Infants who are later diagnosed with autism show inconsistent patterns of brain waves in response to the same sound. The unpublished results, presented yesterday at the 2017 International Meeting for Autism Research in San Francisco, California, suggest that this inconsistency could serve as an early biological marker for autism.
“When we think about variability, we usually cringe, because we see variability as a problem or a nuisance, something that gets in the way of what we’re actually trying to measure,” says April Levin, instructor of neurology at Boston Children’s Hospital, who presented the findings. In this case, variability distinguishes children with the condition from those without.
Levin and her colleagues used electroencephalography (EEG) to record brain activity in 3-month-old babies. The study includes 25 ‘baby sibs’ — children who have an older sibling with autism and are thus at increased risk of the condition themselves — as well as 16 babies who have no family history of autism. Of the baby sibs, 11 were diagnosed with autism by age 3.
The researchers recorded brain activity as the infants listened to a recording of a person saying the syllable ‘da’ 100 times. They focused on a brain-wave signal called P150, a spike in neural activity that reflects the brain’s first response to hearing the syllable.
The team analyzed a parameter known as the inter-trial phase coherence, a measure of the timing of the P150 response each time a child hears the syllable. Low coherence indicates variable brain responses, whereas high coherence indicates consistent responses.
Babies later diagnosed with autism have more variable brain responses than do controls or baby sibs without the condition, the researchers found.
The findings jibe with those from previous studies showing that people with autism have inconsistent brain responses to other types of stimuli — such as moving images or puffs of air on the back of the hand. “We’re seeing the same trend at 3 months of age,” Levin says.
It’s unclear how the variability of the brain response relates to the core features of autism. But consistent brain responses are critical for learning. Babies with variable brain responses to the same syllable may never learn to recognize that sound, for example.
“If there’s a lot of variability, that could correlate with the inability to see some degree of consistency in the world,” says Charles Nelson, research director at Boston Children’s Hospital’s Developmental Medicine Center and one of the lead investigators of the project.
That premise is in line with the ‘magical world’ theory, which Pawan Sinha and his colleagues at the Massachusetts Institute of Technology proposed in 2014. According to this theory, children with autism have trouble learning to recognize patterns and make predictions about what might happen next — and, as a result, experience the world as magical and surprising.
Nelson’s team aims to explore whether this variable pattern exists in babies even younger than 3 months. The team is also studying children with mutations that put them at increased risk of autism and related conditions.
Even if this feature is not specific to autism, having markers “for any child who’s on a trajectory of atypical brain development — that’s still very valuable,” says Linda Copeland, a developmental pediatrician at the Center for Autism and Related Disorders in West Sacramento, California, who was not involved in the study. For example, the variability may serve to identify children who would benefit from behavioral therapy.
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