As It Happens

Scientists research man missing 90% of his brain who leads a normal life

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These scans of a French man's brain were published in The Lancet in 2007. Since then, this case has puzzled researchers, including cognitive psychologist Axel Cleeremans. (Feuillet et al/The Lancet)

Show more The case of a man who is still able to function even though most of his brain is missing, has given fuel to radical theories about consciousness. Psychologist Axel Cleeremans, of the Université Libre in Brussels, explains how. 6:28

When a 44-year-old man from France started experiencing weakness in his leg, he went to the hospital. That's when doctors told him he was missing most of his brain. The man's skull was full of liquid, with just a thin layer of brain tissue left. The condition is known as hydrocephalus.

"It is so stunning a case of the brain's ability to adapt." - Cognitive psychologist Axel Cleeremans

"He was living a normal life. He has a family. He works. His IQ was tested at the time of his complaint. This came out to be 84, which is slightly below the normal range … So, this person is not bright — but perfectly, socially apt," explains Axel Cleeremans.

Cleeremans is a cognitive psychologist at the Université Libre in Brussels. When he learned about the case, which was first described in The Lancet in 2007, he saw a medical miracle — but also a major challenge to theories about consciousness.

Brain scans from a 2007 study in The Lancet that looked at a French man missing 90% of his brain. (Feuillet et al/The Lancet)

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Last month, Cleeremans gave a lecture about this extremely rare case at the Association for the Scientific Study of Consciousness conference in Buenos Aires.

Cleeremans spoke with As it Happens guest host Susan Bonner. Here's part of their conversation:

Axel Cleeremans is a cognitive psychologist at the Université Libre in Brussels. (Axel Cleeremans/Twitter)

SUSAN BONNER: It is such a stunning case. I'm wondering, what kind of a larger lesson it offers about our brains?

AXEL CLEEREMANS: One of the lessons is that plasticity is probably more pervasive than we thought it was … It is truly incredible that the brain can continue to function, more or less, within the normal range — with probably many fewer neurons than in a typical brain.

[There's a] second lesson perhaps, if you're interested in consciousness — that is the manner in which the biological activity of the brain produces awareness ... One idea that I'm defending is the idea that awareness depends on the brain's ability to learn.

SB: So, does that mean then that there is not one region of the brain responsible for consciousness?

AC: Precisely. These cases are definitely a challenge for any theory of consciousness that depends on very specific neuro-anatomical assumptions.

For more on this story, take a listen to our full interview.