writes "To make a brain-machine interface, you need a way to capture neurons' electric signals. The most precise and most invasive way uses implants that are stuck in the gray matter. The least precise and least invasive way uses EEG sensors stuck to the scalp. But researchers at Johns Hopkins University say there's a third way that gets the best of both worlds, which is not too invasive and fairly precise. They use ECoG systems, in which a mesh of electrodes is placed under the skull, draped over the surface of the cortex.
They're testing their systems on epilepsy patients, who have these ECoG systems inserted anyway while they're waiting for surgery (the electrodes record the source of their seizures). The researchers are capturing these patients' movement commands from their brains, and using them to control robotic limbs. Someday such a system could be used by amputees to control their prosthetic limbs."Link to Original Source