Do we really use only 10% of our brains?

“Did you know you only use 10% of your brain?” is a recurring factoid about our most mysterious organ.  In fact, studies have shown that pretty much all of it is in use all the time, even when following the plot in Midsummer Murders.  But what about people who have a large percentage of their brain missing?

The most famous example of this was first reported in 2007 in the Lancet.  A 44 year old Frenchman had gone to the hospital complaining about a weakness in his legs when a scan revealed something as shocking to his doctors as it was to him. 

A stent that had been used to treat hydrocephalus, a build-up of fluid on the brain, had been removed when he was 14.  However, over the next 30 years the fluid had continued to slowly build back up, and slowly erode his brain tissue.   What the scan showed was that 90% of his brain had eroded, leaving a thin layer of brain tissue filled with cerebrospinal fluid. 

During that 30 years he’d worked as a civil servant, brought up a family, and been healthy.  So doesn’t that prove that we really only do need 10% of our brains? Actually, what it shows is how adaptable our brains are – a fact shown by our next case.

In 2014 a 24 year old Chinese woman went into hospital reporting nausea and dizziness.  When they took her medical history her doctors noted that she’d always had trouble walking, and had started talking late, at the age of 6. 

When they subsequently took a brain scan they were staggered to find that where her cerebellum should have been there was a space filled by cerebrospinal fluid.  The cerebellum (or ‘little brain’) accounts for half the brain’s neurons and is responsible for balance, voluntary muscle control and movement.

The cerebellum is so vital that being born without it was thought to invariably lead to death at a young age, and the inability to learn to walk or speak.  The fact that this young woman did walk and speak, to the extent that she made her way to the hospital and reported her illness, is not just astounding but still inexplicable. 

These are just two of the cases that show how adaptable the brain is, and how little we truly understand the mechanics behind that.   One thing we can be certain of though – the urban myth that we only use 10% of our brain isn’t just untrue but doesn’t begin to describe how amazing our brains are.

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