Ed Yong over at National Geographic's Not Exactly Rocket Science:
In a lab at Harvard Medical School, a man is using his mind to wag a rat’s tail. To send his command, he merely glances at a strobe light flickering on a computer screen, and a set of electrodes stuck to his scalp detects the activity triggered in his brain. A computer processes and relays the electrodes’ signal to an ultrasound machine poised over the rat’s head. The machine delivers a train of low-energy ultrasound pulses into the rat’s brain, stimulating its motor cortex – the area that governs its movements. The pulses are aimed purposely at a rice-grain-sized area that controls the rat’s tail. It starts to wag.
This link-up is the brainchild of Seung-Schik Yoo, and it works more than 94% of the time. Whenever a human looks at the flickering lights, the rat’s tail almost always starts to wag just over a second later. The connection between them is undeniably simple. The volunteer is basically flicking a switch in the rat’s brain between two positions – move tail, and don’t move tail. But it is still an impressive early example of something we will see more of in coming years – a way to connect between two living brains.
Science-fiction is full of similar (if more flamboyant) brain-to-brain links. From the Jedi knights of Star Wars to various characters in the X-Men comics, popular culture abounds with telepathic characters that can read minds and transmit their thoughts without any direct physical contact or the use of their senses. There’s no evidence that any of us mere mortals share the same ability, but as Yoo’s study shows, technology is edging us closer in that direction. The question is: how far can we recreate telepathy using electronics? A human wagging a rat’s tail is one thing. Will we ever get to the point where we can share speech or emotions or memories?