Uncovering The Causes of Stuttering, An Interview With A Neuroscientist

Transcript

Maya Chupkov: 

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Hi I’m Maya Chupkov. And I'm a woman who stutters.

Cynthia Chin: 

And I'm Cynthia chin, Maya's longtime friend, and I know nothing about stuttering.

Maya:

And this is proud stutter, a podcast about stuttering and embracing verbal diversity and an effort to change how we talk about it one conversation at a time. Welcome back to proud stuttered today. We have guessed Frank H. Gunther. Frank is a professor of speech language and hearing sciences at Boston University. Frank, it's so great to have you on the podcast. Great to be here. So I know you have been focusing recently on the underlying causes of stuttering. But before we get into all of that, can you tell us about what led you to become a neuroscientist?

 Frank Guenther:

Sure. So I studied electrical engineering as an undergraduate and master's student and then worked for a couple of years at an engineering firm, decided I was really interested in the brain and kind of wanted to get a job that gave me a little more creativity and a little more. Yeah, just more mystery to solve, as opposed to solving problems that were fairly well solved already. And so going into neuroscience at that time, allowed me to do that, because not that much was known, especially about speech in the brain. But around the time I started graduate school neuroimaging in the form of MRI was developed. And so it was very exciting time where lots was being learned. And there was a lot of room for discovery.

 Cynthia:

Wow, that's amazing. So when did you start kind of using MRIs as a part of your studies?

 Frank:

In the 1990s, around 1998, we ran our first MRI study, I had actually, friends that worked in one of the first imaging centers that did functional brain imaging at Mass General Hospital. And this allowed me to work my way into the system. And I was able to complete a study and use that to get some grant funding to continue work, which I'm still doing to this day, pretty much.

 Cynthia:

Yeah, it's It's wild. how far we've come with technology. I'm surprised that you were working on it way back in the 90s. It feels like new technology to me. Yeah, that Massachusetts General Hospital was actually one of the first centers to do this sort of imaging. Prior to MRI, Positron Emission Tomography or PET had been used to do the very first speech study, which was around 1988.

Maya: 

As far as the history of stuttering research goes, can you hear Give us a summary of like the history of stuttering research and how far it's come. What are like the current research studies being done? And what's what's being explored right now and also, what other mysteries are still out there around stuttering.

 Frank:

So stuttering occurs pretty much in every culture, with the spoken language which all human cultures have. So people have known about it. Pretty much since the beginning of modern humans, and even the ancient Greeks and Romans. Were interested in it had some rough ideas about what might be happening, but really, for centuries, little was known about stuttering, there's no obvious so if you look at the brain of somebody who stuttered after they die, there's nothing obvious in the brain that gives you any clue to why they stuttered. And when I started, actually, in the 1990s, it was only fairly recent that most people in the field thought of it as something of neurogenic. Origin. So a lot of thinking at the time was that it was something stress related or bet, it was a psychological thing that it wasn't, there was no real neural basis for and that is, we know now, not true. But even then, as late as the, you know, late 20th century, people were still, many people were skeptical about whether there was something truly causing stuttering in the brain that it was actually a neurological disorder that had begun to change. And what we believe to be the case now is that it involves a brain region called the basal ganglia. And that had actually been suggested in the early 20s, early 20th century, but not really followed up upon until much later been around 2000 very influential paper was put together by a Swedish scientist named pear arm, who wrote a paper that's published in 2004, which basically reviewed all the available literature on associations between stuttering and various physiological and other behavioral measures, and came down with the view that stuttering had something to do with the basal ganglia being impaired and its ability to generate timing signals for speech for generating for initiating our speech production. We know now for many of the monkey studies that have been done in basal ganglia that there are signals in the basal ganglia that do things like signal the end of a movement. And this sort of signal is important for starting the next movement. And our work has kind of taken that basic idea and tried to flesh it out within the framework of a model that we've developed over the years, that accounts for speech production in the neurologically typical case. And now we're using the model in recent years to investigate disorders of speech. So you may have heard of deep learning, for example, or deep networks. These are a form of neural network.

And so I had been trained and in graduate school as a neural modeler somebody who actually develops equations and runs computer simulations of networks of neurons interacting with each other and producing behaviors. And I started out studying arm movements, there is a lot more available neurophysiological data for arm movements because monkeys move their arms, but they don't speak. And I had developed a model of arm movements in humans and became interested in speech as kind of a parallel to the arm movement system, and became intrigued with it and pretty much switched my focus over to speech production. And stuttering is one that's particularly interesting to me. Because partly because it's so poorly understood it it's it's very common 1% of adults across the world and pretty much every culture stutter, and yet we still have, you know, not the greatest understanding of what's happening. I think I think we've had a lot of impressive And what we know about it in recent years because of neuroimaging and because of modeling work like we've done, and now I think it's a really good time for us to really kind of flesh out what what we think is going wrong. And yeah, and really, finally truly understand what what causes stuttering.

The other issue with stuttering that makes it difficult to study is, as you get older, if you're a person who stutters, you'll often develop secondary behaviors that become associated and they become part of your stuttering movements. But many of those are probably not causing stuttering, they're more of a kind of response to stuttering. And so we are collaborating with colleagues at the University of Michigan, Dr. Susan Chang and her lab, where they are performing neuroimaging studies on children and now are starting to get to the point where they can run functional studies where they actually have the kids producing words in the scanner. And this allows us to measure their brain activity at this crucial stage where they're first starting to develop stuttering behaviors if they're a child who will end up stuttering later as an adult.

Maya: 

Wow, that was a great summary. I honestly, like I don't know if I've ever heard that history kind of verbalized before it in that way. So thank you for that great summary.

 I was curious, because you mentioned that when you become an adult, and you, you know, are still stuttering, and you you, you adapt these different behaviors as a result of stuttering. And then your your, you know, you're unable to, to see, you know, which came first, right, like, is it the stutter? Or is it the behavior? Is there any correlation between, you know, these behavioral developments and whether or not someone has the ability to kind of develop a more fluent speech pattern? And, you know, versus people who are who, you know, continue to stop stutter into their adult life?

 Frank:

Yeah, so one of the things we're doing with collaborative work is kind of following the longitudinal trajectory. Dr. Chang lab is running a longitudinal neuro imaging study that is collecting data at several time points as children progress. And one of the unique things about their work is they, because of this longitudinal design, they're able to look at children who started stuttering by recovered and compare their brains. And we've done studies together where we've identified regions of the brain that seem to correlate with your ability to recover from stuttering in children, so some of the key structures in the brain are so other they're different in a way that's unique to the children who recover compared to both children who don't recover, but also compared to neurotypical children. So there's something unique about their brains.

Maya:

Yeah, we got actually a few questions from our listeners that were interested in this topic. I did notice that studying those with with Parkinson's came up in your research. And I'm curious about that, because my fiance's mom has has has Parkinson's.

 Frank:

Parkinson's disease involves the same brain area that we believe to be the root of the problem and stuttering. And there are other disorders. It's a very complicated brain area and that a wide range of behaviors seem to be affected by function inside this basal ganglia circuit. And Parkinson's disease that when when you look at the literature on you know, co occurrence of Parkinson's for example, in stuttering what you find is that onset of Parkinson's disease in some people can cause stuttering to recur that they had as children but went away. And then they get Parkinson's disease and the stuttering comes back. Conversely, there are people who started stuttering when they got Parkinson's disease. And then if you look at the treatments to Parkinson's disease, they can either alleviate or exacerbate stuttering, depending on the individual.

 Cynthia:

Wow. So it sounds like in your research, you found a lot of you found a lot of correlations between you know, maybe other illnesses and stuttering. Why is it that you think that there still isn't a definitive answer to what causes

 Frank:

Well, part of it is, as I alluded to earlier is because there's no very obvious brain problem. And in recent years, a number of studies have been done, especially on adults, which has its own problems. That alluded to also, where the adults have a mixture of the primary cause of stuttering as well as the secondary consequences. But the studies, each study seems to find some problems some, what we would call anomaly, some different, different pattern than normal in the brains of people who stutter. But the problem is that went from one study to the other, the exact brain areas involved seem to differ. So there's a kind of a lack of consistency across studies. And I think personally, this is because stuttering is really a disorder that occurs at a system level, like a circuit level, and that different parts of the circuit in could be having issues in different people. So one part of the circuit might cause stuttering in one person, whereas a different part might cause stuttering in a different way. And so what this is getting at is that there are probably subtypes of stuttering, that we will eventually need to separate out if we truly want to understand the behavior because otherwise we, we just keep seeing variability from study to study. Overall, we see, for example, most of the studies show some weakening of left hemisphere connectivity, but it's different connections in different people's brains. And from study to study. They don't always find the same regions. And so I think the fact that stuttering is this circuit level problem, it's a fairly subtle problem. It's not a complete shutdown of a system. It's a subtle malfunction that crops up every now and then. But isn't, isn't there all the time.

Maya:

Fascinating. So we have a few listener questions, I told a bunch of our listeners that we were going to be talking with you today, just to preface this, I'm part of a covert stuttering, woman's group and we meet like every other week, and just talk about stuttering and how we're all doing. And one of the things that all of us, actually, that most of us have in common is, we're all either bilingual or multi lingual. And so I'm wondering if there is any neuroscience explanation for whether learning multiple languages in early childhood may predispose someone to stuttering?

 Frank:

That's very interesting as a possibility, I am not aware of studies that have shown that this is a consistent thing. But one possibility. So one of the things that the basal ganglia has to do for fluent speech is it has to recognize exactly when you're just about to finish the last thing that your you did. So if I'm saying a word, and I say the first phoneme and the word, the first sound in the word, I have to, for the basal ganglia to release the second sound, it has to recognize this very precise context involving things like I'm moving at a certain rate, and I have a certain tactile pattern, and I expect this tactile pattern, all of those conditions have to be met. And then the basal ganglia says, Okay, time for the next sound to come out. And I could imagine that if you learn multiple languages, that problem could be exacerbated, like, it's even harder to now recognize the right context, because there's kind of crosstalk between the languages, maybe there are similar sounds or somehow it's, yeah, you know, somehow it's making that job harder to recognize the proper context for generating the next sound. And it's entirely possible that being multilingual exacerbates that slightly.

Maya:

Yeah, I remember, I my first language was Hebrew. And when I started speaking in English, that's when my stuttering happened.

 Frank:

Yeah, and most people who stutter as children do recover, especially women, in fact, roughly an equal number of boys and girls develop stuttering initially, but most women recover and fewer men recover and so by, you know, eight or 10 years of age, there's bias toward having a male female prevalence and stuttering that gets it's pretty high up to three or four to one, but likely I heard that amount will stutter compared to a female will stutter. And it could well be that there are somewhat different mechanisms occurring as I mentioned that basal ganglia is a complicated thing, and there could be different subtypes. Well, there appears to be something about male and female brains that are different that predisposes males to stuttering. And so females may be more resistant to certain certain types of stuttering, but maybe slightly more likely to get to stutter due to a different problem. So one of the things that researchers tend to do is try to look at as uniform a sample as possible. Which means looking at males, because there's so many male, more males that stutter. And I think, relatively little research has been done in females who stutter, for that reason, as children that they're being their brains are being scanned. And one of the things that we hope to see, to learn from our collaboration with the Chang lab, is whether there are different developmental trajectories for males and females that that might give us more insight into what's happening here. And why it's more likely that a male will continue to stutter, compared to a female who's who stuttered as a child as well. Yeah, that's really interesting. I feel like I would go directly to the females and study them first if they if they start off at the same, you know. So I think that it's really interesting.

It's kind of a practical issue, because it's always difficult to get enough subjects for these sorts of studies. And so we, we enroll both males and females, you know, whatever, answers the ad, whoever answers the ads for our studies, we we look at them, but then we'll do a separate analysis for each group. But often there's not enough, there aren't enough females in our groups to do a, you know, to get a good statistical power for comparison. So that's one of the issues that and that's why, you know, that's the main reason why you see far more studies looking at males. In NIH research now, though, they require you to justify why you would use one group versus another, and they require you to do analyses separately.

 Cynthia:

Right. Yeah, that's, that's great that the NIH has guidelines like that, because I know that historically, that's been an issue with women being under studied, right?

Frank:

Exactly. Yeah.

Maya:

Frank, thank you so much. It really as someone who stutters, no, knowing the science, especially what's going on inside the body is just really helpful in me as a stutter, because sometimes I I get so I get so caught up in, in my stutter, and sometimes when I think no, this is just the way my brain is wired. This is something that I can't control. This is something that is physiologically different, or just, and you know, and that really gives me peace of mind in coming to terms with my stuttering and accepting it. So I really appreciate all the work you're doing because personally, as someone who stutters, it means so much that you're so you're so committed to finding the causes of stuttering that maybe can really impact generations of of people who stutter in the future.

 Frank:

That's great to hear. And yeah, thanks for having me. It's been a lot of fun.

Maya:

And that's it for this episode. I'm Maya. And I'm Cynthia, and you've been listening to proud stutter. This episode of proud stutter was produced by me Maya Chupkov.

Cynthia: 

and edited by me, Cynthia chin. Our music was composed by Augusta Denise and our artwork by Mara zekiel, and Noah to call if you have an idea or want to be part of future episodes, find us on Twitter at proud stutter. You can also find us at www dot proud stutter.com drop us a note or share a voice memo. What's your stuttering story? What topics would you like us to cover? And what are you curious about?

Maya: 

And if you liked the show, you can leave us a review wherever you are listening to this podcast.

 Cynthia:

More importantly, tell your friends to listen to

Maya:

Until we meet again. Thanks for listening. Be proud and be you