That the removal of an entire hemisphere of the brain can be performed with little or no noticable changes in behaviour is a demonstration of the remarkable adaptability of the human brain.
This procedure, known as a hemispherectomy, is a drastic measure taken to treat severe and intractable epilepsy.
If you think it incredible that someone with only half a brain can function normally, then you won’t believe this story from Yahoo News:
A man with an unusually tiny brain managed to live an entirely normal life despite his condition, caused by a fluid buildup in his skull, French researchers reported on Thursday.
Scans of the 44-year-old man’s brain showed that a huge fluid-filled chamber called a ventricle took up most of the room in his skull, leaving little more than a thin sheet of actual brain tissue.
Thanks to Bugs ‘n’ Gas Gal for emailing me a link to the story.