Narrator: Graham Young has a very unusual brain. And scientists are so keen to study it that he's regularly flown, expenses paid, all over the world.

Graham Young: It's almost a different life. I live in Chester, and I work in Chester. And I go away doing all this stuff, and it's almost like a— second identity is a bit strong, but it's two different existences.

Narrator: Graham became a hot property for neuroscientists as a result of being hit by a car when he was a child.

Graham Young: I had a road accident when I was eight resulting in some brain damage. So I lost all my vision to the right in both eyes.

Narrator: As far as he was aware, he was completely blind on the right hand side.

Graham Young: I mean, I literally would be walking around town, an eight- or nine year old lad, and I'd actually walk into a lamppost or into a bin. I just didn't see it, and would walk straight into it. And that doesn't happen anymore. And I've just got used to just having a [inaudible] view.

Narrator: 12 years later while he was having his eyes tested in London, they discovered something extraordinary. It turned out Graham's brain could actually process vision on both sides, even though he wasn't aware of it. Graham is a perfect case of a fascinating condition called blindsight.

Professor Larry Weiskrantz: Though most people don't get brain damage in such a way as to satisfy the research scientist, Graham fortunately has damage largely restricted to the visual cortex, and not to the rest of the brain. So that makes it a much more pure case.

Narrator: Graham's road accident destroyed just a small area at the back of his brain. If losing this area caused him to lose awareness of seeing, could this damaged area be the seat of consciousness? Weiskrantz experimented further. He showed Graham moving lights on his blind side.

Graham Young: Right, and aware. Left, and aware. Right—

Narrator: Bizarrely, although Graham says he can't see them, he can guess correctly what direction the dots are moving in.

Graham Young: I am completely unaware of an event occuring in my blind field. And yet in terms of which way it's moved, I get it right 90% of the time. That's a bit strange, isn't it? And I don't know how I do it. Right, and aware.

Professor Larry Weiskrantz: Blindsight is a condition in which one can respond to visual events without being aware of them. OK. Now that means that as you know what the brain damage is, you can start to say something about what areas of the brain are necessary, are critical for awareness.

Narrator: So what is going on inside Graham's brain? Scans suggests that when Graham is responding to the dots, but isn't aware of them, a very primitive visual pathway is active. But when he is actually seeing them, a whole new range of brain regions lights up.

Professor Larry Weiskrantz: We need lots of different areas for consciousness. Just to receive the information isn't sufficient, you have to do something with it for it to become aware. And the regions of the brain that are important for that lie quite far removed from the visual cortex, in the frontal load. Involving those regions of the brain that allow us to communicate the fact that we are conscious, that we are aware.