A new study suggests that a common characteristic of autism – language delay in early childhood – results in lasting differences in the brain. Understanding such differences may lead to the identification of autism subtypes and the development of more-personalized supports and treatments, the authors propose.
Their report appears in the journal Cerebral Cortex. It was funded, in part, by European Autism Interventions – a Multicentre Study for Developing New Medications (EU-AIMS). Autism Speaks is an active partner of EU-AIMS.
“The identification of underlying differences in anatomy and physiology – in the brain and throughout the body – are important for understanding autism and advancing personalized, more effective interventions and treatments,” comments Daniel Smith, Autism Speaks senior director of discovery neuroscience. “If these findings pan out, it might make sense for researchers and therapists to double-down on speech and language interventions and medicines that specifically engage the altered brain regions.” (Dr. Smith was not directly involved in the research.)
"Although people with autism share many features, they also have a number of key differences," says the study’s lead author, Meng-Chuan Lai of England’s Cambridge Autism Research Centre. "This new study will help us understand the substantial variety within the umbrella category of autism spectrum.”
The researchers studied 80 men with autism using MRI brain imaging. Roughly half (38) had language delay as children. By definition, language delay involves no meaningful words before 24 months of age or no phrases of speech by 33 months. Such delays occur in many but not all children with autism and are among the issues most likely to trigger an autism assessment.
Findings from MRI brain scans
In their study, the researchers associated language delay with significant size differences in a number of key brain areas:
The insula and temporal lobe of the cerebral cortex and the brain’s ventral basal ganglia were all smaller in the participants who had early language delay. Generally speaking, these areas control higher thought, movement, perceptions and behavioral responses. By contrast, the brainstem was larger in this delayed-language group. The brain stem serves as both a relay station for messages between brain areas and controls involuntary movements such as breathing and heartbeat. (See brain chart below.)
"This suggests there are potentially long-lasting effects of delayed language onset on the brain in autism," Dr. Lai says. However, the researchers could not determine whether early language delays produced the differences in brain anatomy or vice versa.
Additionally, the researchers associated differences in the men’s current language abilities with size differences in other key brain regions, particularly the temporal and frontal lobes of the cerebral cortex and in the cerebellum.
In flagging the differences in brain anatomy, the researchers raised concern about the American Psychiatric Association folding all subtypes of autism into one umbrella diagnosis of autism spectrum disorder in the new DSM-5 diagnostic manual, last year. This eliminated the separate diagnosis of Asperger syndrome, which by definition applied to those on the autism spectrum who did not have language delays or limitations.
(Also see: “DSM-5: Your Questions Answered.”)
“Although we support the view that autism lies on a spectrum, subgroups based on developmental characteristics such as Asperger syndrome warrant further study,” says study co-author Simon Baron-Cohen, also of Cambridge University.
Study also finds commonalities
At the same time, the researchers found more commonalities than differences among the brains of all the men with autism – as compared to the brains of men without the disorder.
Concludes Dr. Lai, "When asking: 'Is autism a single spectrum or are there discrete subgroups?' – the answer may be both."