In autism, the brain’s response to speech speaks volumes
When language delays or social detachment mark a baby for a diagnosis of autism, dark clouds cast that child’s future in shadow. But researchers have discovered a test that can reliably forecast, some time between a baby’s first and second birthday, whether those dark clouds will linger or dissipate.
The new study, published Thursday in the journal Neuron, took eight years -- and the participation of 103 babies -- to complete. But if its findings hold up, all it will take in the future to clarify an autistic child’s prognosis is a nap, a mellifluous nursery rhyme and a magnetic resonance imaging scanner.
The new research demonstrates that even in sleep -- and at an age when even some normally developing babies also lack words -- a baby’s brain response to spoken language can reveal whether that child is likely to develop speech, comprehension and social skills or whether his social and expressive disabilities are likely to remain profound.
The new research also sheds new light on autism itself, suggesting it is not just a “spectrum disorder,” but probably more than one disorder -- with more than one cause and very likely more than one approach to effective treatment.
“We discovered the reason why some babies get better and some don’t,” said neuroscientists Eric Courchesne, director of UC San Diego’s Autism Center of Excellence. “That difference is present already at the very beginning, and that suggests there are two very different forms of autism, and that there may be different causes.”
From brain scans of 103 babies, Courchesne’s team found that before her second birthday, a sleeping, normally developing child will typically respond to spoken words with robust activity in the network of brain structures most associated with language, memory, reward, emotion and social judgment. That strong signal shows a stark contrast to activity in the brain regions linked to motor control and sensory processing, which respond to those spoken words with a little to no activity.
In babies who will go on to have the most debilitating form of autism, that relationship is flipped: brain regions linked to motor control and sensory processing will light up strongly in response to spoken language and the constellation of regions typically involved in language, memory and social judgment will go quiet.
Even at this early age, and despite notable language delays, babies who would be diagnosed with autism but go on to develop strong language and social skills had brain-activation patterns that looked like those of the normally developing children.
Courchesne’s ongoing research is focusing on more readily-detectable markers -- both physical and behavioral -- that could also identify autism’s toughest cases and distinguish them from children who, with just a little intervention, will gain near-normal language and social skills.
The findings help explain a long-observed pattern in children with deficits in communication and social skills: despite delays and even persistent behavioral differences, about half go on to develop language and social skills that allow them to navigate society with relative success. The other half fail to develop communication or social skills and often slide backwards from levels reached in early childhood.
“It could be that both are starting in different places,” said Courchesne. “Some may have brain wiring that lends them to being treatment-ready.” Those with the grimmer prognosis, he added, will probably need more intensive intervention to ready them for different treatments.
Sorting children according to those distinctions would be a first step toward better treatment, said Courchesne. At the same time, he added, recognizing the brain-activation pattern that characterizes profound deficits would give clinicians a way to measure a severely autistic child’s response to treatment.
Courchesne’s research also reveals some profound truths about the language capacities of all babies -- and about how early those consequential differences in expressive aptitude are evident. Read a simple sequence of words -- a nursery rhyme -- to a baby asleep in a brain scanner and the pattern of activation you see in the brain speaks volumes about that baby’s future language capacity, Courchesne said.
Even before normally developing babies are stringing together complex phrases, Courchesne said those who will go on to be strongest in language look different in a brain scanner than those whose command of language will be average. In response to spoken words, their brains will show the most extreme contrast between activation in the language, memory and social judgment regions and activation in motor control and sensory processing regions.
That suggests that great communicators are born with those strengths. Although intervention can improve them and neglect might allow them to wither, those strengths are there to be mined from the start, he said.
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