Abstract:

One of the core symptoms of autism spectrum disorder（ASD）is persistent social dysfunction. The severity of symptoms varies from patient to patient, and there are many different clinical manifestations, such as depression, anxiety, sleep disorders and ADHD. About 30 percent of people with ASD require psychotherapy and psychiatric care, including medication for behavioral problems. In recent years, many studies have indicated that tactile input can affect social function through regulating the oxytocin system. The affective touch conducted by C-fiber promotes the synthesis and release of oxytocin and enhances social motivation and social preference. And the social salience hypothesis of oxytocin hypothesizes that oxytocin regulates the attention orientation of individuals to social information cues in external situations. For example, oxytocin may enhance aggression and competitiveness of individuals in competitive situations while enhance cooperation in social situations. According to the social salience hypothesis of oxytocin, oxytocin increases the salience of social information through enhancing activation of corresponding brain regions. Under this theoretical framework, when social interaction happens, tactile input can enhance the synthesis and release of oxytocin, and oxytocin can also increase the salience of tactile information, which further promotes the occurrence of social interaction. Previous studies have shown that people with ASD have deficits in the oxytocin system. The main manifestations are lower peripheral oxytocin concentration than normal developing individuals and the change of Single Nucleotide Polymorphism（SNP）of oxytocin receptor. People with ASD also show abnormal tactile sensitivity, including hypersensitivity and hyposensitivity. At the peripheral level, they manifest abnormal tactile threshold. At the central level, they manifest abnormal activation in the brain’s affective touch processing regions (such as insula). Compared with typical development, people with ASD show lower activation in social brain network, which maybe is the one reason of abnormal tactile sensitivity. Moderate tactile input can promote the synthesis and release of oxytocin. Thus, we can combine the exogenous oxytocin treatment with auxiliary tactile training together in the future intervening measures. And the interventions for social dysfunction need to start as early as possible. Many people with ASD exhibit abnormal sensory sensitivity in early life, which can affect the quality of parent-child interactions. If infant cannot obtain adequate sensory input from early parent-child interaction, it will cause a growth environment similar to sensory deprivation for infant patients with ASD, which will seriously affect future social functioning in adulthood. Based on the social salience hypothesis of oxytocin, this article summarizes the possible regulations between touch and oxytocin on social function. We point out that the deficits in the oxytocin system can decrease the salience of touch information in people with ASD, reducing the attention resources in social interaction and affecting the emotional feelings for touch. Abnormal tactile sensitivity results in social avoidance, which decreases the synthesis and release of oxytocin in social contact, decreasing the social motivation and social preference, ultimately resulting in social dysfunction. Exploring the interaction between touch, oxytocin system and social function can help us understand the pathogenesis of social dysfunction, and providing new ideas for the prevention and intervention in the future.

Key words: ASD, social touch, oxytocin, social dysfunction, abnormal sensation