Two monkeys have learned to control a mechanical arm via tiny sensors in their brains to reach and grab food and deliver it to their mouths according to a report by scientists on Wednesday.
The report was published online in the nature.com journal and is the most advanced demonstration so far of brain-machine interfacing.
Scientists are hoping to eventually use the technology to help people with spinal cord injuries or other paralysing conditions.
Previous experiments have seen nonhuman primates move a mechanical arm with their mind, but this latest experiment goes much further. The monkeys seemed to have adopted the appendage as their own, interacting with real objects in real time and even refining their movements over time. The monkeys’ own arms were restrained during the experiment.
The new report was “important because it’s the most comprehensive study showing how an animal interacts with complex objects, using only brain activity,” said Dr. John P. Donoghue, director of the Institute of Brain Science at Brown University.
The monkeys started out controlling the arm with a joystick in order to gain a feel for the arm. After that, a tiny grid (about the size of a large freckle) was implanted just beneath the monkeys’ skulls. The grid holds 100 electrodes which each connect to a single neuron and sits over a patch of cells on the motor cortex which is known to signal hand and arm movements.
Wires from the grid run out through the skull and to a computer. Though the device could conceivably be wireless, no one has yet demonstrated a workable system.
The computer analysed the firing of each of the 100 motor neurons and translated the patterns into an electronic command which was then sent to the arm. The arm was positioned to be in-line with the monkeys left shoulder as if it were a replacement for the monkey’s own.
It took practice for the monkeys to manipulate the arm. Scientists assisted them at first with biofeedback but after a few days, the monkeys required no help and were successfully using the arm to feed themselves unaided.
On several occasions, a monkey would move the arm back to its mouth to lick the fingers clean as if the mechanical arm were its own.
One of the biggest hurdles scientists must clear if research is to progress is the longevity of the implantable electrode grids. They generally break-down within just a few months.