In an incredible feat of neuroscience and communications, researchers at Duke University School of Medicine formed a link between pairs of rats by electronically linking their brains. As such, the rats could exchange motor and tactile information between each other. In one particular case, the experiment showed that a pair of linked rats – one rat on a continent, the other in another continent – could still effectively communicate even though they were spaced by thousands of miles from another.

(c) Katie Zhuang, Nicolelis Labs, Duke University

The findings offer hints to the solid possibility of developing what the researchers call “organic computers“, consisting in sharing information, either motor or tactile, between animals to solve a problem. Just recently, we reported about another breakthrough in the field, from the same Duke University scientists, after a rat was granted a sixth sense. The rat in question had its brain adapted to accept input from devices outside the body and even learn how to process invisible infrared light generated by an artificial sensor. Naturally, a puzzling question overwhelmed the researchers: if the brain can be trained to recognize information from an external sensory input, could it also be able to process information from a foreign body?

Yes it can, according to their findings. The researchers first trained pairs of rats to solve a simple problem, in which they were tasked with pressing the right lever when an indicator light above the lever switched on. If the correct action was taken the rats would be rewarded with a sip of water. With this basic info inserted, the researchers then connected the two rats’ brains  via arrays of microelectrodes inserted into the area of the cortex that processes motor information.

Here’s where the nifty part starts. One of the rats was designated as the encoder, tasked with pressing the right lever when the visual cue was on, just like in the first experiment. However, this time an electrical signal that encoded the brain activity registered during this behavior was sent directly into the brain of the second rat, the decoder. In its chamber, the decoder rat had the same levers, only with no visual cues, so therefore it would have to rely on the cues sent by the encoder rat. The decoder rat had a a maximum success rate of about 70 percent, only slightly below the possible maximum success rate of 78 percent theorized by the researchers.

It’s worth noting – to get a finer picture of just how solid the brain-to-brain interface between the two rates is – that neither of rats would receive a reward if one of them failed to press the correct lever, proving the the communication is two-way.

“We saw that when the decoder rat committed an error, the encoder basically changed both its brain function and behavior to make it easier for its partner to get it right,” said Miguel Nicolelis, M.D., PhD, lead author of the publication and professor of neurobiology at Duke University School of Medicine.

“The encoder improved the signal-to-noise ratio of its brain activity that represented the decision, so the signal became cleaner and easier to detect. And it made a quicker, cleaner decision to choose the correct lever to press. Invariably, when the encoder made those adaptations, the decoder got the right decision more often, so they both got a better reward.”

In a second set of experiments, again pair of rats were trained to distinguish between a narrow or wide opening using their whiskers and signal this by nose-pocking water ports corresponding to each opening. In this test, the  decoder had a success rate of about 65 percent, significantly above expectations.

The two rats don’t even need to be near each other – far from it. To test just how far the transmission limit of the brain-to-brain interface can stretch, the researchers  placed an encoder rat in Brazil, at the Edmond and Lily Safra International Institute of Neuroscience of Natal (ELS-IINN), and transmitted its brain signals over the Internet to a decoder rat in Durham, N.C. The two rats could still communicate between each other, even though they were on different continents.

“So, even though the animals were on different continents, with the resulting noisy transmission and signal delays, they could still communicate,” said Miguel Pais-Vieira, PhD, a postdoctoral fellow and first author of the study. “This tells us that it could be possible to create a workable, network of animal brains distributed in many different locations.”

Nicolelis added, “These experiments demonstrated the ability to establish a sophisticated, direct communication linkage between rat brains, and that the decoder brain is working as a pattern-recognition device. So basically, we are creating an organic computer that solves a puzzle.”

“But in this case, we are not inputting instructions, but rather only a signal that represents a decision made by the encoder, which is transmitted to the decoder’s brain which has to figure out how to solve the puzzle. So, we are creating a single central nervous system made up of two rat brains,” said Nicolelis. He pointed out that, in theory, such a system is not limited to a pair of brains, but instead could include a network of brains, or “brain-net.” Researchers at Duke and at the ELS-IINN are now working on experiments to link multiple animals cooperatively to solve more complex behavioral tasks.

“We cannot predict what kinds of emergent properties would appear when animals begin interacting as part of a brain-net. In theory, you could imagine that a combination of brains could provide solutions that individual brains cannot achieve by themselves,” continued Nicolelis. Such a connection might even mean that one animal would incorporate another’s sense of “self,” he said.

“In fact, our studies of the sensory cortex of the decoder rats in these experiments showed that the decoder’s brain began to represent in its tactile cortex not only its own whiskers, but the encoder rat’s whiskers, too. We detected cortical neurons that responded to both sets of whiskers, which means that the rat created a second representation of a second body on top of its own.” Basic studies of such adaptations could lead to a new field that Nicolelis calls the “neurophysiology of social interaction.”

Findings were published in the journal Scientific Reports.