The Man Who Couldn’t See Numbers
In this video, RFS is producing the direct copy response of an orange 8. He first draws black lines and then the orange color. Completed drawing to RFS’s left is his copy of an orange 5. Additional markers and pens were available for him to select the colors which best matched his perception. Credit: Teresa M. Schubert, et. al.
Imagine looking at an elementary school poster that shows the alphabet, and the numbers one through 10. The letters make perfect sense to you, as do the numbers zero and one. But instead of a curvy number “2,” or the straight edges of the number “4,” all you see is a messy tangle of lines. That’s the phenomenon experienced by RFS, a man identified only by his initials for privacy reasons.
In 2011, RFS was diagnosed with a condition called corticobasal syndrome, a progressive neurodegenerative disorder. Normally, that rare condition primarily affects motor circuitry in the brain. However, RFS had an additional symptom—while he was very skilled at math, he became unable to see the written digits 2 through 9. When RFS looked at one of those numbers, he saw in its place something “very strange” that he could only describe as “visual spaghetti.” Even weirder, other images placed on top of or nearby the digits also became completely distorted.
Teresa Schubert and David Rothlein, two scientists who studied RFS’ case as graduate students, discuss what this unusual phenomenon tells us about how the human brain processes incoming visual information.
“I don’t see the shape, but I’m feeling it…this is too strange for words.” In this video, RFS is holding and looking at a large foam eight (from a children’s playmat). He describes both what he is feeling and what he is seeing. Note that his tactile sensation of the form seems intact but he is unable to recognize the digit. Credit: Teresa M. Schubert, et. al.
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Teresa Schubert is a post-doctoral fellow in Psychology at Harvard University in Cambridge, Massachusetts.
David Rothlein is a postdoctoral researcher with the Veterans Affairs Boston Healthcare System in Boston, Massachusetts.
IRA FLATOW: This is “Science Friday.” I’m Ira Flatow. All of us have things that our brains are not good at. For instance, I forget names or mangle them all the time. Sorry if I’ve done it to you. It’s not personal. I promise. But this week, researchers are telling the story of one man with an unusual deficit. He cannot see numbers. “Science Friday’s” Charles Bergquist has more.
CHARLES BERGQUIST: Imagine visiting an elementary school classroom. And along the bulletin board, there’s that colorful poster showing all the letters and numbers. A through Z make perfect sense to you. And zero and one are no problem. But instead of seeing a curvy number two or the straight lines of a number four, all you see is a tangle of lines. That’s the phenomenon experienced by one man, R.F.S. Those are his initials for privacy reasons.
This week, in the proceedings of the National Academy of Sciences, researchers try to explore what’s going on in his brain. How can your brain have some specific shape that is something it cannot see? Joining me now to talk about it are two scientists who both studied R.F.S. during their doctoral work at Johns Hopkins and are both now working on postdocs in the Boston area.
Teresa Schubert is in the Department of Psychology at Harvard. And David Rothlein is at the Veterans Affairs Boston Healthcare System. Welcome to “Science Friday.”
TERESA SCHUBERT: Hi. Thank you.
DAVID ROTHLEIN: Hello.
CHARLES BERGQUIST: So, Teresa, tell us about this gentleman R.F.S. What was his specific deficit here? What was going wrong for R.F.S.
TERESA SCHUBERT: So R.F.S. has been diagnosed with a condition called corticobasal degeneration, which is a very rare brain disease, somewhat similar to Alzheimer’s. In that, slowly, over time, it eats away at your neural tissue. Normally, corticobasal degeneration causes difficulty controlling your muscles and your motor movements, so difficulty walking and chewing.
R.F.S. has those symptoms also that have been progressing over time but then this very strange symptom that we’ve never seen before of when he looks at a digit, it appears to him like spaghetti is the best way he can explain it. It’s just this tangled mess. And he knows it’s a digit because digits are the only things that appear that way. But he has no idea what digit it is. He says it looks truly bizarre.
CHARLES BERGQUIST: How did you come to be working with him? What’s the backstory here?
DAVID ROTHLEIN: R.F.S was seen by a neurologist and neuropsychologist initially at Johns Hopkins Hospital. And the neurologist has a close connection with our advisor and the senior author on this paper, Michael McCloskey. The neurologist knew that Michael McCloskey was really interested in number processing, letter processing, and so referred R.F.S. to Mike to investigate a little bit further. When we saw him trace a B perfectly normal but an eight as a bunch of what he described spaghetti, we knew it was something more than just a problem with digit processing.
CHARLES BERGQUIST: Now, David, it’s not that he can’t do math. He was an engineer apparently.
DAVID ROTHLEIN: Correct. He’s actually quite good at math. And he remained as an engineer even after his digit deficit began. So even though he couldn’t do math using the digits two through nine, zero and one were spared. So before we saw him, he was doing some of his math in binary. He was doing math using roman numerals. He was doing math using number words, basically, anything that didn’t involve those particular forms or characters.
And in fact, we taught him a new set of digits. He was able to learn them very quickly and integrate them in his life. And he continued working as an engineer for a few more years longer than he probably could have if not for those digits.
CHARLES BERGQUIST: So it’s something about the visual form of the digit itself. How is seeing a seven different from flipping it over and seeing an uppercase L?
TERESA SCHUBERT: Yeah. So we know that there is some specialized processing in your brain for processing letters and numbers, also other things like faces, for example. And it seems like, for R.F.S, whenever he’s looking at a shape that gets interpreted as a digit, that’s what causes this weirdness, this warping and distortion, so that he can no longer see it. So for example, if you imagine an eight, it’s just two circles stacked on top of each other.
And if you separate those circles quite a bit, R.F.S. is able to see it as there’s a circle. There’s some blank space. There’s another circle. But as soon as you bring those circles closer and closer together to where it starts looking like an eight to you, it disappears for him. And it becomes this tangled mess. So it’s really about his brain interpreting the shape as a digit that leads it to have this trouble.
CHARLES BERGQUIST: So would it be correct to say that the number sensor in his brain is working, but there’s some kind of noise or interference on the lines leading away from the number sensor?
DAVID ROTHLEIN: Yes, I think that’s a very good way to put it. So the number sensor is it’s looking around the earlier areas of the brain to try to find, am I seeing a digit or am I seeing something else? And when a digit appears, it’s a number two. The number two sensor will raise its hand and say, I see a number two. And then it sends that signal to other parts of the brain, so you know that the name of it is two. You know that it represents the quantity two. But it seems like the output of that is just a bunch of nonsense or crazy distortion that he perceives. And so he can’t interpret what’s being output even though the input is being recognized but not being sent out correctly.
CHARLES BERGQUIST: And in your research, you found that this distortion spaghetti effect extended to other images that were either on top of the digit or placed too closely to the digit?
DAVID ROTHLEIN: Yeah. Because the distortion was so overwhelming, as he describes, we wanted to see if it affected other objects that were placed on top of it. Would they just shine through? Or would they also get distorted with the mess that he perceives with digits? And what we found is that, when we put faces embedded in digits or nearby digits or other objects, he can’t even see that there was an object there. And he can’t certainly interpret that it’s a face or other object.
CHARLES BERGQUIST: I’m unclear on how the number presence blocks awareness of the face.
TERESA SCHUBERT: So the way that we have thought about this and the way that it’s led us into thinking about how your awareness is constructed is you’re always aware of something in a particular place in space. So if you see the number two, you don’t see it floating around. You see a number two in a particular place, 18 inches in front of your face just to the left of the edge of the screen or whatever.
And so we think that the reason that R.F.S can’t see these faces, for example, when they’re embedded within a digit is the part of his brain that’s constructing this awareness of what he’s seeing has to take information of everything in that place. And because one of the things in that place is this digit which is giving these distorted signals, that’s distorting everything in that same location. And that’s why if you present a digit on one side of the screen and a face on the far other side of the screen or somewhere else entirely, he can still see that face fine. It’s only when they’re in the same location and his awareness is trying to assign to that location face but also this weird distorted thing that that distortion basically wins out, and that’s all he sees in that location.
CHARLES BERGQUIST: When we see something, is there some kind of dispatcher in the brain that says, this thing that you’re seeing is a face, we’ll send it to the face processing part? Or does the visual information wash over the entire brain at once and only the correct parts are keyed to respond to the input?
TERESA SCHUBERT: I think that second explanation is probably closest to the way we think of the visual parts of the brain as working. So all of this visual input is coming into your eyes. And there are specialized areas of the brain for processing and recognizing faces and digits and letters.
And so when there happens to be a digit in what you’re looking at, that digit area becomes active. And then that area, as David was just saying, is going to pass that information. Oh, I’ve detected a two. Or the face area saying, oh, I’ve detected a face, is going to pass that information on. And in order for you to actually become aware of seeing the two or seeing the face, that information has to get passed on correctly.
CHARLES BERGQUIST: So if you do an MRI or some other kind of brain scan on him, can you point to a specific part of the brain and say, ah, I see this physical flaw. That is where things are breaking down for R.F.S.
DAVID ROTHLEIN: No. We cannot because he has– because it’s a degenerative condition, it affects lots of areas in the brain. So basically, his brain, if you look at his scan, it’s the spaces between. There’s the folds and hills of the brain. The spaces between the different hills are much larger. And that’s because there’s atrophy of the gray matter that comes with degenerative conditions. And so while his whole brain looks a little more atrophied as a whole, we can’t point to a single location and say, oh, there is a lesion there. There’s a hole there. That is, at least, the source of his dysfunction.
CHARLES BERGQUIST: People talk about how marvelously adaptable the brain is. And there are these stories of somebody who lost one form of perception, makes up for it in another area. Why isn’t his brain able to shift this number sensing capability off on to another area of the brain or adapt to deal with this degeneration?
TERESA SCHUBERT: So I think in cases of degeneration, unfortunately, plasticity is a lot more limited. So certainly, after someone has had a stroke, especially if that’s relatively early in their life, but even adults, people in their 60s and 70s who have a stroke can often recover an incredible amount of function. And their brain undergoes some reorganization.
With degenerative conditions, it’s much harder because any place that the brain may try and reorganize or send functions to a new area might be the next place that’s knocked out by the degeneration. But also for R.F.S., in one way, he was able to overcome the deficit. So Mike developed for him this set of surrogate digit symbols, which are just other ways of drawing the digits.
They look nothing like the normal digits. They’re made completely of straight lines. And they have a very systematic relationship. If it has two horizontal lines, it’s a six. If it has three horizontal lines, it’s an eight. I don’t quite remember the system.
But R.F.S. was able to learn those. And he actually uses those every day as his new digits. So this new way of representing the digits has given him a way to continue jotting down notes and doing math problems but also indicates that those are preserved in his brain. And his brain isn’t distorting those as well as the original digit.
CHARLES BERGQUIST: Right. Are there other people with this deficit, selectively unable to see specific things?
DAVID ROTHLEIN: There’s certainly plenty of cases where there’s individuals who cannot see certain categories of objects. So there’s people who, after a lesion to the brain, might have trouble seeing or identifying faces, identifying words. So these what we call agnosias or difficulty recognizing things exist.
However, what makes R.F.S.’s case unique is that he sees something, but it doesn’t look anything like what is hitting his eyes essentially. It’s getting to his brain and then distorting. So it looks very different. So what we call that is a metamorphopsia. And there’s only other case of category specific metamorphopsias occur actually with faces, where some people, after stroke or during seizures, might report that faces or half of the face will appear like it’s melting, for example.
CHARLES BERGQUIST: So this is not just, oh, I have trouble with faces. I have trouble recognizing people. It’s whatever that person has on top of their shoulders does not look like a face to me.
TERESA SCHUBERT: That’s right.
DAVID ROTHLEIN: Or it looks like a highly distorted face.
CHARLES BERGQUIST: Interesting. I’m Charles Bergquist. You’re listening to “Science Friday” from WNYC Studios. In case you’re just joining us, I’m talking with Teresa Schubert and David Rothlein about the case of R.F.S., a gentleman who was unable to see the digits two through nine.
There are tons of theories about how the brain works. Does this study point to any one of those sets of theories more or less than another? Or does it exclude things? OK, well, that’s clearly not how the brain works.
TERESA SCHUBERT: It certainly excludes a theory that you might have just as someone living with a brain about the way your brain works, which is the idea that, when you open your eyes, they function like a video camera or they are taking snapshots of the world. And everything that comes in through your eyes, you’re going to see. That’s clearly not the case for R.F.S.
This digit information is coming in through his eyes. And it’s being detected as a digit, which we know. Because otherwise, everything would be distorted. It wouldn’t be selective just to digits.
But that information isn’t becoming something that he can see. So there has to be at least two, possibly many more stages, that allow you to first detect something. But that, on its own, is not enough for you to see it, for you to actually become aware of, ah, there’s a two there. There have to be stages after that that process that information into a way that it actually becomes part of your conscious awareness of what you’re seeing in the world.
CHARLES BERGQUIST: So a lot of medical research is based on these huge studies of thousands or hundreds of thousands of people to get some big data trend. And here, you’re looking at one man. How much can you tell about the wider world from just looking at one guy?
DAVID ROTHLEIN: So I think that’s a really good question. The trend tends to be we want to have larger samples of studies. We want to have more people because we want to generalize these findings. And for many kinds of findings and questions, this is true. If we’re giving a medicine to people who have the cold, we want to make sure that it works not just for one person but works for everybody.
However, when you’re addressing theories about how the mind and brain work, I think looking at a single individual could be the most informative because the kinds of statements that are theories, which is, for example, consciousness works this way. If you find one case where it doesn’t work that way, then that theory needs to be expanded or at least reconciled with your single case. And so I think they can, in fact, be very informative.
CHARLES BERGQUIST: Teresa Schubert is a postdoctoral fellow in psychology at Harvard University in Cambridge, Massachusetts. And David Rothlein is a postdoctoral researcher at the Veterans Affairs Boston Healthcare System in Boston. Thanks to both of you for talking to me today.
TERESA SCHUBERT: Thank you.
DAVID ROTHLEIN: Thank you very much.
CHARLES BERGQUIST: For “Science Friday,” I’m Charles Bergquist.