A sixty-year-old engineer suffering from a rare neurodegenerative disease presents a symptom that is more than strange. While his brain sees numbers, the latter perceives them as doodles.
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Since 2011, the life of an engineer in his sixties has completely changed. He was diagnosed with neurodegenerative disease rare when he suffered from hand tremors and difficulty walking. Over the years, her illness has led to atrophy of basal ganglia. His symptoms then evolved, taking a rather strange form.
While the patient, nicknamed RFS, is used to working with numbers, now those between 2 and 9 become an incomprehensible scribble for his brain. But he is quite capable of discerning the 0 and the 1, and the letters. Finally, he does not suffer from any problem of vision.
In this video filmed by the scientists, the RLS patient draws his vision, abstract lines, the number eight by copying the model. © Schubert et al. PNAS 2023
His case interested a group of American neuroscientists from Johns Hopkins University. While RFS was performing exercises, the scientists analyzed the activity of his brain with a electroencephalogram (EEG) to figure out what was wrong. They publish their results in the journal PNAS. " The key to this study is to understand what appears to be a paradox: how RFS sees numbers, and only numbers, like spaghetti Explains Teresa Schubert, first author of the study.
Numbers like spaghetti
The scientists asked RFS to copy the number eight, colored in orange. On the filmed images, he begins to draw abstract lines, which change each time he looks at the model again. Finally RFS sees the number eight as a scribble where the color orange acts as a background.
The figures seem to totally confuse the mind of the engineer. Indeed, scientists showed him the image of a known object, such as a violin, with a number on it, the 3. RFS was not able to discern the musical instrument and the number in the image presented.
In this second exercise, the scientists asked the patient to describe the foam figure eight he is holding. If he recognizes the shape of the object, he is unable to describe it in words, or to say that it is the number eight. © Schubert et al. PNAS 2023
A normal EEG
What is happening on the side of the brain waves? On the EEG, everything seems normal. The brain of RFS activates as when it looks at a face alone, when it itself does not see the face or the figure. The result is the same for the figures: if the patient sees a set of lines without a tail or head, his brain activates as if he saw a normal figure.
Thus the brain of this unusual patient is able to understand that he sees a face or a figure when he himself is not aware of it.
According to scientists, the case of RFS demonstrates that visual perception and consciousness are not as closely linked as previously thought. The cognitive system of the brain integrates an image, but requires an additional mechanism so that we are aware of the image that we see.
" There are at least two stages that must occur for us to be aware of seeing something: the brain must detect it and then do additional processing so that the detected thing reaches consciousness. For RFS, the second step does not work when there is a number Explains Teresa M. Schubert.
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