Special spectacles help blind people to "see” the world around them. What it does is convert light-dark contrasts into sounds; the lighter an object, the louder the sound. An experienced user can then detect whether he’s "looking” at a plate, for example.
Petra Stoerig from the University of Düsseldorf has examined the brain processes involved. Her research shows that when somebody is only listening, the areas of the brain normally responsible for vision become active.