Children in America are undergoing electric shock treatment in growing numbers. Now known as Electro Convulsive Therapy - or ECT - the controversial treatment is being used on severely autistic children who are prone to violent self-harming behaviour. For the first time, BBC cameras have been given access to film a child being treated using ECT. Our World's, Chris Rogers, meets the parents who say the treatment is improving their children's lives - and the critics who say it is barbaric