From Kurzweil Accelerating Intelligence:
Researchers have electronically linked the brains of pairs of rats for the first time, enabling them to communicate directly to solve simple behavioral puzzles. They even brain-linked two animals thousands of miles apart — one in Durham, North Carolina and one in Natal, Brazil. The researchers think linking multiple brains could form the first “organic computer.” “Our previous studies with brain-machine interfaces had convinced us that the brain was much more plastic than we had thought,” said Duke University Medical Center neurobiologist Miguel Nicolelis . “In those experiments, the brain was able to adapt easily to accept input from devices outside the body and even learn how to process invisible infrared light generated by an artificial sensor. “So, the question we asked was: if the brain could assimilate signals from artificial sensors, could it also assimilate information input from sensors from a different body?” To find out, the researchers first trained pairs of rats to solve a simple problem — to press the correct lever when an indicator light above the lever switched on, to obtain a sip of water. They next connected the two animals’ brains via arrays of microelectrodes inserted into the area of the cortex that processes touch information.
One animal of the dyad was designated as the “encoder” animal. This animal received a visual cue that informed it which lever to press in exchange for a food pellet. Once this “encoder” rat pressed the right lever, a sample of its brain activity that coded its behavioral decision was translated into a pattern of electrical stimulation that was delivered directly into the brain of the second animal of the dyad, known as the “decoder” animal. The decoder rat had the same types of levers in its chamber, but it did not receive any visual cue indicating which lever it should press to obtain a reward. So to press the correct lever and receive the reward it craved, the decoder rat would have to rely on the cue transmitted from the encoder via the brain-to-brain machine interface. The researchers then conducted trials to determine how well the decoder animal could decipher the brain input from the encoder rat to choose the correct lever. The decoder rat ultimately achieved a maximum success rate of about 70 percent, only slightly below the possible maximum success rate of 78 percent that the researchers had theorized was achievable. This maximum rate was what the researchers found they could achieve when they were transmitting regular electrical signals directly to the decoder rat’s brain that were not generated by the encoder.