Now we know that pupil size and saliva measures might help doctors screen young children for autism spectrum disorders and may point to the brainstem being the seat of the disorder

Now we know that pupil size and saliva measures might help doctors screen young children for autism spectrum disorders and may point to the brainstem being the seat of the disorder 

The brainstem—the part of the brain that controls our most basic involuntary or autonomic responses including salivation and pupil response—is where researchers Christa Anderson and John Colombo are looking for biological characteristics and the neural basis of autism spectrum disorder.

They found two potential biological markers or biomarkers of ASD: larger resting pupil size and altered levels of a salivary enzyme associated with the neurotransmitter norepinephrine in children with the disorder.

The levels of the enzyme, salivary alpha-amylase (sAA) were higher in general across the day and much less variable for children with ASD compared to typically-developing children.

“What this says is that the autonomic system of children with ASD is always on the same level,” said Anderson. “They are in overdrive.”

Collecting sAA levels with a small sponge swab under a child’s tongue and the measurement of pupil size are painless, non-invasive procedures that have the potential for pediatricians to screen children for ASD much earlier and with relatively little expense, said Anderson.

Beyond the exciting possibility of usefulness for early screening, the researchers see pupil size and sAA levels as possible physiological signatures of dysfunction in the autonomic nervous system.

“Many theories of autism propose that the disorder is due to deficits in higher-order brain areas,” said Colombo. “Our findings, however, suggest that the core deficits may lie in areas of the brain typically associated with more fundamental, vital functions.”

Both findings address the Centers for Disease Control’s urgent public health priority goals for ASD: to find biological indicators that can both help screen children earlier and lead to better understanding of how the nervous system develops and functions in the disorder.