The brain processes visual information from the eye
Scientists say they have solved the mystery of how a girl with half a brain has near perfect vision in one eye.
The experts were baffled by the 10-year-old girl who was born missing the right side of her brain, whose job it is to map the left field of vision.
Scans revealed the German girl's brain rewired itself during development when she was still in her mother's womb.
The University of Glasgow researchers report the findings in Proceedings of the National Academy of Sciences.
The girl's underdeveloped brain was discovered when, aged three, she underwent an MRI scan after suffering seizures of brief involuntary twitching on her left side.
Apart from the seizures, which were successfully treated, and slight weakness on her left side, the girl has had a normal medical history, attending school and taking part in regular activities.
In other cases, where patients have half of the brain removed to treat severe epilepsy, for example, one field of vision is lost in both eyes, meaning they see only objects on the left or right side of their vision.
In the case of the German girl, her left and right field vision is almost perfect in one eye.
The scan shows how half of the girl's brain is missing
Scans on the girl showed that the retinal nerve fibres carrying visual information from the back of the eye which should have gone to the right hemisphere of the brain diverted to the left.
Dr Lars Muckli, of the university's Centre for Cognitive Neuroimaging, working with German colleagues from Frankfurt, said: "The brain has amazing plasticity but we were quite astonished to see just how well the single hemisphere of the brain in this girl has adapted to compensate for the missing half.
"Despite lacking one hemisphere, the girl has normal psychological function and is perfectly capable of living a normal and fulfilling life. She is witty, charming and intelligent."
He said understanding the powerful algorithms the brain uses to rewire itself could help advance artificial intelligence work.