and three monkey brains
can control an avatar
better than any single monkey.
For the first time, a team has networked the brains of multiple animals to form a living computer that can perform tasks and solve problems.
If human brains could be similarly connected, it might give us superhuman problem-solving abilities, and allow us to communicate abstract thoughts and experiences.
These tend to work by converting the brain's electrical activity into signals that a computer can interpret.
Miguel Nicolelis at Duke University Medical Center in Durham, North Carolina, and his colleagues wanted to extend the idea by incorporating multiple brains at once.
The team connected the brains of three monkeys to a computer that controlled an animated screen image representing a robotic arm, placing electrodes into brain areas involved in movement.
By synchronizing their thoughts, the monkeys were able to move the arm to reach a target - at which point the team rewarded them with with juice.
Then the team made things trickier: each monkey could only control the arm in one dimension, for example.
But the monkeys still managed to make the arm reach the target by working together.
He calls the structure a "brainet".
These monkeys were connected only to a computer, not one another, but in a second set of experiments, the team connected the brains of four rats to a computer and to each other.
Each rat had two sets of electrodes implanted in regions of the brain involved in movement control - one to stimulate the brain and another to record its activity.
The team sent electrical pulses to all four rats and rewarded them when they synchronized their brain activity. After 10 training sessions, the rats were able to do this 61 per cent of the time.
This synchronous brain activity can be put to work as a computer to perform tasks like information storage and pattern recognition, says Nicolelis.
This is the way parallel processing works in computing, says Rahwan.
Dividing the computing of a task between multiple brains is similar to sharing computations between multiple processors in modern computers, he says.
Things could get even more interesting once we are able to connect human brains.
All anyone can probably ask of a monkey is to control movement, but we can expect much more from human minds, he says.
A device that allows information transfer between brains could, in theory, allow us to do away with language - which plays the role of a,
The ability to share abstract thoughts could enable us to solve more complex problems.
This might be a way to perform future surgery, says Stocco.
At present, when a team of surgeons is at work, only one will tend to have control of the scalpel at any moment.
Imagine if each member of the team could focus on a particular aspect of the operation and coordinate their brain power to collectively control the procedure.
But there is a chance that such scenarios won't improve on current performance, Stocco says.
Jason Ritt of Boston University agrees.
The ability to share our thoughts and brain power could also leave us vulnerable to new invasions of privacy, warns Rahwan.
It might be possible, for example, for one brain to manipulate others in a network.
There's also a chance that private thoughts might slip through along with ones to be shared, such as your intentions after drinking with someone you invited to the pub, says Nicholas Hatsopoulos at the University of Chicago in Illinois.
In the meantime, Nicolelis, who also develops exoskeletons that help people with spinal cord injuries regain movement, hopes to develop the technology trialed in monkeys for paraplegic people.
He hopes that a more experienced user of a prosthetic limb or wheelchair, for example, might be able to collaborate with a less experienced user to directly train them to control it for themselves.