The role of the amygdala in processing social and affective touch

Abstract

The amygdala plays a central role in emotion and social behavior, yet its role in processing social and affective touch is not well established. Recent longitudinal studies reveal that touch-deprived infants show later in life exaggerated emotional reactivity that is related to structural and functional changes in multiple brain structures including the amygdala. The internal organization and connectivity of the amygdala is well-suited to process the sensory features of tactile stimuli and also the socio-cognitive dimensions of the received touch. The convergent processing of bottom-up and top-down pathways that carry information about touch results in the elaboration of context appropriate autonomic responses. The positive hedonic value of affective touch in humans and social grooming in non-human primates is correlated with vagal tone and the release of oxytocin and endogenous opioids. Grooming, the non-human primate equivalent of affective touch in humans, also reduces vigilance that has been shown to depend critically on the amygdala. Touch-induced vagal tone and lowered vigilance alter substantially neural activity in the amygdala. Under these circumstances neurons no longer respond phasically to each touch stimulus, rather they appear to signal a sustained functional state in which the amygdala appears decoupled from monitoring the external environment. HighlightsTouch deprivation during early development causes increased emotional reactivity and impaired emotional regulation in later life most likely through amygdala-dependent mechanisms.The amygdala is involved in evaluating the hedonic and social aspects of touch and coordinating autonomic changes that reflect the internal state of the body.Social and affective touch in macaques lowers arousal and vigilance, which is associated with marked changes in amygdala activity.

Human endogenous oxytocin and its neural correlates show adaptive responses to social touch based on recent social context

“…In mice, OT receptor-expressing neurons in the medial amygdala have been found to mediate olfactory-based social familiarity effects ( Ferguson et al, 2001 ). Here, though, stranger touch activated the amygdala in a general fashion ( Figure 4C ; Supplementary file 5 ), supporting the proposal that its prominent role in human and nonhuman primate OT studies may be indirect ( Eckstein et al, 2017 ; Gothard and Fuglevand, 2022 ; Putnam et al, 2018 ).…”

Anxiety and depression: A top‐down, bottom‐up model of circuit function

“…Within the context of BU processing, the amygdala is a critical region in the brain for associative learning, BU processing, and arousal 44,54–56 . The amygdala is also involved in processing changes in the internal state as an important interoception axis 57,58 . What must be noted is the theorized bidirectional relationship between interoception and emotional arousal.…”

“…44,[54][55][56] The amygdala is also involved in processing changes in the internal state as an important interoception axis. 57,58 What must be noted is the theorized bidirectional relationship between interoception and emotional arousal. As internal states change, emotions may arouse through conscious or subconscious evaluation of these homeostatic deviations.…”

Atypical Response to Affective Touch in Children with Autism: Multi-Parametric Exploration of the Autonomic System

“…Nonetheless, pleasant and affective contact can arise from the stimulation of the glabrous part of the hand [ 13 , 14 ], but it is not clear if this perception is mediated by the low density of CT afferents [ 11 ]. Indeed, studies in patients show that the section of the CT tract spares pleasant affective touch perception [ 15 ], suggesting an involvement of A fibers in this percept, possibly via an activation of insula, cingulate regions and amygdala [ 16 , 17 ]. Mechanisms underlying the perception of the pleasantness and affective value of a tactile interaction are thus not yet completely understood (e.g., [ 18 , 19 , 20 ]), especially as, in typical individuals, it is impossible to stimulate CT fibers without also stimulating co-localized A fibers.…”