The role of the amygdala in processing social and affective touch

The amygdala plays a central role in socio-emotional behavior, yet its role in processing affective touch is not well established. Longitudinal studies reveal that touch-deprived infants show later in life exaggerated emotional reactivity related to structural and functional changes in the amygdala. The connectivity of the amygdala is well-suited to process the sensory features and the socio-cognitive dimensions of touch. The convergent processing of bottom-up and top-down touch-related inputs in the amygdala triggers autonomic responses. The positive hedonic value of touch in humans and grooming in non-human primates is correlated with vagal tone and the release of oxytocin and endogenous opioids. Grooming reduces vigilance that has been shown to depend critically on the amygdala. Touch-induced vagal tone and lowered vigilance alter neural activity in the amygdala. Under these circumstances neurons no longer respond to each touch stimulus, rather they appear to signal a sustained functional state in which the amygdala appears decoupled from monitoring the external environment.