Mind-reading is powerful stuff, but what about hand-reading? Intricate, three-dimensional hand motions have been "read" from the brain using nothing but scalp electrodes. The achievement brings closer the prospect of thought-controlled prosthetics that do not require brain surgery.

Electroencephalography (EEG), which measures electrical activity through the scalp, was previously considered too insensitive to relay the neural activity involved in complex movements of the hands. Nevertheless, Trent Bradberry and colleagues at the University of Maryland, College Park, thought the idea worth investigating.

The team used EEG to measure the brain activity of five volunteers as they moved their hands in three dimensions, and also recorded the movement detected by motion sensors attached to the volunteers' hands. They then correlated the two sets of readings to create a mathematical model that converts one into the other.

In additional trials, this model allowed Bradberry's team to use the EEG readings to accurately monitor the speed and position of each participant's hand in three dimensions.

If EEG can, contrary to past expectation, be used to monitor complex hand movements, it might also be used to control a prosthetic arm, Bradberry suggests. EEG is less invasive and less expensive than the implanted electrodes, which have previously been used to control robotic arms and computer cursors by thought alone, he says.