What does a vegetative state mean for the brain?
In a world exclusive, reporter Fergus Walsh followed a group of severely brain injured patients to reveal the revolutionary efforts that are being made to help them communicate with their families and the outside world.
Fergus met Professor Adrian Owen of the University of Western Ontario in Canada to learn what the brain is like when in a vegetative state and what can be done to test consciousness in those patients.
The Mind Reader: Unlocking My Voice- a Panorama Special - will be broadcast on Tuesday 13 November at 22:35 on BBC One. Or catch up later on the BBC iPlayer using the link above.