A child is quiet. He has difficulty reading and writing. He struggles to choose the proper words to express himself. He talks like someone way younger than him. He cannot understand or recall what the people around him were saying. Moreover, he fidgets a lot and always misbehaves during lessons. His teachers are concerned about him and suggest that he should see a clinical psychologist. The clinical psychologist might diagnose him for ADHD, generalized anxiety disorder, or dyslexia. However, in reality, he might have developmental language disorder.
Developmental language disorder, abbreviated as DLD, is a disorder of communication that affects how one understands, learns, and uses language. A UK population study conducted by Norbury et al. in 2016 showed that the prevalence rate of DLD is around 7.58% in primary school children, suggesting that there are two children with DLD in every classroom. Current knowledge suggests that DLD is a lifelong condition with genetic roots. Although it is a relatively common condition, DLD is often overlooked, because individuals with DLD do not show physical signs or severely impaired language abilities. Despite being a hidden condition, individuals with DLD may suffer from long-term consequences in mental health, academic performance, and employment.
To understand the neural basis of DLD to a greater extent, a research team led by Royal Holloway University reader and former Oxford postdoctoral researcher Dr. Saloni Krishnan and Oxford professor of cognitive neuroscience Kate Watkins conducted a quantitative MRI study involving 56 children with typical development and 33 children with DLD. The results of the study showed that children with DLD have reduced striatal myelin in brain areas associated with speaking, listening, and habitual and sequential learning.
Motivation behind the project
Watkins became interested in studying brain differences in individuals with language disorders when she was working with a “very large family that had a gene mutation that caused them to have speech and language problems” as a PhD student. Watkins told Cherwell that her motivation for this study was initiated by Krishnan. She stated: “(Krishnan) came to me a long time ago, saying she really wanted us to look at children with developmental language disorder or DLD using brain imaging. And then we tried many times, because it’s really expensive to do this work, to get funding. We got funding from the (Medical Research Council) for this study.”
Watkins added that she and Krishnan were really lucky to have had “some amazing research assistants” who worked on this project with them.
Having started off as a speech and language therapist, Krishnan told Cherwell that this was a project that was “very, very close to my heart”. “I used to work with children with language disorders,” Krishnan stated. “There’s a little bit more awareness about the importance of spoken language (now), but suddenly, about 10 years ago or so, that wasn’t the case…” After her speech and language therapy degree, Krishnan trained as a cognitive neuroscientist. She said: “I was really, really surprised when we first started this research (about) how little we knew about the brains of children with DLD.”
Krishnan added that while there has been “hundreds if not thousands” of research on autism or ADHD, less than 20 studies have been conducted on the neurophysiological basis of DLD. “Sample sizes (of those studies) tended to be fairly small,” she told Cherwell. “This was a particular issue as well, because … if you have a small number of studies or small sample sizes and the group you’re studying is heterogeneous, it’s not very surprising that everyone has slightly different results.” As part of the BOLD study of brain organization and language development, Krishnan and her colleagues “really wanted to try and identify what might be different (in) the brains of children with DLD”.
Logistical challenges and teamwork
Both Krishnan and Watkins cited obtaining funding as an initial challenge. Krishnan told Cherwell: “No one tells you how difficult funding is… In my case, I did apply for funding four times. And even (for) this particular grant, we submitted it, and it got triaged, which basically meant it didn’t even go to the panel to be discussed. They came back with some things for us to address, and we had to resubmit in order to get funding. Just the process between the triage and when we resubmitted (the application) was nearly a year (long).”
Despite the challenges of obtaining funding, Krishnan’s research team remained supportive. “I really wanted to do it,” Krishnan said. “And as I said, like it was … a struggle to get funding, because I kept getting stuck and rejected. I was really grateful that the final funding came through.” Krishnan also stated that she found out about the eventual funding approval at a neurodevelopmental disorders meeting in Oxford with Watkins and one of the co-writers Dorothy Bishop. “I remember that Dorothy gave both of us a big hug. And Dorothy is not a hugger. It was really exciting. This is the best moment ever.”
Since the research project involved children and young teenagers aged 10 to 15, another challenge Krishnan and Watkins had to consider was keeping the participants still in the MRI machine during the brain imaging process. Krishnan said: “(Children) definitely move more than adults do. But as a team, we have some good strategies to try and keep them as still as we could… One of the best ways to stop children from moving is to show them a movie. We had these very special noise canceling headphones so that they could listen to a movie regardless of their scanner. And… we literally had a movie selection. And they could come and choose before they went into the scanner which movie they were gonna watch.”
Scientific questions about the research project
One interesting question one might ask about DLD is whether it is caused by genes, environmental factors, or a little bit of both. Watkins told Cherwell that the diagnosis of DLD states that the condition should be unexplained. “It can’t be explained by some brain damage, it can’t be explained by some really serious abuse, like being deprived of communication… We know that it isn’t due to parental influence,” Watkins said. “So, in DLD, it’s likely that there is not just one genetic cause, but many – it’s a very heritable disorder. It’s very common for there to be more than one child in the family, for example, or for a parent or a relative to also have some sort of learning difficulty.” Watkins added that although the condition appears to be caused by genes, they would love to learn more about what exact roles specific genes play in the development of the disorder.
Many people might also be interested in why the research team chose to investigate children with DLD rather than adults. In response to this question, Watkins stated: “It’s probably easier to identify the children with DLD. And most of the other research has been on children… Once adults have left the school system, it may be harder to reach them and enroll them in a study… I think just to get the numbers that we needed to get for this study, it was easier to focus on children.”
Krishnan stated that as part of the project, her research team used new quantitative MRI technology to minimize artifacts. “In a traditional scan, it’s the contrast that counts. But in these scans, (it is) actually the numbers – it does give you the same kinds of contrast, but the way you put it together allows you to (quantitatively see the results),” Krishnan said. “(This method) controls for the differences in random field variation. And so it’s really exciting, because it allows you to make more solid inferences about the cellular makeup of the brain.” Krishnan added that contrary to traditional belief, in addition to white matter, gray matter in MRI scans can also represent myelin. “In our paper, we actually focused on gray matter myelin,” she said.
Relevance to the world and the Oxford community
Pembroke College first-year student Deepak Alagusubramanian found the research project “really meaningful”. Alagusubramanian told Cherwell: “I study Philosophy, Politics and Economics. I am excited about the possible implications of such research on public policy, and how the needs of children with development language disorder can be better accommodated, thereby allowing them to integrate better into our society.” He was optimistic that this research would serve as a “stepping stone for further research”, potentially leading to the development of new treatment options and public policies.
Krishnan hopes that schools can create new policies to better accommodate children with DLD. She said that many children with DLD only receive speech and language support services at school from age five to ten. “A lot of times, by the time they are ten and going to secondary school, they get discharged from speech and language services, so the support isn’t the same anymore. But (they) still have the same language problems.” She added that even when they grow into teenagers, these children “always seem to be worse on language than their peers”. “A lot of these things like having poor language will really feed into your exam performance, your social relationships with those around you, and particularly things like getting a job. So I think it’s really interesting to track what would happen after school age, when a lot of this support goes away,” she said.
Krishnan also finds raising awareness of DLD important. She stated: “It may be a better way to think about DLD in the sense that we have this continuum of language abilities. We expect that these children are at the bottom end of the continuum, but they definitely need support.”
However, how exactly should schools support these children? Krishnan believes that there are many interesting school policy debates around the question of inclusion. She stated: “Let’s say, you live in London – you deserve to go to your local school, just like every other child, and you deserve the environment to be tailored to you. Trying to understand how teachers can create that environment, what support we need to provide, and so on, are really interesting and important research questions.”
Watkins also hopes that this research can contribute to creating medical interventions to help children with DLD. She told Cherwell: “Understanding what the kind of underlying neural differences are in the brain (in DLD patients) could … perhaps give us insight into what kind of interventions would work or what kind of interventions wouldn’t work.”
Future DLD research
Krishnan and Watkins hope to conduct further research based on the findings of this project. Watkins stated: “The plan we have next is to try and get some funding to follow up children longitudinally, because this was just a snapshot, a cross sectional study of what they’re like now. What is really important to know is how they change and how they change in relation to how their language changes as well. So, that would be really exciting.”
Both Krishnan and Watkins consider expanding DLD studies to include adult populations important. Watkins told Cherwell that it is difficult to enroll adult participants for DLD research. However, she also said that it is not impossible to involve adults in such studies: “I have colleagues who are doing that, and I definitely would do it.”