Narration:

One morning, Robert Vickers purchased a large quantity of dry ice, and set about destroying his perfectly healthy left leg

Robert Vickers:

Initially there was a bit of pain. But I guess knowing the outcome, the endorphins or whatever were probably running rampant through my body. And then later in the day when I thought it was just about done, I rang my wife, asked her to come and collect me. My leg was frozen stiff. So she arranged for me to be taken to the hospital. And the next time I woke up it was absolute ecstasy. The leg that I'd wanted to get rid of for all those years was ah just reduced to a, you know, a neat little bandaged stump.

Narration:

By now, you're probably thinking this man is crazy. But the truth is far more interesting and strange. From as early as he could remember, Robert had the strongest feeling his left leg didn't belong.

Robert Vickers:

Around about 5 - 8 years old I started to think about it. And when I could, I'd pretend to be a left leg amputee - you know I'd get a leather belt and ah tie my leg up and put it into my pyjamas. And I could get a certain amount of satisfaction out of pretending for a little while.

Dr Jonica Newby:

You didn't even tell your family?

Robert Vickers:

No.

Narration:

By his teens, the stress of his secret had led to severe depression - and ultimately a suicide attempt.

Dr Jonica Newby:

Did you try to do anything more constructive about this problem with your leg?

Robert Vickers:

Well at times I tried to - you know sort of fatally injure the leg with tourniquets and the likes of that. Dropping the weight of the car on the knee and things like that and but you know the leg was made of tougher stuff than I imagined. And it wasn't until I was about thirty that I thought now get rid of it once and for all.

Narration:

That was the first time he tried dry ice. But the doctors managed to save his leg. What's more, they believed he was mad - and gave him tranquilizers, anti-psychotics, and electroconvulsive shock therapy.

Dr Jonica Newby:

Did you think you were crazy?

Robert Vickers:

Very much so.

Narration:

Until he was confronted with his first similar case a few years ago, psychiatrist Chris Ryan shared that view.

Dr Chris Ryan:

They've been extremely normal people. Just everyday people - bankers, doctors, - not nutty but very distressed by having what they see as an extra leg.

That was the thing that really made me think this isn't a psychiatric illness, it doesn't fit any of the known psychiatric illnesses, Iit must be a problem with the brain in some sort of way.

Narration:

But how could your brain disown your leg?

Dr Jonica Newby:

You'd think the sense of owning your body would be one of the most rock solid things in your life. But apparently, it's amazingly easy to mess with.

Narration:

With the help of these virtual reality goggles, Dr Lorimer Moseley and his team are going to put my awareness into someone else's body ... and being a good sport, Robert has volunteered.

Dr Jonica Newby:

No offence Robert, but I'm not really sure I want to swap bodies with you.

Robert Vickers:

That's alright. I'm not easily offended.

Narration:

Robert is wearing a camera, so I'm seeing what he sees. We're also being touched at exactly the same time. Amazingly quickly, something weird happens.

Scientist:

Now Jonica, on which arm are you feeling the touch.

Dr Jonica Newby:

Well the arm that's in front of me with the black pen, that's gone all hairy.

Narration:

It's completely real - that hairy arm is mine.

Dr Lorimer Moseley:

So your brain is receiving touch information from your arm and visual information from Roberts arm and concludes that vision is winning, vision makes sense here.

Scientist:

OK so now I'll try and give you a disembodied touch.

Dr Jonica Newby:

Oh! Now that's really strange. wow.

Dr Lorimer Moseley:

So if you close your eyes now Jonica and point to where you're feeling that touch - now point ... so you're actually feeling that touch to be half a metre away from your own body.

Dr Jonica Newby:

Wow, so this is a full on out of body experience.

Narration:

How on earth is this possible? Our brains are born with a basic map of a four limbed body outline. But the map needs constant updating from the senses ... touch ... vision ... joint position. These send a live feed to a part of the brain known as the right parietal lobule - which integrates the feeds, and updates the body map.

Dr Lorimer Moseley:

If we start messing with those sensory feeds, we can very easily mess with the body image, and then all of a sudden bang you're outside of your own body.

Narration:

And you don't need fancy virtual reality gizmos to mess with those sensory feeds.

How about a trip to the dentist - remember how the anaesthetic made your lip feel fat? Amputation leads to phantom limbs which often change shape. The sense of owning your body can even expand to accept objects ... so can it shrink to reject bits of you?

Dr Jonica Newby:

OK, I'm back in my own body, but now we're going to try another experiment called the rubber hand illusion.

Narration:

This illusion is so simple, you can do it at home. By stroking my real hand when all I can see is a rubber hand - the fake hand becomes mine - totally.

Dr Lorimer Moseley:

Now tell me what happens when I just cut into your hand ....

Dr Jonica Newby:

scream and look at camera. I thought he was going to cut my fingers off.

Narration:

But more amazing was what happened to my real hand. The scientists have had a thermal camera on it ... measuring temperature.

Dr Lorimer Moseley:

You can see here you've dropped by half a degree here.

Dr Jonica Newby:

Wow.

Dr Lorimer Moseley:

So your hand is now half a degree cooler than it was when we started.

Narration:

This isn't supposed to be possible. When Lorimer published his discovery last year - that the real hand goes cold - it rocked the world of neuro-science.

Dr Lorimer Moseley:

Well, we think that it means that your brain is in a sense neglecting your hand.

Dr Jonica Newby:

Starting to reject it?

Dr Lorimer Moseley:

Well, rejecting is a strong word but it certainly looks like the brain is starting to think well I don't care as much about that over there, I'll allocate less blood to it. I mean that's, I reckon that's an astounding result.

Narration:

And it's given me some insight into how Robert may have felt - but is it really the same?

Dr Jonica Newby:

So Robert; where's your real hand.

Robert Vickers:

It's here right in front of me

Dr Jonica Newby:

Is it anything like you experienced with your leg?

Robert Vickers:

No. (he looks up) No.

Narration:

Unlike this illusion, it seems Roberts problem wasn't a simple case of messed up sensory inputs from the leg.

Robert Vickers:

It felt normal in every way. It looked normal, it behaved normally. There was nothing physically wrong with it except that somehow it didn't belong to me.

Narration:

So what was going on? By 2008, many experts were convinced people like Robert were sane. His condition even had a new name - Body Integrity Identity Disorder or BIID. But the cause was still baffling. A group of neuro-scientists in California were hot on the trail though, with a big clue.

David Brang:

So people with strokes to the back of their head will often start to deny their left arm or leg. Some people actually think that their arms are a communist or that it'll belong to the doctor.

Narration:

These people had strokes to the right parietal lobule - the very bit of the brain that as we saw integrates and maintains the body map. Was this where the problem was? Managing to recruit 4 sufferers of this rare condition - they put them in a brain scanner - and touched the bits of the leg they didn't want. Sure enough the sensory part of the brain lit up - so the feeds were getting in fine as Robert said - but the right parietal lobule did not.

David Brang:

Every subject with BIID that we've tested so far, failed to light up their parietal lobe.

Dr Jonica Newby:

That's amazing.

David Brang:

Oh this is certainly a breakthrough - we were stunned by the results. It's very clear that this is a neurological phenomenon when is always been thought of as a psychological issue.

Narration:

They suspect it means people with BIID have bits missing from their brain's body map.

David Brang:

Just as many of us haven't developed a tail representation, like we used to have in the primordials. These individuals just may only develop a representation for one leg, or one arm. And some people who want both legs amputated, may just have been born without leg representations at all.

Narration:

While it's a huge step forward...

Robert Vickers:

It's beautiful to see that.

Narration

.. unfortunately, it's unlikely brain faults like this can be repaired - though in future they may be prevented if caught early. Meanwhile, having seen the risks BIID sufferers take, Dr Chris Ryan now believes they should have what they want - a safe surgical amputation.

Dr. Chris Ryan

Nobody wants to be chopping off people's legs for no reason but nobody wants people to be standing under train tracks either.

Narration:

Far from being the act of a crazy man, for Robert Vickers, removing his detested leg felt like the only sane thing he could do.

Dr Jonica Newby:

Have you had any regrets since?

Robert Vickers:

Only that I hadn't done it sooner.