Scimex: A study from the UK, US and Cyprus has found that the very first signs of Autism Spectrum Disorder (ASD) in toddlers appear in brain scans focused on neural activity in language-sensitive regions. The research shows that infants who eventually develop good language abilities light up on the scans, however, the scans show nearly nothing on toddlers who later have a poor language outcome.
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. A study published
by Cell Press April 9th in Neuron 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.
"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," says senior author Eric Courchesne,
co-director of the UC San Diego Autism Center, where the study was
designed and conducted. "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, 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.
"Our
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," says first author Michael Lombardo of the
University of Cyprus.
The researchers also found that, when
combined with behavioral tests, these striking early neural differences
may help predict later language outcome by early childhood. The
prognostic accuracy of the combined neural and behavioral 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," says co-author Karen Pierce, also co-director of the UC San
Diego Autism Center. "These findings open insight into the first steps
that lead to different clinical and treatment outcomes, and in the
future, one can imagine clinical evaluation and treatment planning
incorporating multiple accurate behavioral 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. "Understanding that there are discrete subgroups of early
developing ASD that are distinguished by developmental behavioral
trajectories, neural underpinnings, and brain-behavioral relationships,
really lays the groundwork for a whole range of really fruitful
directions," Lombardo says.