Experts say abnormal brain stem activity might explain some of the attention issues seen in autism.

New research has explored how a particular region of the brainstem - the locus coeruleus - 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.

The locus coeruleus is involved in controlling attention in these circumstances.

Because people with autism spectrum disorder show differences in how they regulate their attention, researchers at Carnegie Mellon in the US have explored how the locus coeruleus behaves in individuals with autism.

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.

The team says that this dysregulation might explain exaggerated responses to environmental stimuli, as well as fixated behaviours and interests that characterise autism spectrum disorder.