This Man Can’t See Numbers But His Brain Can

August 17, 2020

One man held up a large foam number “8” like an infinity symbol and said the object had two circles and looked to him like a mask. But when he held the foam number upright, the object took off and became a mess of lines.

“He described it as the strangest thing he’d ever seen,” said David Rothlein, a postdoctoral fellow and cognitive scientist at Veterans Affairs Boston Healthcare System. The man, whose initials are RFS, suffers from a rare degenerative brain disease that doesn’t allow him to “see” numbers – on paper, as objects, or even those secretly embedded in scenes.

But there are exceptions. While the numbers 2 through 9 were like a clump of meaningless curves to him, he had no problem seeing the numbers “0” and “1,” according to a new case report, of which Rothlein is a co-author.The case of RFS is more evidence that even in a healthy brain, we’re not always aware of what we’re seeing.

In 2010, RFS suffered a seizure that left him with headaches, difficulty understanding and expressing language, memory loss and temporary vision loss. A few months later, he began experiencing difficulty walking, involuntary muscle spasms and tremors – and his motor symptoms got worse as time went on.

He was diagnosed with a rare degenerative brain disorder called corticopelvic syndrome, which causes problems with movement and speech. According to the study, scans of his brain showed extensive damage and volume loss in the brain, midbrain and cerebellar regions.

He saw problems with the numbers very subtly over a period of weeks, said senior author Michael McCloskey, a professor of cognitive science at Johns Hopkins University.

A bowl of spaghetti.
RFS was introduced to McCloskey by one of his colleagues at Johns Hopkins Hospital, and McCloskey’s team has been studying RFS since 2011, when the man was 60 years old.

As far as the researchers know, RFS was the first patient who couldn’t see the numbers.” He saw something…. . jumbled lines, what he called spaghetti,” McCloskey said.RFS knew he was seeing a number – though he didn’t know which one – simply because he didn’t see this series of jumbled lines and nothing else.

And he can’t remember the different directions of the lines and assign them a number because they change every time he looks elsewhere and back, McCloskey said.” What’s most striking, though, is that it affects numbers rather than other symbols,” he told Live Science. symbols or letters may look similar to numbers; for example, a capital B looks like an 8. but he has no problem seeing letters or other characters.

McCloskey says this means his brain has to make sure that the numbers he’s looking at fall into their own special category (i.e., that they’re numbers) in order for his understanding of them to be scrambled. But the question remains: if he can’t see them, how does he do it?

That his brain doesn’t have a “0” and “1” problem is also “surprising,” McCloskey added. It’s not clear why, but the two numbers may look similar to letters like “O” or “lowercase l,” he said. Or the two numbers may be processed differently than other numbers in the brain because “zero was not invented for quite some time after other numbers were invented,” he said.

To study what happens in the RFS’s brain, the team conducted a number of experiments. They embedded an image of a face into a number to see if RFS saw the face normally, or if it was as messed up as seeing the number. They also hooked him up to an electroencephalogram (EEG) to measure the electrical activity in his brain.RFS said he didn’t even see the face – except for a number – and he didn’t even know anything was there because he was seeing a mess. But according to the EEG, when he was peering at the face in the number, he showed the same brain response as when he reported seeing the face embedded in the letters (without the number).

Similarly, the researchers conducted a word test in which they had RFS press a button every time he saw a specific word, such as “tuba.” When the researchers embedded the word in a number, he didn’t see the word and didn’t press the button.

However, his brain activity was the same whether the target word was alone or embedded inside the number. That means his brain did all the complex processing and knew he was viewing the word and what word it was – but that knowledge never registered in his consciousness, Rothlein said.

So it seems “you can do a lot of work in your brain to know what you’re looking at without any awareness,” McCloskey says.

What we can’t see.
In the RFS brain, McCloskey says, the processing of numbers “happens very normally.” When you’re looking at something, the signal comes from your eyes, but the brain does a lot of work figuring out what the shape is and how it’s separate from other things you’re looking at at the same time. For example, RFS’s brain knows he’s looking at the number 8, but doesn’t make him aware of that knowledge.

“We think RFS’s brain is just like anyone else’s, except that his disease has damaged…. Some…. consciousness that had to happen,” McCloskey said.” He did the brain work to determine what he was looking at, but then realized the extra work it was doing was going wrong.”

Once the brain determines what you’re looking at, one of two things can lead to awareness, which is an ongoing debate in neuroscience, he says. The brain may send signals to areas involved in higher-level processing tasks, such as analyzing and identifying what you’re looking at it, or it may send signals back to areas of the brain involved in lower-level processing functions, where it’s just analyzing the basic elements of the number, such as its shape, McCloskey said.” Either way, that’s where RFS goes wrong,” McCloskey said.

“I can’t say I’ve seen this in any of my cortical basin patients,” said Dr. Timothy Rothman, an associate professor of advanced clinical research at the University of Cambridge and honorary consultant neurologist at Addenbrooke’s Hospital, Cambridge, who was not involved in the study. Although based on the description of his disease, “I would think it’s closer to … . variant [of Alzheimer’s disease],” rather than cortical basin syndrome, it’s hard to distinguish between the two conditions, he said.

Semantic memory is a set of ideas and concepts that we don’t draw from personal experience, but common sense, such as the sounds of letters. Thus, RFS’ inability to see numbers likely stems from problems with verbal and visual integration, “probably tapping into some semantic knowledge access,” Rottman told Live Science in an email. “They did a good job of finding a very specific deficit,” and their explanation for this integration is “very plausible,” he added.

Because RFS’s condition affects much of his brain, researchers were unable to determine where in the brain something was wrong. The team was able to study RFS for several years before his physical illness made it difficult for him to go any further. Physically, his condition worsened, but “mentally, other than not being able to see the numbers, he was the same as before,” McCloskey said.

The researchers created a new set of numbers for him, and he could see them clearly. The disturbance likely “occurs only with numbers in their usual form, because recognizing them involves different brain regions than recognizing numbers in different forms,” such as words or surrogate numbers, McCloskey said.

Rothlein said RFS was an engineer for several years after this problem with numbers came up.” He’s perfectly competent with numbers, so if you let him do math with number words or even Roman numerals, he can do math as well,” he said.” In fact, he was pretty good at math.”