Dr. Eden and her colleagues were the first to apply functional magnetic resonance imaging (fMRI) to the study of dyslexia. She continues to investigate the neural representations of sensory processing and reading and how these may be different in individuals with learning disabilities or altered early sensory experience.
Dr. Eden appeared in our PBS Launching Young Readers show, Reading and the Brain.
What do we know about what’s different in the brain of a person with dyslexia?
There are differences in the brains of people with dyslexia that we can measure with brain imaging. And it’s believed that many of those differences already are present at birth. And other differences may be there because of them not having the same kind of reading experience as a person who doesn’t have dyslexia. And we measure these differences primarily with magnetic resonance imaging. And the differences that we see are reflected in the different kinds of analysis we can do with MRI.
And so we have people inside the scanner to say a reading task or a sound deletion task, and we look at: how does the activity in the brain differ? And that activity is measured locally in the brain. Which areas differ? But also people use the data to look at the amount of correlation across those different areas, so it’s sort of a functional connectivity. And you can take any of these measures and try to incorporate them all together to get a really good understanding of how does the brain in people with dyslexia differ in terms of the anatomy, the function and as a network how all these areas fit together. And the areas that we’re talking about are mainly areas involved in reading or in skills that we know support reading.
The finding that most people agree on is that when you look at the left hemisphere in studies of groups of people with dyslexia and people who do not have dyslexia — and I emphasize it’s really group studies — is that there is differences in the anatomy, primarily in the left hemisphere in regions that are known to serve language and written language. And that’s also where we see differences in activity.
So when those participants are doing a task that involves reading or something like manipulating phonemes, they may under-activate those parts of the brain. They’re not using them quite to the same level even though they were actually doing the tasks. So it’s not just that they’re just not doing the tasks and therefore the brain isn’t active. They just aren’t engaging those areas quite so much, particularly an area in the back of the brain in the areas around the temple and parietal cortex that are involved in helping us understand how words are made up of sounds and how we map sounds to print, but also an area at the bottom of the temporal lobe that’s involved in visual word form recognition.
This is an area that we use when we read and we recognize words by sight. It’s an area that a skilled reader trains up. That’s how we become automatic readers. And that’s also one area that’s not activated the same way in people who have dyslexia compared to those who do not.
Can an MRI diagnose dyslexia in an individual child?
We have a lot of inquiries from parents who really would like us to do an MRI on their child because they feel their child is a struggling reader and the school isn’t recognizing it. And they’re hoping that the brain scan will show it. But that’s not how we use the brain scans. We really do look at data for a group. We do look at individual variation, but we wouldn’t be able to go in and look at one scan and say, “This is a child who has dyslexia.”
Which came first? The reading difficulty or the brain differences?
One of the things that’s made dyslexia difficult to study is that even though it’s primarily a reading difficulty — and that’s how people recognize it, as difficulty with reading single words because of the struggles of decoding those words — the manifestations of dyslexia have been described to be quite varied. People have talked about not just difficulties in reading but differences in motor performance and visual tasks and so on.
And so people have often wondered: why are there these different behavioral manifestations? Some of these could be part of the dyslexia even though they’re not causing the reading difficulties, and some of them may be the consequence of not learning to read. And that’s also where brain imaging is helpful as a tool to begin to help arbitrate between different theoretical frameworks. And we have found, for example, that the visual system in some areas that aren’t directly involved in reading are also altered.
But that’s not the part that’s contributing to the reading problem. But it seems to change as a function of whether we’re skilled readers or not. And it may have something to do with the fact that as humans we learn to read. It’s a uniquely human skill. It requires some combination of things that we do including a lot of eye movement and very carefully controlled saccadic eye movement across the letters as we scan them.
And that’s not necessarily how our brain was expecting us to go about leading our daily life. And so it’s not unexpected that when we look at typical readers, what we see as a typical person is really a person whose brain has changed in response to having undergone years of learning how to read. And that’s how the brain has become organized. So for people who don’t read as much because of their dyslexia, we may not see some of those systems the way we see it in typical readers. And we have to be careful how we interpret them. Is it the dyslexia that’s causing that or is it a consequence of not reading as much?
What have we learned about functional specialization in the brain?
Well, I think what’s really helped in our field is this intense interest in how the brain is organized, how it’s functionally specialized and recognizing that there are areas like the visual word form area that’s really part of the object recognition pathway and it’s been fine-tuned to responding to words — and understanding that that’s a part of the process of becoming a skilled reader, and that that is something that doesn’t happen in people with dyslexia and it doesn’t happen in people who are illiterate either.
How does the brain change with a successful dyslexia intervention?
I think what people are showing with the brain imaging is that there’s a lot of convergence in terms of where the brains of people with dyslexia differ. And even if you’re in countries using different languages and even using different writing systems, there are some underlying common differences that we see. I think where it gets really more interesting and somewhat more complicated is when you look at interventions.
We are very interested in seeing: what is the brain correlate of a successful intervention? What happens to people with dyslexia when they get better at reading? Then what kicks in? Is it the same brain areas that all readers use? Is it different? Is it a compensatory strategy? Do they just abandon the areas that they would normally use? Was it a combination of both trying to use more of the areas that they weren’t using before with additional areas that kick in?
And that’s where I think the research is really very interesting because again, it speaks for the nature of the reading difficulties. And why are the areas that now chime in: why those? What is it that they do to help us become skilled readers? And it’s sort of a combination of those two, which is what we see. And I think, in part, that will also be a function of the nature of the intervention. People use very different types of interventions to try and help kids read.
Really the ones that we subscribe by are the ones that address decoding, that are very explicit and very direct. But it’ll be interesting to see how not just the outcome changes in terms of their reading ability but also the nature of the differences in the brain depending on the kind of instruction, perhaps depending on the kind of intensity of instruction, how many hours or if you do it over a longer period. And those are all questions that haven’t been asked yet by science, but they will be soon.
I think the field is at a point where we see convergence in terms of that there are some areas that do seem to actually kick in following the intervention, but there’s also compensation that people report right hemisphere changes that seem to speak to compensation. The nitty-gritty of these are somewhat different between studies, and that could be explained by the different tasks that people are doing in the scan and the different interventions that are being used.
And I think more research there of course will be helpful, but I think there’s a general understanding that we can identify changes that follow interventions. And I think it will be interesting to look at those in different languages and in different writing systems and so on.
Teachers: You are changing brains
I always say to teachers, “You are changing the brains of all children.” As you learn to read, you’re changing your brain. And if you struggle to become a skilled reader and then have intensive intervention, you again have to change your brain in order to produce that behavior. And quite how people go about that is interesting because it’s not identical for everybody. And for children with dyslexia it’s under very different circumstances, difficult circumstances.
Dyslexia is highly heritable
Dyslexia is highly heritable. It runs in families. If you have dyslexia, the chance of your child having dyslexia are between forty and fifty percent, and that’s an important thing to know. I think it’s sort of surprising how few people do know that because when you want to know who’s at risk, you can give children pencil and paper tests and see: how good are they at understanding the sounds that make up words? How good are they at naming their letters?
But a strong predictor already is just knowing who in your family has struggled with learning to read, and unfortunately, when kids go to school, we don’t have that question on the piece of paper that we fill out as parents that asks many good questions like, “Does your child have allergies?” and so on. But the question that’s missing there should be: do you have learning differences in your family? Because if there are, then it’s likely to stay in their family; and they can be much more pro-active early on to try and get their child the help they need as early as possible.
For individuals with dyslexia, how similar are the differences in brain functioning and structure compared to individuals without dyslexia?
We study groups of participants in part because we need the statistical power. But we look at variance within the group as well. And to what degree children are the same as each other or different from one another — that’s a really good question because when you measure their performance on skills behaviorally, there’s some differences. They’re not all the same. They have some key features.
They have difficulty with reading at the word level. They have difficulty with decoding. Most of the time they have difficulty with phonemic awareness. But then they vary. Some have tremendous difficulties with other things like rapidly naming objects, with working memory. Some may have some more severe problems with comprehension that is influenced by their poor reading. And there is some variability. Even two children with dyslexia in the same family may not be identical.
And so, of course, from the brain perspective, people are beginning to ask that same question, which is: are there these differences? And the other thing I think the field is beginning to understand is that children with dyslexia, for example, are at higher risk for also having difficulty with math. And those go together more often, and so the occurrence of math difficulties is higher amongst the population with dyslexia than those without.
And we think of them as very separate because they seem to be very different tasks, but in reality they do share some common origins. And it may be that you are identified because of your reading difficulties; and maybe your math appears to be fine, but actually it’s just a little lower than would be considered fine. And it’s there and it’s a problem, but it becomes — it’s undiagnosed. And I think it’s easier for people to spot reading difficulties than to spot difficulties in arithmetic and so on.
And so I think the nature of how different or similar people with dyslexia are from each other also sort of depends on these other difficulties that they have. And people do start thinking of them now in terms of a continuum where it may be that you have some difficulties in both, but one may be more extreme than the other.
How does ADHD correlate with dyslexia?
This is the other thing, is that the number of children with ADHD is higher amongst a population of dyslexics. And so just like math, you just see more co-occurrence of these learning-related difficulties, things that impede your ability to do well in school. And the question is: when it comes to treatment how do you address those? Right? So the treatment of ADHD is really quite different than the treatment for reading or arithmetic.
Now some of the things to help you to become better at reading may also help you to become better with doing arithmetic. From studies where typically reading children have been followed longitudinally, phonemic awareness predicts not only reading outcome but also math outcome. Those things do hang together. How ADHD and dyslexia hang together is more complicated, but again you have to understand the child as a whole to think about what are the sorts of things this child needs to address each of those separate problems in a way that is sort of holistic and helps them to become a better learner.
Might brain imaging predict who will respond well to an intervention?
As it turns out, the brain is very malleable to begin with to learning. That’s why our kids learn to read. When it comes to intervention, again, you’re heightening the intensity of the instructions, and the brain does change following intensive reading intervention. And, unfortunately, there are some children with dyslexia who really even under the best of circumstances really have a very hard time learning to read.
What we don’t quite know about yet is who those kids are and what that means at the level of the brain, but that’s something that’s being investigated, which is: who are the kids that respond well to interventions? And who are the kids that really don’t respond that well and are harder to remediate? And the other thing that people are looking at brain imaging for, from a research perspective, not as a way to use in any practical way, but: what is it that the brain scan looks like before you begin the intervention when you consider it in the context of the benefits that were reaped following the intervention?
So is there something about the activity in the brain that predicts who is going to do well, who is going to make the biggest gains following the intervention? And the way you can think of that is sort of a brain readiness. If there are certain structures that seem to be active during reading and even more so if then the reading improves because of the intervention, that tells us something about that brain structure and its role in reading and reading disability.
Can imaging tell us anything about what interventions a child could benefit from?
When we do our studies as a group of participants, we can see which brain areas signal later success. Do we use that to structure an individual child’s intervention? No. A person with good clinical experience will do that without a brain scan because they know, you know, any person who does that kind of work well should be looking at the child’s skillsets across a range of skills, look at where they have strengths and weaknesses, and then come up with a suggestion for an avenue for treatment that really would benefit that child. I don’t see the imaging as contributing to that. That’s really the job of a good educator and clinician.
I think you want to really understand the kind of individual variances that we see in children. I think there are some children that you can see from their profile it’s going to be a difficult and long journey for them to learn to read. That doesn’t mean you don’t try. And I think what we just need to become better at is understanding what works for what child. I think the imaging can contribute to that a little bit in terms of from the research side helping us understand: which are the brain areas that change, and why do they change and in whom? But in the end it’s still a skilled clinician who is the person who will best be able to identify what treatment to provide.
How does brain imaging reveal the impact of educators’ work?
I think many educators who work with students who have dyslexia really can make the connection to the findings that come out of science. I see it as a two-way street. When we talk to people in education and the people in education are trying to teach skills like orthographic processing, having kids be really good at recognizing words very rapidly, and neuroscience has revealed which part of the brain does that in the visual system.
And they’re also teaching children to get better at sounding out words and decoding words, and we know which brain structures do that and we know that they’re all affected in dyslexia. And we are really trying to, I think, use information from the other field to guide us in our hypothesis testing and in our thinking. I think, as I said before, you can use brain imaging as a tool to help contribute to different theoretical frameworks that guide how you think about dyslexia.
And I think we certainly look to education to see how to interpret our work, but I think people in education will look to the brain imaging and understand why it is the work that they do and some of the exercises they do are so important. Because, yes, indeed, if you teach children to recognize word very rapidly, it’s because there are some neurons that are becoming fine-tuned to those words. It’s not just an empty exercise. There’s a physical and physiological mechanism that’s taking place, and that’s shaping the brain to allow that child to become better at that.
How has brain imaging contributed to an awareness of dyslexia?
I think where imaging has made another contribution other than our understanding of the reading brain and the brains of people with dyslexia is that it’s heightened awareness. I think it’s often hard for people to accept there may be a problem. And anybody I think, as a parent, when you have a child who’s a struggling reader, you’re always doubting yourself. Are you just — maybe are you being impatient? Maybe you don’t know enough about it.
And it’s hard to know. And I think sometimes people believe that there’s no such thing as dyslexia. And again, it helps to know that it really is a true phenomenon. And so I think it’s helped raised awareness. I think it’s helped raise understanding. And I certainly hope it’s helped those who have dyslexia understand that their brain is different. It’s certainly something that we emphasize when our children come to our studies.
When they come out of the scanner, we have them take a look at their brain, and it’s not unusual that a child will say, “So where’s my parietal cortex? Where’s my visual word form area?” Because they have already tuned in to the fact that their brain is different, and it’s not their fault, and everybody’s brain is different. And their brain just isn’t all that well-designed to allow them to learn to read as quickly as that of their friends.
How can self-advocacy skills help children with dyslexia?
The schools that I know that show the most enthusiasm for research are the schools that are really specialized for children with learning differences. And what they realize is: first of all is the understanding that it is genetic, that it is biological, that these kids learn differently and that they need very different kind of learning. And also realizing that it’s not just the learning itself but the advocacy piece that these children need.
Often people who realize their kids are struggling with reading not only — primarily they’re looking for tools and interventions to help them become better at reading, but I think you also have to recognize that this is a lifelong condition. And even though these children can make gains in reading, they will continue to struggle and it will hit them again and again as they come into situations that are more difficult, whether they’re going into college or so on.
And so I think it’s really important for these kids to understand what their dyslexia is and what it means for them. And also they have to understand that people don’t understand it. If you ask a person on the street what dyslexia is, very few will tell you, “Oh, it’s a difficulty with learning to read.” They have all sorts of other ideas because of what the media portrays what dyslexia is, which has to do with reversing letters or not being able to walk backwards or something. I don’t know, but there’s all sorts of strange things.
And it’s important for people to know, and it’s important for people with dyslexia to let people know what it is so that they understand what it is they need as learners. It’s important for them to tell their teachers what is helpful to them, to their learning, and that’s something these students really need to learn because when they come to college, they shouldn’t expect the college professor to know what optimizes their learning. And they need to advocate for themselves and make sure that they get that situation settled so that they can benefit from being at college.
What are some misconceptions about dyslexia?
The imaging has helped raise awareness for dyslexia, but it is surprising still how many misconceptions there are about dyslexia. I think it is important that people understand it’s a difficulty with reading words at the text level. It’s that that then impairs their reading comprehension because if they were read the text, they have no difficulties in understanding it and answering questions about it.
And I think it’s important to understand that really the primary treatment that helps is by addressing the difficulties in decoding and understanding how sounds map onto words and to parts of words. And there are misconceptions about other treatment approaches. And there are misconceptions about what dyslexia is. It’s not about reversing letters or seeing things backwards. It’s really about not being able to sound out those words.