This fact has caused scientists reconsider what it is that makes us conscious. To be conscious is to be aware of ourselves and each other, but despite decades of research, our understanding of it is still basic. If consciousness is based in the brain, how is it possible for a person to lose the majority of their neurons and still be aware of themselves and their surroundings?
Apparently, after visiting the doctor complaining of mild weakness in his left leg, a subsequent brain scan revealed that his skull was mostly filled with fluid, leaving just a thin outer layer of actual brain tissue, with the internal part of his brain almost totally eroded.
It is thought that the majority of the man's brain was slowly destroyed over the course of 30 years by hydrocephalus – the build-up of fluid in the brain. He had been diagnosed with it as an infant and treated with a stent, but it was removed when he was 14 years old leading to the erosion of his brain.
But despite minimal remaining brain tissue and a low IQ of 75, the man wasn't mentally disabled. He was relatively healthy, worked as a civil servant and was married with two children. His case study prompted scientists to question what it takes to survive and challenges our understanding of consciousness.
A cognitive psychologist from the Université Libre de Bruxelles in Belgium, Axel Cleeremans, suggests that it is unlikely that one specific brain region is responsible for consciousness but that the brain learns consciousness over and over again, rather than being born with it, which means that its location can be flexible and can be learnt by different brain regions, explained in a recent lecture on his 'radical plasticity thesis', at the ASSC conference in Buenos Aires.
As the article pointed out, the theory fits in well with recent research that suggests the adult brain is more adaptable than was previously thought – and capable of taking on new roles in case of injury.
It seems that in order to be aware, it is necessary not only simply to know information, but also to know that one knows information. Cleeremans claims that the brain is continually and unconsciously learning to re-describe its own activity to itself, and these descriptions form the basis of conscious experience.
So, what does all that have to do with a man surviving with only 10 percent of his brain? According to Cleeremans, even though the man's remaining brain was tiny, the neurons left over were still able to generate a theory about themselves, which means the man remained conscious of his actions. The story is a striking reminder of what our brains can achieve, even when they're very badly damaged and perhaps provides some hope that it in the future, it might be possible to reverse some of the illnesses that cause neuro-degeneration.