing the virtual hands on a variety of objects. Then, the joysticks were taken away, and the monkeys were able to control both arms simultaneously with just their brain activity — without moving their own arms at all.
The study's findings will be incorporated into the Walk Again Project, an international collaborative project to build a brain-controlled walking exoskeleton.
"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 paralysed patients."
The Walk Again Project will debut its first exoskeleton at the opening ceremony of the 2014 FIFA World Cup.