As an added twist, the encoder rat got an additional reward if the decoder rat made the right choice. Since the encoder rat wanted the extra reward, it would try to do the task better. That actually refined the signal in its brain, making it clearer. Once the decoder rat got the stimulation, it made the right choice – giving the first rat the extra reward.
The group even tried the same experiment using an Internet connection with another lab in Brazil. The Internet is rather noisy – signals don't travel perfectly, as anyone who has listened to a Wi-Fi or Skype call can attest. But in this case the results were similar to what they got in the lab when the rats were in close proximity.
But besides being able to transmit signals, Nicolelis found something new after the rats practiced the whisker task for about a month. He looked at the way the first rat's brain responded to its whiskers getting touched and saw a characteristic pattern of activity. Touch the second rat's whiskers and something similar happened, as expected. But after being linked for a period of time the second rat's brain responded to touches on the first rat's whiskers.
This is an important point, Nicolelis said, because it gets to how animals understand their own bodies – how a person knows that the hand is hers rather than someone else's. It's quite possible, he said, that our sense of self -- our model of our bodies -- has something to do with how we interact with other people.
Another question is what the rats are feeling when all this is happening. It's not possible to tell, except by watching their behavior. "It would be interesting to know what the subjective experience is like but the rats cannot tell me," Nicolelis said.
Jean-François Gariépy, post-doctoral researcher at the Center for Cognitive Neuroscience, Duke University, who was not involved in the study, called it an important step, because it links getting information out of the brain – reading it – and getting information into the brain. "It's a big challenge because you want to send signals that are strong enough to be detected by some neurons and you want the signal to be fine enough to mean something, to contain information," he wrote in an email. " connects the two types of [brain-machine interfaces]: those that extract information and those that send information."
But not everyone is convinced that this experiment is a major step. Andrew Schwartz, professor of neurobiology at the University of Pittsburgh who has done extensive research on brain-computer interfaces, said the experiment was a bit too simple because it only involved a binary decision – a yes/ no. "Brain-computer interface technology and demonstrations have moved far beyond this," he said, likening it to a locked-in patient communicating by blinking. "This kind of information could be conveyed by recording from a single neuron in one rat and buzzing electrical current in the receiver rat. If the rat feels the buzz it means yes, no buzz means no."
Nicolelis said the simplicity of the experiment is not a fault. "That is how we start the entire field of brain machine interfaces: with a simple rat experiment that defined a paradigm that Dr. Schwartz has been using for 15 years without any change whatsoever. Simple things are elegant and may lead to big things eventually!"