Changes in brain attention may underlie autism

The findings suggest those with ASD may have dysregulation in locus coeruleus activity.

Summary: Those on the autism spectrum had atypically smaller pupil dilation compared to the control group during distracting conditions while taking a push-button test. The findings suggest those with ASD may have dysregulation in locus coeruleus activity. The dysregulation of the LC may explain the exaggerated responses to environmental stimuli and fixated behaviors many with ASD experience.

Source: SfN

New research in Journal of Neuroscience explores how a particular region of the brainstem might explain differences in attention in people with autism.

In day-to-day life, we are confronted with an abundance of information, and have to be able to selectively attend to the most relevant aspects of our environment. A region of the brainstem called the locus coeruleus is involved in controlling attention. Because people with autism spectrum disorder show differences in how they regulate their attention, Granovetter et al. explored how the locus coeruleus behaves in individuals with autism.

This shows a chart from the study
People with autism have less pupil dilation compared to controls while they are distracted, revealing dysregulated activity in the locus coeruleus. The image is credited to Granovetter et al., JNeurosci 2020.

Researchers had participants perform an attention-demanding task and monitored their pupil dilation, which provides information about locus coeruleus activity.

Adult participants watched letters flash on a screen and pushed a button if the same letter appeared twice in a row. They then repeated this task with a distraction — auditory tones played at random times. All participants performed equally well on the task, but participants with autism had atypically smaller pupil dilations compared to controls during the more distracting condition, suggesting a dysregulation in locus coeruleus activity.

This dysregulation might explain exaggerated responses to environmental stimuli as well as fixated behaviors and interests that characterize autism spectrum disorder.

About this ASD research article

Source:
SfN
Media Contacts:
Calli McMurray – SfN
Image Source:
The image is credited to Granovetter et al., JNeurosci 2020.

Original Research: Open access
“Uncharacteristic Task-Evoked Pupillary Responses Implicate Atypical Locus Coeruleus Activity in Autism”. Michael C. Granovetter, Charlie S. Burlingham, Nicholas M. Blauch, Nancy J. Minshew, David J. Heeger and Marlene Behrmann.
Journal of Neuroscience doi:10.1523/JNEUROSCI.2680-19.2020.

Abstract

Uncharacteristic Task-Evoked Pupillary Responses Implicate Atypical Locus Coeruleus Activity in Autism

Autism spectrum disorder (ASD) is characterized partly by atypical attentional engagement, reflected in exaggerated and variable responses to sensory stimuli. Attentional engagement is known to be regulated by the locus coeruleus (LC). Moderate baseline LC activity globally dampens neural responsivity and is associated with adaptive deployment and narrowing of attention to task-relevant stimuli. In contrast, increased baseline LC activity enhances neural responsivity across cortex and widening of attention to environmental stimuli regardless of their task relevance. Given attentional atypicalities in ASD, this study is the first to evaluate whether, under different attentional task demands, individuals with ASD exhibit a different profile of LC activity compared to typically developing controls. Males and females with ASD and age- and gender-matched controls participated in a one-back letter detection test while task-evoked pupillary responses—an established correlate for LC activity—were recorded. Participants completed this task in two conditions, either in the absence or presence of distractor auditory tones. Compared to controls, individuals with ASD evinced atypical pupillary responses in the presence versus absence of distractors. Notably, this atypical pupillary profile was evident despite the fact that both groups exhibited equivalent task performance. Moreover, between-group differences in pupillary responses were observed specifically in response to task-relevant events, providing confirmation that the group differences most likely were specifically associated with distinctions in LC activity. These findings suggest that individuals with ASD show atypical modulation of LC activity with changes in attentional demands, offering a possible mechanistic and neurobiological account for attentional atypicalities in ASD.

Significance Statement

Individuals with autism spectrum disorder (ASD) exhibit atypical attentional behaviors, including altered sensory responses and atypical fixedness, but the neural mechanism underlying these behaviors remains elusive. One candidate mechanism is atypical locus coeruleus (LC) activity, as the LC plays a critical role in attentional modulation. Specifically, LC activity is involved in regulating the tradeoff between environmental exploration and focused attention. This study shows that, under tightly controlled conditions, task-evoked pupil responses—an LC activity proxy—are lower in individuals with ASD than in controls, but only in the presence of task-irrelevant stimuli. This suggests that individuals with ASD evince atypical modulation of LC activity in accordance with changes in attentional demands, offering a mechanistic account for attentional atypicalities in ASD.

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