Geordi La Forge, the chief engineer of the USS Enterprise-D, could perceive a large swath of electromagnetic spectrum with his wraparound VISOR prosthetic. Now a few rats have received real-life prototypes of these Star Trek props.
Researchers in the lab of brain–machine interface ace Miguel Nicolelis at Duke University Medical Center have outfitted rodents with prosthetics that enable them to "see" and respond to otherwise invisible infrared light. The experiment points toward the prospect, for the moment still a futurist's overheated fantasy, of enhancing humans with a sixth or seventh sense or, perhaps, like a VISOR, an ability to detect a full-spectrum of electromagnetic emanations. It also suggests new paths for neuroscientists to explore the mixing of different sensory inputs and neural proceses to produce new forms of perception.
Reporting February 12 in the online journal Nature Communications, Nicolelis and colleagues recounted how they trained six rats on a standard lab task that taught them to stick their snouts in one of three holes in the side of a chamber when a light in one of the cavities switched on, an action rewarded with a sip of water. (Scientific American is part of Nature Publishing Group.) They then implanted microelectrodes in the rats’ primary sensory cortex, an area that processes sensations of touch. These electrical stimulators were subsequently connected to a forehead-mounted infrared detector. Once the animals were back in the test chamber, the experiment was repeated, with visible lights gradually being replaced by infrared ones in the three holes.
At first the rats appeared somewhat confused, poking the holes in the chamber at random, possibly because the “wrong” portion of the cortex (the part that normally process touch) was interpreting the electrical signals for visual cues. Gradually, their behavior changed and they began to respond more as they had to the visible-spectrum LEDs during training, a sign that their brains were adapting to seeing in the infrared. The same area of the cortex also continued to respond normally to whisker touches as well as the infrared signals. Take a look at this video made with an infrared camera:
"This is a very nice paper that clearly demonstrates the great potential of even the primary sensory cortex, even in a rat, to use completely new information when delivered to the cortex in electrical pulses," says Jon Kaas, a professor of cell and developmental biology at Vanderbilt University and an expert on sensory and motor system organization. "The authors correctly see that this method of delivery can be used to replace lost sensory inputs and to provide new sensory abilities."