Human beings are born endowed with five senses, but now researchers at Duke University believe they have developed a sixth one: the ability to see infrared light that's not on the visible spectrum.
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In a study published in the scientific journal Nature Communications, the researchers, working together with scientists from Brazil, reported that they had developed a brain implant that enabled rats to expand their sensory abilities.
Rats' sensory abilities are similar to humans, who have not yet been tested with the implant. It has, however, since been tested on monkeys.
The implant was placed on the rats’ heads and connected to their brains’ somatosensory cortex, which governs the sense of touch, by an electrode. Rats with the implant were able to perceive infrared light at wavelength of 940 nanometers, which is significantly above that of visible light waves, which are 400 to 700 nanometers long.
After 26 days of training, the rats learned to use the new sensation to tell which of three sources of infrared light in their cage had been turned on.
According to the researchers, the implant and the new information it presented to the rats' brain did not affect the areas of the brain used for sight, instead remaining restricted to the touch-specific somatosensory cortex. In essence, they had trained one sense to work instead on behalf of another.
Their findings, the researchers say, could be groundbreaking for people who go blind because it could allow humans who lose their sight to regain it via simulation of a different area of the brain. The study shows that brain areas used to process one specific sense can be programmed to process a different sense, and also that the adult brain can absorb radically new information.
The work of the Duke researchers is one piece of a much larger effort to construct a so-called exoskeleton, a whole-body suit that researchers hope that paralyzed patients could control with their brains and endow them with the ability to walk via infrared sensing. They hope that similar controls could be built into the device and allow the patient to "feel" their limbs and other objects in the environment.
One of the researchers, Dr. Miguel A.L. Nicolelis, called the discovery merely a prelude to another study, set to be reported next month. That study is expected to describe a brain implant that creates a brain-to-brain interface, allowing the minds of two living creatures to communicate with one another without speaking.
In recent years, other prosthetic devices have been developed that control the brain’s cognitive function, memory, decision-making and body movement. But this implant is the first to give animals a completely new sense.