Dyslexia Research Roundup: Some Surprising Findings!

Today we have a dyslexia research roundup for you, and we have three studies that we wanted to share that caught our eye.

Hey everyone, we're Nick and Sonja and this is Dylaxia Journey, and today we're doing something a little different than we've done so far. We're going to take a look at three recent research studies and just delve into them a little bit, what the findings mean. Yeah, so let's jump in. The first study is super recent. The date on it is actually June 2024. I found that it's obviously available online before it's published in the physical paper journal.

So this study is called Motor Skills and Capacities in Developmental Dyslexia, a Systematic Review and Meta-Analysis. And it's in the journal called Acta Psychologica, and we will obviously link to all of these studies in the show notes. So this particular paper is actually called a meta-analysis, where they didn't perform any new research on actual people. They didn't run a research study themselves. It was an analysis of 23 different already published peer-reviewed studies to try and see if there are any trends that emerge when you look at multiple studies of the same topic.

Right, because that kind of information analysis, when they're able to take data from many, many studies like that, often is a powerful way of coming up with statistically significant findings. So that's why they do that. Sort of the power of pulling all the information in together. Exactly. And so, interestingly, and I'm looking at my notes here, when they looked at all 23 of these studies around correlations between dyslexia and motor skills, they found kind of a surprising result, surprising to me at least, which is that they actually showed that there is a correlation between dyslexia and both gross and fine motor skill deficits.

So what that means is that there is an association or someone with dyslexia is, you know, more likely than average to have a, quote, deficit in large motor physical skills, like balance, things like that, and fine motor skills, things that you do with your hands, like bead threading is one example there. And if that makes you start to think dysgraphia for the second part, there's a little more to say about that.

Yeah, even when they discount people specifically with dysgraphia, there's still a correlation there. Right, which is pretty interesting. And then the thing that it made me think about, too, with this particular finding, is that there's quite a few programs out there that work with dyslexic kids in ways where they're working with, I guess I only know some of the specifics. So, you know, sometimes it's catching a ball or it'll work with them often on balance and like these both fine motor and gross motor skills.

And so it's interesting that there is this finding because that's, you know, obviously probably related to why that seems to work for some people. However, it doesn't work for everybody. Right. Because we definitely like we have examples of some people on the dyslexia voices series who that didn't work. Or, and I would say it didn't, we had a little bit of it with our daughter as well. I don't know if it was to enough of an extent that we could say it was tried, though.

So it sort of didn't work, but I would, you know, it maybe wasn't fully tried. But in the other case. It didn't seem effective. Right. But in the other case, I think he did it for much longer than what I'm thinking of. And it didn't work for him. So what does that mean? It doesn't, I personally don't think that that means that to disregard this information at all. What I keep coming back to, you know, and this is just my own thought about it, is that there are really subtypes, subtypes of what then presents as being dyslexic.

Yeah. And a couple other things about that. Even if they discount people with ADHD. Because so one explanation maybe of the fine motor skill deficits is someone with ADHD may not be able to focus on something like that. Even discounting that, there's still the correlation. Right. Right. So that makes it a pretty interesting study in that way. Yeah. Or meta-analysis. Maybe it's better. I almost think it's better to call these meta-analyses because then we remember that it's this kind of information gathering in multiple studies.

And so one obvious question here is like, well, what would the mechanism be? Like what sort of in the brain, you know, is involved in both motor skills and reading? Obviously, we know that there is a correlation, you know, from other studies and just anecdotally, that there is a correlation between dyslexia and handwriting dysgraphia. But anyway, so to get back to the mechanism, though, this again, this meta-analysis, they didn't propose any particular mechanisms, but they did mention some proposals from some of the other studies that they analyzed.

And one proposal there was that it has to do with something, some sort of dysfunction in the cerebellum, which is the, like, part of the brain that's back near the brainstem. And it controls balance and other complex motor functions. And then there's sort of a theory that that could affect things like time estimation that maybe could lead to reading deficits. Which would mean, well, just to say what that would mean, that would be sort of like time deficits, meaning sort of how, it's hard to explain it.

It's like how you are interacting almost with the process of reading and the timing of it. But, yeah, I mean, even just proposing that it's the cerebellum, I think in this case, they're just, you know, they're just saying logically, I think, that that would be the place to look at. It's kind of working backwards, right? That, oh, well, if it's about motor skills and balance and things, then shouldn't we look at the cerebellum?

So it's not like they really were studying the cerebellum. Yeah, I don't think so. I don't particularly buy that proposal. But it makes sense to have that as an area to look at, certainly. Yeah, for sure. Yeah. Yep. So I think that's it about that meta-analysis. So the next two papers that we're going to look at delve into more specifics around brain structure and function. And so it's going to get maybe a little bit more technical, but we'll try to keep it understandable.

So this next one was published in January of 2023. It's called Theories about Developmental Dyslexia by John Stein, and it was published in the journal Brain Sciences. And again, we'll link to that. Can I say really quickly, too, they seem to use the term developmental dyslexia a lot, which I think they just mean dyslexia when they're saying that. They don't seem to, in any of these studies, be talking about subgroups or anything like that.

So I think when they say that, they just mean dyslexia. I think so, too. Yeah. Yeah. And so this paper also didn't run any new experiments. It's himself, the author, it is what is kind of referred to as a synthesis paper where he kind of read a bunch of different studies and tried to synthesize and argue for a particular mechanism of dyslexia based on kind of a lot of different information that's out there.

So in this case, it's not a meta-analysis, though, right? Right. So it's like he's himself synthesizing the information and figuring out what makes sense based on all the studies, as opposed to the other one was trying to look at the statistics when you pull all the information from the studies. And in this case, he's really just presenting his own opinion about a particular mechanism. From having done this deep dive. And so this opinion is actually super interesting, and it's a little bit tricky to explain.

So let me try to start here. So basically, his proposal is that dyslexic people have a, and again, he uses the term deficit, have a deficit in their brain related to timing in the visual processing system. And so the visual processing system is like when you actually take in input through your eyes, and then it gets processed in the brain and interpreted and used. And so when you're reading, sort of the specific timing of when you're looking at each letter and then each phoneme and then each word is obviously very important for proper sequencing and decoding.

So you can see why that already, you know, hypothetically could make sense as an explanation for dyslexia. And so what he points out is that studies have found that in dyslexic people, there is a specific type of brain cell in the visual processing that is involved in the visual processing system. That is, there are much fewer of these particular neurons in dyslexic people. And these are called the magnocellular neurons in the visual processing system.

And this is even observed in infants who later, who later identified as dyslexic, because there's always a question of cause and effect, right? And so similarly, there's another type of neuron involved in the visual processing system that there are more of in dyslexic people. And these are the parvocellular neurons. And these neurons are much smaller. The magnocellular neurons are much bigger. And interestingly, the magnocellular neurons, the ones that there are fewer of in dyslexic people, that, so the magnocellular pathway carries information about large, fast things.

So it's very involved with time, temporal frequencies, the term he uses, and not very involved with spatial awareness. Also, it's colorblind. Whereas the parvocellular pathway, that's what dyslexic people have, a stronger parvocellular pathway, that carries information about small, slow, and colorful things. So very involved with spatial awareness and color, and not involved with time or temporal frequency. So this really kind of correlates with what we generally know about the strengths and weaknesses of dyslexic people.

Just sort of fits, right? Like, without making it more scientific than that, it's like, oh, yeah, that sounds like it makes sense. It fits with what we already know. Right. You want to say a little more about that? Yeah. Which pieces it fits with? Yeah. So, like, you know, the reading deficits can be explained, in his proposal at least, by this time deficiency. And then the spatial awareness and more focus on color actually fits with the, like, enhanced parvocellular pathway.

For example, there are studies that have shown that dyslexic have better, like, red-green distinction, better able to distinguish colors. And we know anecdotally that a lot of dyslexic people are very good at design. They are very particular about colors and things like that. Yeah. So both kind of that design and color part piece and the spatial piece. Yeah. Both seem like they fit. Yeah. And then, additionally, the parvocellular neurons, which there are more of in dyslexic brains, are smaller and normally more extensively connected than the magnocellular neurons.

And so that could also explain why dyslexics are generally better at holistic thinking and making connections across fields and out-of-the-box thinking, creative thinking, that kind of thing. Right. And, again, you know, this may be just one area involved, even though it's what was identified. Right. But it just fits, right? Like, it just seems like, okay, this is at least, like, fits with what we know. Yeah. And so we can't really say, like, cause and effect yet at all.

But it's the association still are really interesting and helpful. Yeah. And this isn't necessarily the answer. Like, dyslexia could be multifactorial, meaning that there are multiple different differences in the brain that are multiple different things, for lack of a better term, that can cause kind of similar problems with reading that we call dyslexia. Right. Right. Right. Or, yeah. Or even in general, even looking at the positive and the what's considered more challenging aspects together.

Like, the whole picture, there could be different systems contributing. But it's still really interesting that they've honed into this particular one. So I did want to mention, you know, there's, I have a little bit of a quibble with saying deficit. I mean, it makes sense if they were, you know, I'm not saying it doesn't make sense. I just said challenge, right? But, like, it makes sense in the sense that they're saying because there are fewer of the magnocellular, that seems to be potentially causing a deficit or challenge in reading.

So you could call it a deficit in that way, you know, as opposed to the average, comparing it to the average. But on the other hand, there was also the discussion at the same time about having more than, for the same reason, right? It's probably just because there's fewer of the one, there's more of the other. It's really probably about the ratio of them. So having, and then saying that there's some of these, like, benefits from it.

So I guess it's like, to me, it's just, to me, it's just better to say difference because why not? Yeah, I mean, you could equally say that people without dyslexia have a surplus of the magnocellular ones and a deficit of the parmacellular, right? Right. Like, you could just turn it around. Like, there's no reason that people without dyslexia, I mean, I guess there is a reason why that's considered the baseline. Because dyslexia is considered the disability.

Yeah. But it's interesting to think about how that framing affects. Right. Right. And you could just as easily just call it a difference. That's all I'm saying. But it's a little, it's just a small quibble there. Yeah. So the motor skill deficits, to use that term again, that we talked about with the first, with the meta-analysis, could, I think, potentially be explained by, by the difference in the visual pathway, at least partially, that this second synthesis paper is arguing for.

Right. So there's some interesting linkages between the meta-analysis and this particular analysis of the studies. And so the third paper that we're going to talk about today is the only one that is actually a new research study with new data. And this one also agrees with the first one. And so this one was published in October of 2022, so it's a couple years old, and it's called Patterns of Neural Functional Connectivity and Infants at Familial Risk of Development of Dyslexia.

And the authors are Chi Yu, Sylvina Faridell, Jade Dunstan et al. There are actually multiple authors listed, and we'll link to that study. It was published in JAMA Network online. So the overall finding here, to kind of summarize, is that infants, so very young children, who have a dyslexic parent or a sibling, that's called a first-degree relative, parent or sibling, with dyslexia, have differences in their brain that are observable with MRI imaging.

So basically, to say that one another way, these very small babies, they're looking at functional MRIs in those babies, and they're able to notice brain differences, and they can, the brain differences, they're able to separate out the groups based on whether or not that infant has a first-degree relative, meaning a parent or sibling in this case, who is dyslexic. Yeah, and we know already from previous studies that dyslexia is inheritable. That's a key kind of assumption of this study, right?

Because they knew that going in, so that was a, yeah, that was probably, like, in their background research for that study. So to get a little more specific into the kind of neuroanatomy here, the differences that they observe involve connectivity or pathways of brain cells, which are called neurons, in one very specific area of the brain. And so interestingly, the study looked at 20 different areas that they chose based on knowing that those 20 different areas are all involved in some way in long-term language and reading development.

And they actually found a statistically significant difference only in one particular area, which is the left fusiform gyrus. And that is involved, interestingly, tying back to the previous paper in visual categorization. So that means that this particular area where we can observe differences in the brain ties back to the high-level vision hypothesis from the previous paper. Yeah. I do want to note that this particular study, like, it was statistically significant, but in my opinion, weak.

There was only around a 55% or a 56% classification accuracy. So what that means is given an fMRI image of an infant's brain, they only had about a 55% or 56% chance of predicting correctly whether that infant has a first-degree relative dyslexia. So that means they were wrong 45% of the time.

One possible, but I mean, but it was a big enough difference that it was statistically significant. So we can't discount it, right? I just think it's a little bit weak. Although one explanation for the weakness is that dyslexia, while inheritable, is only about 50% inheritable, actually. Right. Right. So that could explain why it's such a weak classification accuracy. Or could it be the subgroups again? Right. Because it could be that they're honing in on one particular system, and then it's not going to be true for all the cases.

Right. That's a really good point as well. Yeah.

So, you know, super interesting. Like, I don't know, we can, again, jump to any particular conclusions. But it's nice to see that there are, and this is, like, these three papers that we chose are not the only three papers that have been published about dyslexia over the past couple of years, right? Like, there's a decent amount of research going on in this area. And so it's really nice to see that. I'm kind of encouraged to see that.

You know, hopefully it will lead to kind of some clinical complications. Yeah, right, exactly. Or maybe they'll start to tease out whether or not there's subgroups and some of these other issues. And then hopefully that could lead to eventually maybe identifying people differently, maybe, and then identifying more specifically perhaps what would be the most helpful as a sort of therapy to help with, you know, whether it's the actual, like, working on balance and motor skills, whether it's more visual, whatever that is, hopefully can get more individualized for people.

So, yeah, exactly. Yeah, and one study that I looked at that we don't have time to talk about today, but maybe in a future episode, was actually a study, maybe even a meta-analysis, around, you know, the most effective remediation techniques. So it's good to see that people are studying that as well, as well as the neurological mechanisms here. Yes, definitely. Yeah, and so we're thinking to do some more of this. Let us know in the comments if you'd like to see more about research studies or different kinds of research studies.

Or if you know of a particular research study that you think would be interesting to go through, let us know that as well. Yep. All right. I think that's it for today. Oh, and let us know if you have any questions as well. If any of that wasn't clear, it's definitely a little tricky to try to explain it and take out, you know, some of the very specific terms and jargon while still keeping it as clear as possible.

So let us know if you have any questions about it. We can try to say it another way. Yep. Thanks, everyone, for watching.