Individuals with Autism spectrum disorders (ASDs) are characterized by social dysfunction, abnormality in speech and communication, and repetitive behaviors. Some researchers suggest the possibility that all or some of these dysfunctions might be attributed to a lack of sufficient orientation to social stimuli, and some previous studies have found that oxytocin may improve social cognition and alleviate these symptoms observed in ASDs.
The present study aims to investigate whether communication difficulty observed in autistic people is related to a lack of sufficient orientation toward social sounds. The present study also explored whether oxytocin could improve the orientation toward social sounds in autistic people.
Sixteen ASD and thirteen typically developed (TD) male adults participated in this study. These two groups were matched in age and IQ. All ASD participants were diagnosed by a team of three experienced psychiatrists and one clinical psychologist. In the experiment, autonomic activities (skin conductance and photoplethysmograph on fingers) toward social and non-social sounds were monitored after ASD and TD participants inhaled oxytocin or placebo (in different sessions). All these sounds were chosen from International Affective Digital Sounds, and their presentation order was pseudo-randomized.
Four-way ANOVAs were used to analyze the effect of oxytocin in individual groups of participants when they heard social, non-social, pleasant, and unpleasant sounds. Compared to TD participants, ASD participants had less sympathetic activities when they inhaled the placebo, but there was no such difference when they inhaled oxytocin. After inhaling oxytocin, all participants tended to have higher sympathetic tones for social sounds than for non-social sounds. The Pearson correlation analysis confirmed that this increase of response toward social sounds compared to non-social sounds was negatively correlated with their social skills in the ASD group.
This is the first study to investigate the effect of oxytocin on sympathetic responses to emotional sounds in autism. Our findings suggest that oxytocin inhalation increases orientation responses toward social sounds in autistic people.