The scans presented here are of a ten year-old German girl who was discovered to be missing the right hemisphere of her brain. Incredibly, she is perfectly normal, except for a history of seizures and a slight weakness on her left side. Attending school with others of her age, it is reported that she is able to study and play sports, just like other kids around her. Of course, the mystery is how is this all possible? To answer the question, University of Glasgow scientists used an fMRI to see where the left eye’s vision is processed. Turns out that the brain’s visual area responsible for the right eye offered up some space for the left.
Normally, the left and right fields of vision are processed and mapped by opposite sides of the brain, but scans on the German girl showed that retinal nerve fibres that should go to the right hemisphere of the brain diverted to the left.
Further, the researchers found that within the visual cortex of the left hemisphere, which creates an internal map of the right field of vision, ‘islands’ had been formed within it to specifically deal with, and map out, the left visual field in the absence of the right hemisphere.
Dr Lars Muckli of the Centre for Cognitive Neuroimaging in the Department of Psychology, who led the study, said: “This study has revealed the surprising flexibility of the brain when it comes to self-organising mechanisms for forming visual maps.
“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."
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.
The scientists believe the right hemisphere of the girl’s brain stopped developing early in the womb and that when the developing optic nerves reached the optic chiasma, the chemical cues that would normally guide the left eye nasal retinal nerve to the right hemisphere were no longer present and so the nerve was drawn to the left.
This implies that there are no molecular repressors to prevent nasal retinal nerve fibres from entering the same hemisphere.
Dr Muckli added: “If we could understand the powerful algorithms the brain uses to rewire itself and extract those algorithms together with the general algorithms that the brain uses to process information, they could be applied to computers and could result in a huge advance in artificial intelligence.”
Press release: Scientists reveal secret of girl with ‘all seeing eye’…