World and Nation

In a first, experiment links brains of two rats

In an experiment that sounds straight out of a science fiction movie, a Duke neuroscientist has connected the brains of two rats in such a way that when one moves to press a lever, the other one does, too — most of the time.

The neuroscientist, Miguel Nicolelis, known for successfully demonstrating brain-machine connections, like the one in which a monkey controlled a robotic arm with its thoughts, said this was the first time one animal’s brain had been linked to another.

The question, he said, was: “Could we fool the brain? Could we make the brain process signals from another body?”

The answer, he said, was yes.

He and other scientists at Duke, and in Brazil, published the results of the experiment in the journal Scientific Reports. The work received mixed reviews from other scientists, ranging from “amazing” to “very simplistic.”

Much of Nicolelis’ work is directed toward creating a full exoskeleton that a paralyzed person could operate with brain signals. Although this experiment is not directly related, he said, it helps refine the ability to read and translate brain signals, an important part of all prosthetic devices connected to the brain, and an area in which brain science is making great advances.

He also speculated about the future possibility of a biological computer, in which numerous brains are connected, and views this as a small step in that direction.

The experiment involved extensive training for both rats, with water as a reward. One, the so-called encoder rat, learned to press one of two levers, left or right, in response to a light signal over the correct lever. The second, or decoder rat, also learned to press either the left or right lever in response to light, but then went on to respond instead to brain stimulation from his rat partner.

For the experiment, recording electrodes were implanted in the primary motor cortex of the encoder rat and stimulating electrodes in the same area in the decoder rat.

Then, as the encoder responded to the light appearing over one lever or the other, its pattern of brain activity was sent to a computer, which simplified the pattern for transmission to the decoder rat. The signal received by the decoder was not the same as the stimulation it had previously received in training, Nicolelis said. Seven out of 10 times, the decoder rat pressed the right lever.

The researchers reported similar results in other experiments, based on whether the rats sensed a narrow or wide opening with their whiskers. In this case the electrodes were implanted in a different part of the brain, where sensory signals are received.

Ron D. Frostig, a neuroscientist at the University of California, Irvine, said, “I think it’s an amazing paper.” He described it as a “beautiful proof of principle” that information could be transferred from one brain to another in real time — not by mind-reading or telepathy, but a transfer of what might be called the impulse to act.