Creating a "superbrain" of connected minds, scientists on Thursday said they had enabled a rat to help a fellow rodent while the animals were a continent apart but connected through brain electrodes.

With electrodes imbedded in its cortex, a rat in a research institute in Natal, Brazil sent signals via the Internet to a counterpart at a university lab in Durham, North Carolina, helping the second animal to get a reward.

The exploit opens up the prospect of linking brains among animals to create an "organic computer," said Brazilian neurobiologist Miguel Nicolelis.

It also helps the quest to empower patients stricken with paralysis or locked-in syndrome, he said.

"We established a functional linkage between two brains. We created a superbrain that comprises two brains," Nicolelis said in a phone interview with AFP.

Published in the journal Scientific Reports, Nicolelis' team gave basic training to thirsty rats, who had to recognise lights and operate a lever to get a reward of water.

They then implanted ultra-fine electrodes in the rats' brains, which were linked by a slender overhead cable to a computer.

In a glass tank in Natal, the first rat was the "encoder," its brain sending out a stream of electrical pulses as it figured out the tricks for getting the reward.

The pulses were sent in real time into the cortex of the second rat, or "decoder," rat, which was facing identical apparatus in a tank in North Carolina.

With these prompts from its chum, the decoder rat swiftly found the reward in turn.

"The pair of animals collaborated to solve a task together," said Nicolelis.

What the second rat received were not thoughts, nor were they images, Nicolelis said.

When the encoder rat achieved various tasks, the peaks in his brain signals were transcribed into a telltale pattern of electronic signals that were received by the decoder rat.

Once the rat recognised the usefulness of these patterns, they became incorporated into its visual and tactile processing.

"The second rat learns to recognise a pattern, a statistical pattern, that describes a decision taken by the first rat. He's creating an association of that pattern with a decision," said Nicolelis.

"He may be feeling a little tactile stimulus, but it's something that we don't know how to describe because we cannot question the subject."

The linkage "suggests we could create a brain net, formed of joined-up brains, all interacting," the scientist said, hastening to stress that such experiments would only be conducted on lab animals, not humans.

"If you connect several animal brains, rat brains or primate brains, you probably could be creating an organic computer that is a non-Turing machine, a machine that doesn't work according to the Turing design of all the digital computers that we know. It would be heuristic, it wouldn't use an algorithm, and it would uses probabilistic decision-making based on organic hardware."

Still unclear is how the decoder animal incorporates the encoder's signals into its mental space, a phenomenon called cortical plasticity.

"We basically show that the decoder animal can incorporate another body as an extension of the map that the animal has in it's own brain," said Nicolelis, adding, though: "We don't know how this is done."

Nicolelis carries out research at Duke University in Durham and at the Edmond and Lily Safra International Institute for Neuroscience of Natal, or ELS-IINN.

A decade ago, he leapt to prominence for pioneering work in having lab monkeys move a robotic arm through brain impulses.

The latest work should help this, he said: "We are learning ways to interact with and send messages to the mammalian brain that will be fundamental for our goals of medical rehabilitation."

His next goal is to have a paraplegic patient give the official kickoff to the 2014 World Cup in Brazil, using a brain-machine interface to activate an artificial limb.