Quite often, when we hear about brain-machine interfaces, it’s in the context of returning an ability to people who lack it. People who are unable to speak, for instance, might be able to interface with a machine that could speak for them. Recently, however, scientists at Duke University used such an interface to augment rats with a sort of “sixth sense” – the ability to detect invisible infrared light by sense of touch. The research could have significant implications for the disabled.

In the experiment, the team started by regularly placing the rats in a chamber containing three LED lights, each one located above a small port. The scientists taught the rats that when any of those lights came on (in a random pattern), they would be rewarded with a sip of water if they stuck their nose in the port underneath it.

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Infrared detectors were then attached to the rats’ foreheads, and wired into their brains using an array of stimulating microelectrodes. More specifically, those electrodes were implanted in the cortical region of the brain that processes tactile information from the facial whiskers. The LEDs, meanwhile, were replaced with infrared lights that were too weak to give off any detectable heat – like all mammals, rats are unable to see infrared light.

When the rats were returned to the chamber, their detectors would send their brains a “touch” signal whenever one of the lights illuminated. Those signals would get stronger as the rats got closer to the light source. At first, the animals simply rubbed at their faces when this happened. After about a month, however, they learned to associate those signals with the lights. By sweeping their heads back and forth, they could determine which light was on, and proceed to get water from its port. One of the rats can be seen in action in the video at the bottom of the page.

In order to make sure that the animals weren’t somehow detecting the infrared light in another way, the scientists temporarily disabled their infrared detectors. When they did so, the rats weren’t able to locate the right lights.

What the scientists found particularly intriguing was the fact that while the one region of the rats’ brains was processing input from the infrared detector, it was also still capable of processing regular touch input from the whiskers – it didn’t have to give up one for the other.

Based on this observation, the researchers believe it’s possible that if people lack a sense due to damage to the area of the brain associated with that particular type of sensory input, they may be able to regain that sense by going through another part of the brain. A person who is blind due to damage to their visual cortex, for instance, might be able to see again if their retinal impulses were routed into another cortical region. That other region would still be able to perform its regular function – it would just be doing double duty.

According to neurobiologist Miguel Nicolelis, who led the research and who also led a previous study that allowed monkeys to control a virtual arm and touch and feel virtual objects using only their brain activity, the technology could conceivably also be used to give rats – or humans – the ability to actually see infrared light, among other things. “We could create devices sensitive to any physical energy,” he said. “It could be magnetic fields, radio waves, or ultrasound. We chose infrared initially because it didn't interfere with our electrophysiological recordings.”

A paper on the research was published this week in the journal Nature Communications, and can be accessed via the link below.

Source: Duke University