Developmental language disorder (DLD) is characterized by receptive or expressive language difficulties or both. Children with the neurodevelopmental condition “struggle to comprehend and use their native language for no obvious reason,” said the authors of a new study. This leads to problems with grammar, vocabulary, and holding conversations, and in turn an increased risk of “difficulties when learning to read, underachieving academically, being unemployed, and facing social and mental health challenges.”
The condition is common and estimated to affect 7% of children – approximately two in every classroom – but is “underrecognized” said the authors.
Saloni Krishnan, PhD, reader at Royal Holloway, University of London, who led the study as a research fellow at the University of Oxford, England, explained: “DLD is a relatively unknown and understudied condition, unlike better known neurodevelopmental conditions such as ADHD, dyslexia, or autism.”
It is suspected that children with DLD may have differences in areas of the brain involved with learning habits and rules. “Although we know that DLD does not result from gross neural lesions, we still do not have a clear picture of how brain anatomy differs in children with DLD,” the authors highlighted.
Language learning difficulties linked to brain differences
For their study,, researchers used an MRI technique called multiparameter mapping (MPM) to investigate microstructural neural differences in children with DLD. The technique measures the properties of brain tissue and is particularly useful for measuring the amounts of myelin.
“Understanding the neural basis of DLD is particularly challenging given the developmental nature of the disorder, as well as the lack of animal models for understanding language,” explained the authors. However, they pointed out that MPM allows an “unparalleled in vivo method” to investigate microstructural neural changes in children with DLD.
Kate Watkins, PhD, professor of cognitive neuroscience at the University of Oxford and senior author, said: “This type of scan tells us more about the makeup or composition of the brain tissue in different areas.”
As part of the Oxford Brain Organisation in Language Development (OxBOLD) study, the researchers recruited and tested 175 children between the ages of 10 and 15 years. Subsequently, 56 children with typical language development and 33 children with DLD were scanned using MPM.
The researchers compared the two groups and found that children with DLD have less myelin in parts of the brain responsible for speaking, listening, and learning rules and habits.
Specifically, maps of magnetization transfer saturation (MTsat) – which index myelin – in children with DLD showed reductions in MTsat values in the caudate nucleus bilaterally, and in the left ventral sensorimotor cortex and Heschl’s gyrus.
“Our findings using this protocol suggest that the caudate nucleus, as well as regions in the wider speech and language network, show alterations in myelin in children with DLD,” explained the authors.
“Given myelin’s role in enabling fast and reliable communication in the brain, reduced myelin content may explain why children with DLD struggle with speech and language processing,” they highlighted.