In an experiment with science fiction implications, two neuroscientists say they have managed to introduce information directly into the premotor cortex of monkeys. PHOTO CREDIT: Christoph Hitz/NYT
When you drive towards an intersection, the sight of the light turning red will make you step on the brake. This action happens due to a chain of events inside your head. Your eyes relay signals to the visual centres in the back of your brain. After those signals get processed, they travel along a pathway to another region, the premotor cortex, where the brain plans movements.
Signalling the brain
Now, imagine that you had a device implanted in your brain that could shortcut the pathway and 'inject' information straight into your premotor cortex. That may sound like an outtake from The Matrix. But now two neuroscientists at the University of Rochester, USA say they have managed to introduce information directly into the premotor cortex of monkeys. The results of the experiment were recently published in the journal Neuron.
Although the research is preliminary, carried out in just two monkeys, the researchers speculated that further research might lead to brain implants for people with strokes. "You could potentially bypass the damaged areas and deliver stimulation to the premotor cortex," said Kevin A Mazurek, a co-author of the study. "That could be a way to bridge parts of the brain that can no longer communicate."
In order to study the premotor cortex, Kevin and his co-author, Dr Marc H Schieber, trained two rhesus monkeys to play a game. The monkeys sat in front of a panel equipped with a button, a sphere-shaped knob, a cylindrical knob and a T-shaped handle. Each object was ringed by LED lights. If the lights around an object switched on, the monkeys had to reach out their hand to it to get a reward. Each object required a particular action. If the button glowed, the monkeys had to push it. If the sphere glowed, they had to turn it. If the T-shaped handle or cylinder lit up, they had to pull it.
After the monkeys learned how to play the game, Kevin and Marc had them play a wired version. The scientists placed 16 electrodes in each monkey's brain, in the premotor cortex. Each time a ring of lights switched on, the electrodes transmitted a short, faint burst of electricity. The patterns varied according to which object the researchers wanted the monkeys to manipulate.
As the monkeys played more rounds of the game, the rings of light dimmed. At first, the dimming caused the monkeys to make mistakes. But then their performance improved. Eventually the lights went out completely, yet the monkeys were able to use only the signals from the electrodes in their brains to pick the right object and manipulate it for the reward. And they did just as well as with the lights.
This hints that the sensory regions of the brain, which process information from the environment, can be bypassed altogether. The brain can devise a response by receiving information directly, via electrodes. Neurologists have long known that applying electric current to certain parts of the brain can make people involuntarily jerk certain parts of their bodies.
But this is not what the monkeys were experiencing. "The stimulation must be producing some conscious perception," said Paul Cheney, a neurophysiologist at the University of Kansas Medical Centre, USA, who was not involved in the new study. But what exactly is that something? It's hard to say. Marc speculated that the monkeys "might feel something on their skin. Or they might see something."
What makes the finding particularly intriguing is that the signals the scientists delivered into the monkey brains had no underlying connection to the knob, the button, the handle or the cylinder. Once the monkeys started using the signals to grab the right objects, the researchers shuffled them into new assignments. Now different electrodes fired for different objects - and the monkeys quickly learned the new rules.
Marc speculated that someday scientists might be able to use more complex arrays of advanced electrodes to help people who suffer brain damage. Strokes, for instance, can destroy parts of the brain along the pathway from sensory regions to areas where the brain makes decisions and sends out commands to the body.
Implanted electrodes might eavesdrop on neurons in healthy regions, such as the visual cortex, and then forward information into the premotor cortex. "When the computer says, 'You're seeing the red light,' you could say, 'Oh, I know what that means - I'm supposed to put my foot on the brake,'" Marc said. "You take information from one good part of the brain and inject it into an area that tells you what to do."