Earlier this year I posted on a study showing that oxytocin administration improves ability to detect the emotions people display through facial expressions. The authors of the study suggested that oxytocin may play a role in Autism Spectrum Disorders (ASDs) because individuals with ASDs tend to have lower levels of oxytocin on average and more difficulty recognizing emotions. Today at the Society for Neuroscience (SfN) conference, Takahaski Yamada from Showa University in Japan looked more closely at the issue. He showed that for people with ASDs, oxytocin administration improves emotion recognition, but only for emotions that are difficult to identify.
For the experiment, Yamada recruited 19 men with an ASD and 19 men without any ASD as a control group. He tested the ability to recognize emotions after he gave them oxytocin and again after he gave them a placebo. Both the oxytocin and placebo were given through a nasal spray, a technique used in many oxytocin studies. Half the participants received oxytocin first, and the other half received placebo first.
He tested emotion recognition using the Reading the Eyes in the Mind (RMET) task, developed by autism researcher Simon Baron-Cohen. In the RMET, participants see 36 pairs of eyes reflecting an emotion. They simply choose which of four choices of emotion they think the eyes are expressing. Some of the emotions are easy to recognize, such as fear, and some are more challenging, such as bewilderment.
Overall, the control group performed better on the RMET than the group with ASDs. They correctly recognized about 66 percent of the emotions on average, whereas the ASDs only recognized 55 percent. This is not surprising, as the test was designed to show that people with ASDs tend to have more difficulty recognizing emotions.
For both groups, oxytocin did not improve performance overall. Neither group recognized more emotions following oxytocin administration, which is a bit surprising given that a previous study showed that oxytocin improves performance on the test for healthy adults.
Both groups recognized fewer of the difficult emotions. The control group recognized about 45 percent of difficult emotions after placebo and the ASD group recognized around 35 percent.
Here's where it got interesting. Whereas the control group did not improve for difficult emotions following oxytocin dosing, the ASD group showed a marked improvement. The control group got 45 percent correct, but the ASD group now recognized around 43 percent of difficult emotions. They improved about eight points compared to placebo, and almost matched the performance of the control group.
To understand the relationship between severity of ASD and improvement on the task, Yamada calculated how much better each person did at recognizing difficult emotions following oxytocin. He found that the individuals with the most severe ASDs showed the most improvement on the RMET after taking oxytocin.
His findings suggest a possible role for oxytocin in ASDs. Lower levels may be part of the reason why individuals with ASDs tend to have more difficulty recognizing emotions. However, the role of oxytocin may depend on the severity of the disorder.
Although Yamada tested oxytocin's effect in a relatively small group, just 19 autists and 19 controls, he showed some evidence that oxytocin might be a target for better understanding ASDs.