via Man with rare brain disease unable to ‘see’ numbers – Big Think

Schuberta et al.
  • When a man who was diagnosed with the neurodegenerative disease corticobasal syndrome looks at the numbers 2 through 9, he sees unintelligible squiggly lines.
  • The disability appears to be a peculiar type of metamorphopsia, a visual defect that causes linear objects, like the lines on a grid, to look curvy or rounded.
  • The study has some interesting implications on theories of consciousness.

Someone writes the number 8 on a piece of paper. You look at it, see a shape, but you can’t identify what number it is, or whether it’s a number at all. The markings just look like “spaghetti.”

It sounds strange, but that’s exactly what happened to a man who suffers from a rare neurodegenerative disease called corticobasal syndrome, and now can’t recognize the digits 2 through 9. This disease, caused by damage to the cortex and basal ganglia, often leads to memory problems and difficulty moving, but the inability to identify numbers seems to be a very rare symptom.

In a new study published in Proceedings of the National Academy of Sciences (PNAS), a team of researchers describe how the unique disability sheds light on how the brain processes visual awareness.

The inability to identify numbers posed an immediate puzzle for researchers. If the man (named “RFS” in the paper) can read letters and words, but not numbers, that means his brain must be identifying the numbers — and then selectively discriminating against them.