A man who was found to be clinically blind, has astonished scientists by retaining elements of his sight.
The patient was diagnosed as clinically blind after suffering two consecutive strokes that destroyed the visual cortex of his brain and caused him to lose his sight.
The first stroke damaged his hemisphere and visual cortex, while the second stroke, five weeks later caused damage to the other hemispheres.
After the strokes, an assessment of his brain functions found he was blind and whlie this is not uncommon, he shocked doctors by retaining his ability to register the emotions on someone’s face.
Known as selective bilateral occipital damage, the patient responded with appropriate facial expressions, despite not consciously being able to see.
The man’s condition attracted scientists, specially Neuroscientist Beatrice de Gelder who affiliated with Tilburg University, Netherlands and Massachusetts General Hospital in Boston. They began studying his condition and organised a simple test to judge his abilities.
This included an obstacle course, where objects such as boxes and chairs were arranged in a hallway. While the patient was initially reluctant to take part, because he walked with assistance and a cane, he did eventually agreed to take part.
The results were, the scientists claimed, “astonishing” as the man managed to navigate his way down the hall without interacting with any of the obstacles.
“One was a typical paper basket; one was a stack of books,” says de Gelder. “They all had different shapes and sizes.” – Source NPR
She then told TN to walk down the hall.
“We didn’t give him information about obstacles or anything. So he was not aware that there were obstacles.” – Source NPR
“He never touched any of it. We were like totally amazed,” says de Gelder, who reports her finding in the journal Current Biology. You can see this test by clicking on the video link above.
So could the patient see, while still technically being blind?
The condition, brought on by the stroke, was diagnosed as “blindsight” and meant while his visual cortex had been damaged, his eyes remained functional.
It meant the patient could gather information from around his environment, but no longer have the visual cortex to process and interpret it.
In a sense, he retained his “sight” but it became subconscious.
While he doesn’t have a visual picture, he is able to retain awareness of the world around him.
The incredibly rare condition has been previously observed in monkeys, this is the first recorded case in humans.
Video of The Experiment
