Brain-computer interfaces (BCI) have been successfully used to both read signals produced by the brain to control external devices, as well as to deliver signals to the organ to create sensation. Having a healthy dose of curiosity not impeded by fears of Frankensteinism, a team from Duke University wired the brains of two rats together using identical BCI’s to see whether one rat can adapt and learn from signals coming from the other rat.
The two rats were first taught to seek water under the spot where a light is lit. Once the rats were comfortable with the task and placed in identical cages, the researchers turned on the brain-brain interface and only had one of the rats receive light signals telling it where the water is. Amazingly, the other rat, not knowing on its own where the water is, followed his partner’s cues and fairly consistently found his source of refreshment.
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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 based on success rates of sending signals directly to the decoder rat’s brain.
Importantly, the communication provided by this brain-to-brain interface was two-way. For instance, the encoder rat did not receive a full reward if the decoder rat made a wrong choice. The result of this peculiar contingency, said Nicolelis, led to the establishment of a “behavioral collaboration” between the pair of rats.
“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,” Nicolelis said. “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, the researchers trained pairs of rats to distinguish between a narrow or wide opening using their whiskers. If the opening was narrow, they were taught to nose-poke a water port on the left side of the chamber to receive a reward; for a wide opening, they had to poke a port on the right side.
The researchers then divided the rats into encoders and decoders. The decoders were trained to associate stimulation pulses with the left reward poke as the correct choice, and an absence of pulses with the right reward poke as correct. During trials in which the encoder detected the opening width and transmitted the choice to the decoder, the decoder had a success rate of about 65 percent, significantly above chance.
Study in Scientific Reports: A Brain-to-Brain Interface for Real-Time Sharing of Sensorimotor Information