A volunteer models the TMS device which is worn over the front of the head to stimulate the underlying brain tissue

JOSH VILLA was 26 and driving home after a drink with a friend on 28 August 2005 when his car mounted the kerb and flipped over. Villa was thrown through the windscreen, suffered massive head injuries and fell into a coma.

Almost a year later, there was little sign of improvement. “He would open his eyes, but he was not responsive to any external stimuli in his environment,” says Theresa Pape of the US Department of Veterans Affairs …