Another scientific development is bringing modern life closer to the future world envisioned in Star Trek.
Researchers have taken a significant step toward making an implantable machine that could restore and augment vision by bypassing the optic system and training another of the brain’s sensory processing centers to “see.”
A Duke University team has successfully fitted rats with an infrared detector whose electrodes were wired into the part of their brains that sense touch. When the neuroprosthetic device was powered up, the rats felt infrared light as if they were touching it.
The scientists who performed the study say the experiment represents the first time that a brain-machine interface has augmented an adult animal’s senses.
"The philosophy of the field of brain-machine interfaces has until now been to attempt to restore a motor function lost to lesion or damage of the central nervous system," says Eric Thomson, first author of the study published Feb. 12 in the online journal Nature Communications. “This is the first paper in which a neuroprosthetic device was used to augment function—literally enabling a normal animal to acquire a sixth sense.”
Neurobiologist Miguel Nicolelis, a visionary in the field of brain-machine interfaces who leads the group, says their success is a first step to giving animals or people the machine-enabled ability to see in any region of the electromagnetic spectrum. It could also help those whose region of the brain that processes visual information is damaged learn to “see” again through a different information-processing region.
If such technology becomes reality, the world could see devices like the VISOR worn by Star Trek character Geordi La Forge, which allowed the congenitally blind man to see elements of the electromagnetic spectrum.
"We could create devices sensitive to any physical energy," Nicolelis says in an announcement about their success. “It could be magnetic fields, radio waves, or ultrasound. We chose infrared initially because it didn’t interfere with our electrophysiological recordings.”
Such a brain-machine interface could also work to replace other lost senses, like rewiring the sensation of touch for those who have lost it through spinal cord injury.
Training rats to see with their whiskers
In the study, the researchers trained rats to respond to a single visible light that was turned on from a bank of three LEDs. Then microelectrodes, each about a tenth the width of a human hair, were implanted into the cortical region that interprets touch information from the rat’s whiskers. These electrodes were connected to an infrared detector and the LEDs were replaced with ones that emitted infrared light, which mammals cannot see.
The animals eventually learned how to interpret information from the detector that was placed on their heads through the electrodes that stimulated their touch-processing cortical region. They began sweeping their heads back and forth to search for an active infrared signal through the detector and were able to successfully navigate to the active infrared light to receive rewards.
Nicolelis says even though researchers co-opted the part of the rat brain that processed tactile sensations from their whiskers to “feel” infrared light, the animals were still able to sense touch through the whiskers.
"When we recorded signals from the touch cortex of these animals, we found that although the cells had begun responding to infrared light, they continued to respond to whisker touch,” he says. “It was almost like the cortex was dividing itself evenly so that the neurons could process both types of information.”
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