Exploring the Brainstem’s Role in Autism Spectrum Disorder

Researchers examine how dysregulation in the brainstem may underpin characteristic behaviors associated with Autism Spectrum Disorder

Today, people are consuming information through a fire hose. Managing this inflow requires people to focus on select pieces of information. People diagnosed with Autism spectrum disorder (ASD) sometimes cannot maintain attention in this way. New research at Carnegie Mellon University explored how a particular region of the brainstem might influence attention in people with autism. The work is published online in the April edition of the Journal Neuroscience.

“Biological differences underlying how individuals with ASD attend to information in their environment can cohesively explain many features of [autism],” said Michael Granovetter, a graduate student in Marlene Behrmann’s lab in CMU’s Department of Psychology and first author on the study. “This study lays the groundwork for future work to see how the locus coeruleus might directly account for characteristics of ASD.”

Previous work using fMRI showed that individuals with autism experience ‘noisy’ neural responses to sensory stimuli compared to controls. The locus coeruleus is a region of the brainstem that regulates noise across the brain. It also helps to focus attention on relevant cues in the environment.

Granovetter and his colleagues explored how this region of the brainstem functions in individuals with autism to see how it may contribute to hypersensitivity to sensory stimuli or fixated behaviors. In the study, he asked 47 adult participants (23 with ASD and 24 age- and gender-matched controls) to participate in an attention-demanding task. During the task, Granovetter and his colleagues monitored pupil dilation, which provides information about locus coeruleus activity.

The participants watched letters flash on a screen and pushed a button if the same letter appeared twice in a row. They repeated this task, while distracted by auditory tones played at random. While all participants performed equally well on the task, the pupils of participants with autism experienced smaller dilations compared to controls under more distracting conditions. Granovetter believes this suggests a dysregulation in activity along the locus coeruleus, which might explain exaggerated responses to environmental stimuli as well as fixated behaviors and interests, which are characteristic of ASD.

The authors note that the physiological effect could not be accounted for by medication and was specific to the responses to the task under distracting conditions. Granovetter cautions while these findings reveal a possible neurobiological mechanism for ASD, the methods used are not diagnostic of ASD.

Granovetter was joined by Charlie Burlingham and David Heeger at New York University, Nancy Minshew at University of Pittsburgh School of Medicine, and Nicholas Blauch and Marlene Behrmann at CMU in the study, titled “Uncharacteristic task-evoked pupillary responses implicate atypical locus coeruleus activity in autism.” The project received funding from the National Institute of General Medical Sciences and the Simons Foundation Autism Research Initiative.