“Although real-life brain-controlled prosthetics that enable a person to, say, pick up a pencil continue to improve for amputees, limbs that can actually feel touch sensations have remained a challenge. Now, by implanting electrodes into both the motor and the sensory areas of the brain, researchers have created a virtual prosthetic hand that monkeys control using only their minds, and that enables them to feel virtual textures.
Neuroscientist Miguel Nicolelis of Duke University in Durham, N.C., whose group has been developing so-called brain-machine interfaces, says that one of the pitfalls in these systems is that “no one’s been able to close the loop” between controlling a limb and feeling a physical touch. So he and a group of researchers decided to create a “brain-machine-brain” interface using a virtual system.
The researchers implanted two sets of tiny electrodes into a monkey’s brain: one set in the motor control center, and the other in the part of the somatosensory cortex that processes the sensation of physical touch from the left hand. Using the first set, the monkey could control a virtual monkey arm on a computer screen and sweep the hand over virtual disks with different “textures.” Meanwhile, the second set of electrodes fed a series of electrical pulses into the touch center of its brain.
A low frequency of pulses indicated a rough texture, whereas high frequency indicated a fine texture (see video), and the monkeys quickly learned to tell the difference. By giving the monkey rewards when it identified the right texture, the researchers discovered that it took as few as four training sessions for the animal to consistently distinguish the textures from one another, even when the researchers switched the order of the visually identical disks on the screen. The researchers then implanted the electrodes into the sensory region that receives tactile sensations from the foot in a different monkey; this monkey, too, acted as if the virtual appendage (in this case, the foot) was its own, moving it to correctly identify the textures, the team reports online today in Nature.”