A new study suggests that a small brain region called the habenula may play a role in autism spectrum disorders (ASD).

The habenula is a pea-sized structure located near the thalamus. This structure, Jürgen Germann and colleagues say, “has been identified as the central structure modulating the reward value of social interactions, behavioral adaptation, sensory integration, and circadian rhythm.” All of these, they note, are altered in ASD.

To examine the volume of the habenula in individuals with and without ASD, the researchers analyzed magnetic resonance imaging data on 220 individuals with ASD and 303 age-matched controls. Subjects were between 6 years and 30 years of age.

The researchers found that the habenula was significantly enlarged in individuals with ASD compared to controls, a finding seen across the entire age range. Thus, they say, “the habenula volume difference did not show any evidence of being the product of an altered developmental trajectory.”

In addition, there was no evidence of an association between habenula enlargement and sex or symptom severity on the Social Responsiveness Scale (SRS). “The fact that there is a strong effect of diagnosis independent of age, sex, or symptoms severity as assessed by the SRS score,” they say, “might point to the habenula being implied in a broader range of behavioral symptoms, beyond the classic deficits of social behavior and social interaction.”

The researchers also report that machine modeling based on habenula volume, age, and sex classified ASD with 85% accuracy and 64% accuracy in cross validation. Germann and colleagues caution that their study has a number of limitations. For instance, it did not include very young children, and the number of female subjects was relatively small. However, they say, “the robust finding of increased habenula volume in ASD compared to typically developing control subjects provides the first evidence in human subjects of an involvement of the
habenula in some aspect of the pathophysiology of ASD.”

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“Involvement of the habenula in the pathophysiology of autism spectrum disorder,” Jürgen Germann, Flavia Venetucci Gouveia, Helena Brentani, Saashi A. Bedford, Stephanie Tullo, M. Mallar Chakravarty, and Gabriel A. Devenyi, Nature Scientific Reports, October 27, 2021 (free online). Address: Jürgen Germann, University Health Network, 399 Bathurst Street, Toronto, ON, Canada. Address: Jürgen Germann, germannj@gmail.com

This article originally appeared in Autism Research Review International, Vol. 35, No. 4, 2021