Autism spectrum disorder (ASD) can produce strikingly different clinical outcomes in young children, with some having strong conversation abilities and others not talking at all. Now a study from researchers at University of California, San Diego and University of Cyprus reveals the reason, at the very first signs of possible autism in infants and toddlers, neural activity in language-sensitive brain regions is already similar to normal in those ASD toddlers who eventually go on to develop good language ability but nearly absent in those who later have a poor language outcome. The opensource study is published in Neuron.
The team state that the reason why some toddlers with ASD get better and develop good language and others do not has been a mystery that is of the utmost importance to solve. Discovering the early neural bases for these different developmental trajectories now opens new avenues to finding causes and treatments specific to these two very different subtypes of autism.
The researchers studied 60 ASD and 43 non-ASD infants and toddlers using the natural sleep functional magnetic resonance imaging (fMRI) method developed by the UCSD Autism Center investigators to record brain activity in the participants as they listened to excerpts from children’s stories. All toddlers were clinically followed until early childhood to make a final determination of which ones eventually had good versus poor language outcomes.
In ASD, the team explain, good language outcomes by early childhood were preceded by normal patterns of neural activity in language-sensitive brain regions, including superior temporal cortex, during infant and toddler ages. By contrast, ASD children with poor language outcomes showed very little activity in superior temporal cortex when they were toddlers or infants.
The team state that the current study is important because it’s one of the first large-scale studies to identify very early neural precursors that help to differentiate later emerging and clinically relevant heterogeneity in early language development in ASD toddlers.
The data findings also show that, when combined with behavioural tests, these striking early neural differences may help predict later language outcome by early childhood. The prognostic accuracy of the combined neural and behavioural measures was 80%, compared with 68% for each measure alone.
One of the first things parents of a toddler with ASD want to know is what lies ahead for their child state the researchers, adding that the findings open insight into the first steps that lead to different clinical and treatment outcomes. The team go on to explain that in the future they envision clinical evaluation and treatment planning incorporating multiple accurate behavioural and medical prognostic assessments. That would be a huge practical benefit for families.
Moving forward, the researchers will further investigate the early neural functional substrates that precede and underlie language and social heterogeneity in ASD. They also plan to test the idea that activation, or its absence, in language cortex predicts treatment responsiveness in toddlers with ASD.
Moreover, future research on the molecular underpinnings of variable clinical outcomes in individuals with ASD could pave the way for the development of novel pharmacological interventions. The team surmise that understanding that there are discrete subgroups of early developing ASD that are distinguished by developmental behavioural trajectories, neural underpinnings, and brain-behavioural relationships, really lays the groundwork for a whole range of really fruitful strategies.
Source: UC San Diego Autism Center