Foot massage evokes oxytocin release and activation of orbitofrontal cortex and superior temporal sulcus

Massage may be an important method for increasing endogenous oxytocin concentrations and of potential therapeutic benefit in disorders with social dysfunction such as autism where basal oxytocin levels are typically reduced. Here we investigated oxytocin release and associated neural responses using functional near infrared spectroscopy (fNIRS) during hand- or machine-administered massage. 40 adult male subjects received 10 min of light foot massage either by hand or machine in a counterbalanced order and then rated pleasure, intensity, arousal and how much they would pay for the massage. Blood samples were taken before and after each massage condition to determine plasma oxytocin concentrations. Neural responses from medial and lateral orbitofrontal cortex, superior temporal sulcus and somatosensory cortex were measured (fNIRS oxy-Hb) together with skin conductance responses (SCR), ratings of the massage experience, autistic traits and sensitivity to social touch. Results showed subjects gave higher ratings of pleasure, but not intensity or arousal, after hand- compared with machine-administered massage and there were no differential effects on SCR. Subjects were also willing to pay more for the hand massage. Plasma oxytocin increased after both massage by hand or machine, but more potently after massage by hand. Both basal oxytocin concentrations and increases evoked by hand-, but not machine-administered massage, were negatively associated with trait autism and attitudes towards social touch, but massage by hand-evoked changes were significant in higher as well as lower trait individuals. Increased neural responses to hand vs. machine-administered massage were found in posterior superior temporal sulcus and medial/lateral orbitofrontal cortex but not somatosensory cortex. Orbitofrontal cortex and superior temporal cortex activation during hand massage was associated with the amount of money subjects were willing to pay and between orbitofrontal cortex activation and autism scores. Thus, hand-administered massage can potently increase oxytocin release and activity in brain regions involved in social cognition and reward but not sensory aspects of affective touch. Massage by hand induced changes in both oxytocin concentrations and neural circuits involved in processing social affective trust may have therapeutic potential in the context of autism.