Researchers at Duke University have managed to develop an experimental prototype that allows rats to "touch" invisible infrared light.
According to the Nature Communications Journal, the researchers fitted the rats with an infrared detector connected to microscopic electrodes that were implanted in the part of their brains that processes tactile information.
The experiment suggests that a human with a damaged visual cortex may ultimately be capable of regaining sight via a device implanted in another region of the brain.
In addition, new sensory input can be interpreted by a region of the brain normally allocated to other tasks without monopolizing the specific function of the brain region.
"We could create devices sensitive to any physical energy," said Prof Nicolelis, from the Duke University Medical Center in Durham, North Carolina. "It could be magnetic fields, radio waves, or ultrasound. We chose infrared initially because it didn't interfere with our electrophysiological recordings."
His colleague Eric Thomson expressed similar sentiments.
"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... 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."
As Nicolelis explains, the researchers used a test chamber with three light sources that could be switched on randomly. They subsequently instructed the rats to choose an active light source by poking their noses into a port while receiving a sip of water as a reward.
Microelectrodes were then implanted into the animals' brains, with the electrodes attached to the infrared detectors. Initially, the rats scratched at their faces, indicating the animals were interpreting the lights as touch.
However, after a month, the animals learned to associate the signal in their brains with the infrared source. They then searched actively for the signal, eventually going on to rack up perfect scores in tracking and identifying the correct location of the invisible light source.
"The meaning is that the brain is not limited by the transducers that exist in our body," Nicolelis confirmed. We can actually allow the brain to incorporate new information from the external world."