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Updated 19 August 2020

WATCH | A man blind to numbers has psychologists rethinking how our visual awareness works

A man with a unique neurodegenerative disorder is blind to numbers, despite still being able to read letters and words and do maths in his head.

  • A man with corticobasal syndrome is unable to see numbers, despite being able to do maths and read letters
  • Brain scans show that normal processes of identification are still happening – he's somehow just not aware of the outcomes
  • This single case could provide important insights into visual awareness and its link to our conscious mind

The world is a strange place and can be even weirder for those who don't see it the same way as the rest of us.

From colour blindness to not being able to differentiate between people's faces, there are various ways that people can be "blind" to the world.

For one man, however, a unique neurodegenerative disorder makes him blind to numbers, despite still being able to read letters and words and do mathematics in his head.

His odd condition was recounted in a recently published study in Proceedings of the National Academy of Sciences where psychologists believe that this case could provide new insight into how the human brain perceives our world.

READ | What puts you at high risk of midlife mental decline?

Corticobasal syndrome

Only known as RFS, the engineering geologist in his 60s realised something was wrong when he started having trouble with cognition, temporary vision loss, difficulty walking and losing general control over his motor functions.

He was diagnosed with corticobasal syndrome, a degenerative disease that affects movement and memory by killing brain cells. No one knows what causes it, and while there's medication that can treat the symptoms, there is no cure.

What makes RFS's case interesting is that despite being able to read letters normally, numbers from two to nine just disintegrate into chaos when he tries to read them. He couldn't do maths for his work anymore and struggled to read price tags and hotel numbers. He could, however, still see one and zero, probably due to their similarity to letters.

He was admitted to the Johns Hopkins Hospital in 2011 where the study authors started investigating his case.  

Spaghetti mess

In the video below, RFS is asked to draw what he sees. To a normal brain it looks like an orange 8, but to him, it is just a jumble of lines on an orange background.

RFS also held a physical eight made from foam. On its side as an infinity sign, it looked normal to him, but as soon as he rotated it to stand upright, the whole visual representation as a number fell apart. 

READ MORE | ‘They said my disability was irreversible, but I can do everything’

Brain still sees the numbers

The scientists believe that RFS's brain is still able to see numbers, but that he is somehow not conscious of it.

He was still able to do mathematical equations in his head, so the researchers created a new numerical system for him to use in his daily life. The jumble of lines he sees does not remain consistent, changing every time he looks away, making it difficult for him to distinguish patterns amid the chaos.

As with the foam number – which he was able to see fine when on its side – the scientists posit that everything falls apart as soon as his brain acknowledges something as a number, indicating that numbers and letters may be processed by different parts of the brain.

"These data force us to reconsider the relationship between neural processing and visual awareness; even stimuli processed by a workspace-like cognitive system can remain inaccessible to awareness," according to the psychologists.

Facial recognition

In another test, they hid faces in letters, where RFS was able to see both, but when the faces were hidden in numbers he couldn't see either. However, a brain scan picked up a wavelength associated with detecting faces appearing with the numbers test, indicating his brain was registering what he was seeing, but that he just wasn't able to interpret it. 

This indicates again that his brain processes what he sees just like any other brain, but that his disease is somehow preventing him from being aware of the outcome of that process.

While there are more tests that could help us better understand this condition and how the brain processes visual awareness, RFS's condition has reached a point where it's difficult for him to move or speak, making more tests impossible, despite his willingness to contribute to science.

READ | Eating fish may protect our brains against air pollution

Image credit: Pixabay

 
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