Effects of Appetitive and Aversive Motivational States on Wanting and Liking of Interpersonal Touch

A Comparison of Hugging Frequency and Its Association with Momentary Mood Before and During COVID-19 Using Ecological Momentary Assessment

The COVID-19 pandemic has necessitated a drastic decrease in human social interactions including social touch. One of the most prevalent forms of touch is hugging. Hugging has been demonstrated to benefit both physical and mental well-being. In the present study, we used an ecological momentary assessment approach to assess the relationship between hugging and momentary mood in two independent cohorts sampled prior or during the pandemic. We found that the frequency of hugging was significantly reduced during the pandemic. Using multilevel modeling, we found a significant positive association between momentary mood and daily hugs. This effect was moderated by the cohort, as individuals during the pandemic showed a stronger positive association compared to the cohort sampled prior to the pandemic. While we have to stress that our results are correlational in nature, they potentially indicate that social touch is more beneficial in times of social distancing.

Out of touch? How trauma shapes the experience of social touch - Neural and endocrine pathways

Trauma can shape the way an individual experiences the world and interacts with other people. Touch is a key component of social interactions, but surprisingly little is known about how trauma exposure influences the processing of social touch. In this review, we examine possible neurobiological pathways through which trauma can influence touch processing and lead to touch aversion and avoidance in trauma-exposed individuals. Emerging evidence indicates that trauma may affect sensory touch thresholds by modulating activity in the primary sensory cortex and posterior insula. Disturbances in multisensory integration and oxytocin reactivity combined with diminished reward-related and anxiolytic responses may induce a bias towards negative appraisal of touch contexts. Furthermore, hippocampus deactivation during social touch may reflect a dissociative state. These changes depend not only on the type and severity of the trauma but also on the features of the touch. We hypothesise that disrupted touch processing may impair social interactions and confer elevated risk for future stress-related disorders.

Effects of dopamine and opioid receptor antagonism on the neural processing of social and nonsocial rewards

Rewards are a broad category of stimuli inducing approach behavior to aid survival. Extensive evidence from animal research has shown that wanting (the motivation to pursue a reward) and liking (the pleasure associated with its consumption) are mostly regulated by dopaminergic and opioidergic activity in dedicated brain areas. However, less is known about the neuroanatomy of dopaminergic and opioidergic regulation of reward processing in humans, especially when considering different types of rewards (i.e., social and nonsocial). To fill this gap of knowledge, we combined dopaminergic and opioidergic antagonism (via amisulpride and naltrexone administration) with functional neuroimaging to investigate the neurochemical and neuroanatomical bases of wanting and liking of matched nonsocial (food) and social (interpersonal touch) rewards, using a randomized, between-subject, placebo-controlled, double-blind design. While no drug effect was observed at the behavioral level, brain activity was modulated by the administered compounds. In particular, opioid antagonism, compared to placebo, reduced activity in the medial orbitofrontal cortex during consumption of the most valued social and nonsocial rewards. Dopamine antagonism, however, had no clear effects on brain activity in response to reward anticipation. These findings provide insights into the neurobiology of human reward processing and suggest a similar opioidergic regulation of the neural responses to social and nonsocial reward consumption.

Reliability and validity of a simplified touch experiences and attitudes questionnaire for Chinese college students

Touch cultures have both differences and commonalities in different regions. The Touch Experiences and Attitudes Questionnaire (TEAQ) is a widely applicable self-report tool. The purpose of our research was to examine the validity and reliability of the Chinese version of TEAQ for Chinese college students. We translated the 57 items of the original TEAQ into Chinese and assessed its cultural and linguistic adaptation in Chinese context. Two samples were recruited for the assessment of validity and reliability. The Social Support Rating Scale, Index of Well-being Scale and Security Questionnaire were chosen as criterion-related validity indicators. Item analysis, principal component analysis and confirmatory factor analysis indicated that the simplified Chinese version of TEAQ contained 18 items in three factors: Attitude to Intimate Touch, Childhood Touch and Current Positive Touch, with a cumulative variance contribution rate of 57.12%. The 3-factor model had good validity and reliability. The TEAQ was positively correlated with social support, sense of security and well-being. There were demographic differences in sex and left-behind experience. We anticipate the simplified TEAQ will be a valuable tool for the research of touch among Chinese college students.

Role of medial prefrontal cortex and primary somatosensory cortex in self and other-directed vicarious social touch: a TMS study

Conflicting evidence points to the contribution of several key nodes of the 'social brain' to the processing of both discriminatory and affective qualities of interpersonal touch. Whether the primary somatosensory cortex (S1) and the medial prefrontal cortex (mPFC), two brain areas vital for tactile mirroring and affective mentalizing, play a functional role in shared representations of C-tactile (CT) targeted affective touch is still a matter of debate. Here, we used offline continuous theta-burst transcranial magnetic stimulation (cTBS) to mPFC, S1 and vertex (control) prior to participants providing ratings of vicarious touch pleasantness for self and others delivered across several body sites at CT-targeted velocities. We found that S1-cTBS led to a significant increase in touch ratings to the self, with this effect being positively associated to levels of interoceptive awareness. Conversely, mPFC-cTBS reduced pleasantness ratings for touch to another person. These effects were not specific for CT-optimal (slow) stroking velocities, but rather they applied to all types of social touch. Overall, our findings challenge the causal role of the S1 and mPFC in vicarious affective touch and suggest that self- vs other-directed vicarious touch responses might crucially depend on the specific involvement of key social networks in gentle tactile interactions.

Opioid-blunted cortisol response to stress is associated with increased negative mood and wanting of social reward

Animal research suggests a central role of the μ-opioid receptor (MOR) system in regulating affiliative behaviors and in mediating the stress-buffering function of social contact. However, the neurochemistry of stress-related social contact seeking in humans is still poorly understood. In a randomized, double-blind, between-subjects design, healthy female volunteers (N = 80) received either 10 mg of the µ-opioid agonist morphine sulfate, or a placebo. Following a standardized psychosocial stress induction, participants engaged in a social reward task, in which the motivation to obtain skin-to-skin social touch and the hedonic reactions elicited by such touch were assessed. Morphine prevented the increase of salivary cortisol typically observed following acute stress exposure. Notably, this altered HPA axis responsivity was associated with increased negative affect in response to psychosocial stress, and with enhanced subjective wanting of highly rewarding social contact. These findings provide novel evidence on the effect of exogenous opioids administration on the reactions to psychosocial stress and point to a state-dependent regulation of social motivation.

Positive Affect: Nature and brain bases of liking and wanting

The positive affect of rewards is an important contributor to well-being. Reward involves components of pleasure 'liking', motivation 'wanting', and learning. 'Liking' refers to the hedonic impact of positive events, with underlying mechanisms that include hedonic hotspots in limbic brain structures that amplify 'liking' reactions. 'Wanting' refers to incentive salience, a motivational process that makes reward cues attractive and able to trigger craving for their reward, mediated by larger dopamine-related mesocorticolimbic networks. Under normal conditions, 'liking' and 'wanting' cohere. However, 'liking' and 'wanting' can be dissociated by alterations in neural signaling, either induced in animal neuroscience laboratories or arising spontaneously in addictions and other affective disorders, which can be detrimental to positive well-being.