Difficulty in registering and responding to the facial expressions of other people is a hallmark of autism spectrum disorder (ASD). Relatedly, functional imaging studies have shown that individuals with ASD display altered brain activations when processing facial images.
The hormone oxytocin plays a vital role in the social interactions of both animals and humans. In fact, multiple studies conducted with healthy volunteers have provided evidence for beneficial effects of oxytocin in terms of increased trust, improved emotion recognition, and preference for social stimuli.
This combination of scientific work led German researchers to hypothesize about the influence of oxytocin in ASD. Dr. Gregor Domes, from the University of Freiburg and first author of the new study, explained: "In the present study, we were interested in the question of whether a single dose of oxytocin would change brain responses to social compared to non-social stimuli in individuals with autism spectrum disorder."
They found that oxytocin did show an effect on social processing in the individuals with ASD, "suggesting that oxytocin may help to treat a basic brain function that goes awry in autism spectrum disorders," commented Dr. John Krystal, Editor of Biological Psychiatry.
To conduct this study, they recruited fourteen individuals with ASD and fourteen control volunteers, all of whom completed a face- and house-matching task while undergoing imaging scans. Each participant completed this task and scanning procedure twice, once after receiving a nasal spray containing oxytocin and once after receiving a nasal spray containing placebo. The order of the sprays was randomized, and the tests were administered one week apart.
Using two sets of stimuli in the matching task, one of faces and one of houses, allowed the researchers to not only compare the effects of the oxytocin and placebo administrations, but also allowed them to discriminate findings between specific effects to only social stimuli and non-specific effects to more general brain processing.
What they found was intriguing. The data indicate that oxytocin specifically increases responses of the amygdala to social stimuli in individuals with ASD. The amygdala, the authors explain, "has been associated with processing of emotional stimuli, threat-related stimuli, face processing, and vigilance for salient stimuli."
This finding suggests oxytocin might promote the salience of social stimuli in ASD. Increased salience of social stimuli might support behavioral training of social skills in ASD.
These data support the idea that oxytocin may be a promising approach in the treatment of ASD and could stimulate further research, even clinical trials, on the exploration of oxytocin as an add-on treatment for individuals with autism spectrum disorder.
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