Strokes are a major cause of permanent disability and they affect millions of people every year. The cause is usually a lack of blood flow to one part of the brain, which destroys the affected brain area and robs the victim of the ability to perform whatever tasks that brain area used to process. But an electrical current applied to the head for a short time, even years after a stroke, appears to open up new circuits in the brain, restoring some of the lost abilities, as Oxford University's Heidi Johansen-Berg explained to Chris Smith...