Treatment with the hormone oxytocin boosts brain activity and improves recognition of emotions in people with autism, according to two small studies published in February1, 2.
Oxytocin is a chemical messenger linked to a long list of social behaviors, ranging from empathy to monogamy, in both people and rodents. Preliminary studies suggest that short-term treatment with oxytocin may boost social skills such as emotion recognition in some people with autism. The effects of long-term treatment have not yet been rigorously studied.
Last year, researchers showed that oxytocin may act directly on the brain to hone the response to social information3. In particular, it boosts activity in two brain regions when participants with autism look at pictures of faces, and dampens activity in response to pictures of cars.
The two new studies also show changes in brain activity in response to oxytocin. The first, published in the February issue of Neuropsychopharmacology, looked at emotion recognition in 14 men with autism and 14 controls. The participants looked at 48 pictures, each displaying one of six emotions, as they lay in a functional magnetic resonance imaging scanner. Half of the pictures showed only the eyes, whereas the other half showed only the mouth.
Before taking the test, the men gave themselves three sniffs of a nasal spray containing either oxytocin or placebo. Each participant took the test twice, once after sniffing oxytocin and once after the control spray.
In line with previous studies, the men with autism were less likely to correctly identify emotions from eyes than were controls. Oxytocin improved their ability to do so.
In men with autism but not in controls, oxytocin also boosted brain activity in the amygdala, a brain region that processes emotion. The greater the change in amygdala activity, the greater the improvements in emotion recognition, the study found.
In the other study, published in the February issue of JAMA Psychiatry, researchers looked at the effect of oxytocin on brain activity in 33 men as they watched videos. The videos consist of an actor saying a word that either matches or conflicts with his facial expression and tone of voice. The participants were told to decide whether the actor seemed like a friend or a foe.
Each participant performed the test twice, once after taking oxytocin and once after placebo. Oxytocin boosts brain activity in the prefrontal cortex in people with autism to levels that resemble those in controls, the study found. It also increases the likelihood that men with autism will use nonverbal cues to make judgments, and it shortens their response time in the case of incongruent information.
Together, the two studies suggest that oxytocin may normalize social brain activity in people with autism.