Language delays in early childhood are common to many people on the autism spectrum, but not to those with Asperger Syndrome. A recent study published in the journal Cerebral Cortex has found that these early language delays leave a signature on the brain, changing its anatomy.
Researchers from the University of Cambridge studies 80 adult men with autism spectrum disorders (ASD), 38 who had delayed language onset and 42 who did not. They found that the men who had delayed language as children had reduced volume of the temporal lobe, insula, and ventral basal ganglia (all key regions in the brain) and larger brainstem structures than the autistic subjects who did not have language delays.
They also found that current language function is linked to a specific pattern of grey and white matter volume changes in some key brain regions, including the frontal, temporal, and cerebellar structures.
Delayed language onset, a child’s first meaningful words coming after 24 months or their first phrase coming after 33 months is considered a subgroup of autism, but is one of the clearest and earliest symptom and cause for assessment of autism or other developmental delays.
Most scientific studies of ASD compare people who are on the spectrum to people who are not, lumping all the subcategories of autism together. Last year, the American Psychiatric Association removed Asperger’s Syndrome as a separate diagnosis from its diagnostic manual, but this study shows a fundamental difference in the architecture of Asperger’s vs. other autism spectrum disorders.
“Although people with autism share many features, they also have a number of key differences,” explained Dr. Meng-Chuan Lai of the Cambridge Autism Research Centre and lead author of the paper. “Language development and ability is one major source of variation within autism. This new study will help us understand the substantial variety within the umbrella category of ‘autism spectrum’. We need to move beyond investigating average differences in individuals with and without autism, and move towards identifying key dimensions of individual differences within the spectrum.”
“This new study shows that a key feature of Asperger Syndrome, the absence of language delay, leaves a long lasting neurobiological signature in the brain. Although we support the view that autism lies on a spectrum, subgroups based on developmental characteristics, such as Asperger Syndrome, warrant further study,” said Professor Simon Baron-Cohen, senior author of the study.
Dr Lai concluded: “It is important to note that we found both differences and shared features in individuals with autism who had or had not experienced language delay. When asking: ‘Is autism a single spectrum or are there discrete subgroups?’ — the answer may be both.”