Support-Giving Is Associated With Lower Systemic Inflammation

BACKGROUND

Support-giving has emerged as a health-relevant social behavior, such that giving more support is associated with better physical health. However, biological mechanisms by which support-giving and health are linked remain unclear. Whether support-giving uniquely relates to health relative to other psychosocial factors is also an open research question.

PURPOSE

Two studies test the hypothesis that support-giving is uniquely (over-and-above other psychosocial factors) related to lower systemic inflammation, a biological correlate of health.

METHODS

Cross-sectional associations of support-giving with markers of systemic inflammation (i.e., interleukin-6 [IL-6], C-reactive protein [CRP]) were examined in two independent samples of midlife adults (Study 1, n = 746; Study 2, n = 350).

RESULTS

Consistent with hypotheses, giving to more social targets (to family and friends, and also volunteering for various causes), but not receiving support from similar targets, was associated with lower IL-6. In conceptual replication and extension with a different measure of support-giving, higher frequency of support-giving behavior was associated with lower IL-6, even after adjusting for social network size and individual differences in social desirability. There were no associations between support-giving and CRP in either sample.

CONCLUSIONS

Future research needs to establish causality and directly test mechanistic pathways, but together, findings reaffirm the health-relevance of support-giving behavior and shed light on a promising biological mechanism by which such effects may occur.

Recalling prior experiences with a close other can fulfill the need for social connection

Humans need social connection to thrive, but how we fulfill this need is not well understood. Numerous theoretical perspectives propose that continual positive experiences with a close other fulfill the need for social connection. Despite popular acceptance for this notion, little research has investigated the consequences of having multiple experiences with a close other. As a first step toward this goal, the current studies assessed whether recalling prior experiences of social connection with a close other alters feelings of satisfaction toward the same person, the implications of such feelings for social desires outside of the lab (Study 1), and possible brain mechanisms related to fulfilling the need for social connection (Study 2). Consistent with hypotheses, recalling experiences increased feelings of satisfaction toward the close other, but not toward an acquaintance. Further, recalling prior experiences uniquely increased the desire for additional social interaction with the close other, compared with others in general. In Study 2, brain regions related to satiety-the ventral striatum (VS) and ventromedial prefrontal cortex (VMPFC)-showed different patterns to recalling prior experiences with a single close other such that VS activity decreased over recalled experiences, while VMPFC activity remained stable. VMPFC activity, but not VS activity, to recalling experiences with a close other was associated with greater feelings of satisfaction. Together, results are consistent with the proposal that positive experiences, particularly with close others, satisfy the need for social connection. Implications for preventing feelings of social disconnection and maintaining social relatonships over time are discussed. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

American prejudice during the COVID-19 pandemic

In the United States, anti-Asian sentiment has pervaded the Coronavirus 2019 (COVID-19) pandemic. Could Americans' fear of contracting the virus relate to prejudice against Asian individuals? According to intergroup threat theory, prejudice increases toward groups of people when they are perceived as a likely cause of symbolic and/or real threat, including disease threat. We tested this perspective in the context of the COVID-19 pandemic by investigating the relationship between Americans' concern about contracting COVID-19 and their feelings toward individuals from multiple countries. Between May 12-14 2020, participants residing in the United States (N = 932) completed an online survey assessing their (1) perceived threat of COVID-19 infection, (2) feelings of warmth and coldness toward people in America, China, Italy, Japan, and Greece, and (3) trait-level prejudice. Perceived threat of COVID-19 infection differentially related to feelings toward American and Chinese nationals and was unrelated to feelings toward people from other countries assessed. Specifically, greater threat of infection was associated with less warmth toward individuals from China, an effect moderated by trait-level prejudice. That is, participants high (but not medium or low) in trait prejudice showed a significant relationship between threat of COVID-19 infection and reduced warmth toward Chinese individuals. Threat of infection also related to greater warmth and less coldness toward American nationals, consistent with prior work indicating that disease threats amplify ethnocentrism. Collectively, results suggest that perceived threat of COVID-19 infection may correspond with prejudice toward the national outgroup associated with the disease's origin (i.e., China), as well as national ingroup favoritism, among Americans prone to prejudice.

Resting (Tonic) Blood Pressure Is Associated With Sensitivity to Imagined and Acute Experiences of Social Pain: Evidence From Three Studies

Social pain is a common experience that has potent implications for health. However, individuals differ in their sensitivity to social pain. Recent evidence suggests that sensitivity to social pain varies according to a biological factor that modulates sensitivity to physical pain: resting (tonic) blood pressure. The current studies extended this evidence by testing whether blood pressure relates to sensitivity to imagined (Study 1: N = 762, 51% female adults) and acute (Study 2, preregistered: N = 204, 57% female adults) experiences of social pain and whether associations extend to general emotional responding (Studies 1-3; Study 3: N = 162, 59% female adults). In line with prior evidence, results showed that higher resting blood pressure was associated with lower sensitivity to social pain. Moreover, associations regarding blood pressure and sensitivity to social pain did not appear to be explained by individual differences in general emotional responding. Findings appear to be compatible with the interpretation that social and physical pain share similar cardiovascular correlates and may be modulated by convergent interoceptive pathways.

Neural correlates of attachment in adolescents with trauma: a preliminary study on frustrative non-reward

Despite the proposed early life origins of attachment style and its implications for risk for psychopathology, little is known about its neurodevelopmental course. Adolescence represents a key transition period when neural substrates of emotion regulation and reward undergo dramatic maturational shifts. Thus, maladaptive coping strategies associated with insecure attachment styles may have an exaggerated effect during adolescence. The current study, therefore, examined the neural correlates of insecure attachment in a diverse sample of adolescents using a frustrative non-reward task (i.e. repeatedly being denied an expected reward). Although there were no significant interactions in the whole-brain activation averaged over the course of the task, the use of complementary analytic approaches (connectivity, change in activation over the course of the task) revealed widespread alterations associated with avoidant attachment during the immediate reaction to, and ensuing recovery from, being denied a reward. Most strikingly, increased avoidant attachment, adjusting for anxious attachment, predicted functional connectivity and change in activity over time in amygdala-prefrontal and frontostriatal networks to reward blocked vs received trials. These patterns were in the opposite direction compared to those exhibited by adolescents lower in avoidant attachment. The findings suggest that negative emotional experiences, such as receiving frustrating feedback, may be uniquely aversive internal experiences for avoidantly attached adolescents and provide preliminary evidence that early coping strategies may persist into adolescence in the form of altered emotion- and reward-related neural patterns.

Prosocial and Positive Health Behaviors During a Period of Chronic Stress Protect Socioemotional Well-Being

Behavior that helps, supports, or protects others—or prosocial behavior—has emerged as a health-relevant behavior that can promote the giver’s well-being, yet whether prosocial behavior protects against the effects of a major, ongoing chronic stressor warrants further examination. Thus, in the context of the 2020 COVID-19 pandemic, we examined whether two types of behaviors—those enacted to prevent the spread of disease to the self and others (positive health behaviors) and those enacted to promote others’ psychological and financial well-being (prosocial behaviors)—might protect well-being over time. Using a longitudinal survey method, 745 participants (M_age = 62.87 years) reported their engagement in positive health behaviors, prosocial behaviors, and socioemotional well-being (depressive symptoms, anxiety symptoms, loneliness) approximately two months into mandated lockdown orders in the USA. Three months later, participants again reported their well-being. Results showed that greater self-reported positive health behaviors (e.g., wearing a facemask, distancing from others) was related to decreased depressive symptoms over time, whereas greater self-reported prosocial behaviors (e.g., donating time or money, thanking an essential worker) was related to decreased loneliness over time. Neither behavior was related to anxiety symptoms. Together, results suggest that both doing things for the benefit of others and engaging in positive health behaviors protects well-being, even during times of chronic stress. Findings are however limited by the use of self-report measures. Future research should use experimental and behavioral approaches beyond self-report to verify findings.

Stress-Related Inflammation and Social Withdrawal in Mothers of a Child With Cancer: A 1-Year Follow-Up Study

OBJECTIVE

Acute inflammation-induced sickness behavior involves changes in social behavior that are believed to promote recovery. Whether chronic inflammation can influence social behaviors in ways that promote recovery is unknown. In a sample of mothers of a child with cancer, this report explores the relationship between inflammation that accompanies the stress of diagnosis and changes in social network, cancer-related stress, and inflammation across 1 year. Three hypotheses tested whether a) initial levels of stress associate with initial levels of inflammation, b) initial levels of inflammation predict social network changes over time, and c) social network changes over time buffer changes in stress and inflammation over time.

METHODS

Cancer-related stress (Impact of Events Scale), social network (social roles and contacts from the Social Network Inventory), and systemic inflammation (circulating interleukin [IL]-6) were assessed in 120 mothers three times after their child's cancer diagnosis: after diagnosis (T1), 6-month follow-up (T2), and 12-month follow-up (T3).

RESULTS

Consistent with predictions, greater cancer-related stress after diagnosis (T1) was associated with higher IL-6 after diagnosis (T1; b = 0.014, standard error [SE] = 0.01, p = .008). In turn, higher IL-6 after diagnosis (T1) was associated with a decrease in social roles over time (T1 ➔ T3; B = -0.030, SE = 0.01, p = .041). Finally, dropping social roles over time (T1 ➔ T3) was associated with decreases in cancer-related stress (B = 25.44, SE = 12.31, p = .039) and slower increases in IL-6 (B = 1.06, SE = 0.52, p = .040) over time.

CONCLUSIONS

This study provides a first indication that chronic stress-related systemic inflammation may predict changes in social behavior that associate with stress recovery and slower increases in inflammation in the year after a major life stressor.

Frontostriatal Functional Connectivity Underlies Self-Enhancement During Social Evaluation

Self-enhancement, the tendency to view oneself positively, is a pervasive social motive widely investigated in the psychological sciences. Relatively little is known about the neurocognitive mechanisms underlying this motive, specifically in social-evaluative situations. To investigate whether positive emotion regulation circuitry, circuitry involved in modulating positive affect, relates to the self-enhancement motive in social contexts, we conducted an functional magnetic resonance imaging (fMRI) study in a healthy young adult sample. We hypothesized that self-enhancement indices (state and trait self-esteem) would relate to greater functional connectivity between right ventrolateral prefrontal cortex (RVLPFC), a region implicated in emotion regulation, and the ventral striatum (VS), a region associated with reward-related affect, during a social feedback task. Following social evaluation, participants experienced stable or decreased state self-esteem. Results showed that stable state self-esteem from pre- to post-scan and higher trait self-esteem related to greater RVLPFC–VS connectivity during positive evaluation. Stable-state self-esteem also related to greater RVLPFC–VS connectivity during negative evaluation. Moreover, RVLPFC activation during all types of feedback processing and left VS activation during negative feedback processing was greater for participants with stable-state self-esteem. These findings implicate neurocognitive mechanisms underlying emotion regulation in the self-enhancement motive and highlight a pathway through which self-enhancement may restore feelings of self-worth during threatening situations.

Relationships Between Early Maternal Warmth and Social Connection: A Randomized Clinical Trial With Naltrexone

OBJECTIVE

Early experiences of having received maternal warmth predict responses to opportunities to connect with others later in life. However, the understanding of neurochemical mechanisms by which such relationships emerge remains incomplete. Endogenous opioids, involved in social connection in both animals and humans, may contribute to this link. Therefore, the current study examined a) relationships between early maternal warmth and brain and self-report responses to novel social targets (i.e., outcomes that may promote social connection) and b) the effect of the opioid antagonist, naltrexone, on such relationships.

METHODS

Eighty-two adult participants completed a retrospective report of early maternal warmth. On a second visit, participants were randomized to 50 mg of oral naltrexone (n = 42) or placebo (n = 40), followed by a magnetic resonance imaging scan where functional brain activity in response to images of novel social targets (strangers) was assessed. Approximately 24 hours later, participants reported on their feelings of social connection since leaving the scanner.

RESULTS

In the placebo condition, greater early maternal warmth was associated with less dorsal anterior cingulate cortex, anterior insula, ventral striatum, and amygdala activity in response to images of novel social targets (r values ≥ -0.360, p values ≤ .031), and greater feelings of social connection (r = 0.524, p < .001) outside of the laboratory. The same relationships, however, were not present in the naltrexone condition.

CONCLUSIONS

Results highlight relationships between early maternal warmth and responses to the social world at large and suggest that opioids might contribute to social connection by supporting the buffering effects of warm early life experiences on social connection later in life.Trial Registration: Clinical Trials NCT02818036.

Beyond social withdrawal: New perspectives on the effects of inflammation on social behavior

Decades of research in animals and humans show that inflammation is an important regulator of social behavior. While much research in this area has concluded that inflammation causes a withdrawal from social interaction, closer examination of the literature reveals that the effects of inflammation on social behavior are much more nuanced. Indeed, while many studies do show that increases in inflammation lead to social withdrawal, other studies show the exact opposite, finding that inflammation leads to an increase in social approach behavior. Critically, whether an organism withdraws or approaches when inflamed may depend on the whether the target of the behavior is a close other or a stranger. In the present paper, we review both animal research and our initial research in humans that has utilized experimental manipulations of inflammation and examined their effects on social approach behavior. We argue, based on complementary theoretical perspectives and supporting evidence from the literature, that there are three critical next steps for translational work examining the effects of inflammation on social behavior: (1) We need to study actual social behavior, as expressed toward both close others and strangers; (2) We should examine not just the social behavior of the inflamed individual, but also the behavior of others interacting with an inflamed individual; and (3) We must consider the relative increases in inflammation (i.e., higher vs. lower) as a contributor to social withdrawal vs. approach. Ultimately, we urge the field to move beyond a singular focus on inflammation and social withdrawal so that we can develop a more comprehensive understanding of the effects of inflammation on a variety of social behaviors.

Replication and extension of the link between the cardiovascular system and sensitivity to social pain in healthy adults

Resting blood pressure (BP) and heart rate variability (HRV) are linked to physical pain. Research also shows a link between social pain and physical pain, and an inverse association between resting BP and social pain. However, little is known regarding the relationship between resting HRV and social pain. Therefore, the present study aimed to replicate the link between social pain and physical pain, and the inverse relationship between resting BP and social pain, and explore the relationship between resting HRV and social pain. One-hundred twenty three healthy adults completed 1) resting cardiovascular measurements of BP and low-frequency (LF) and high-frequency (HF) HRV powers, 2) social pain sensitivity assessment via the Brief Fear of Negative Evaluation (BFNE) and Mehrabian's Sensitivity to Rejection (MSR) scales, and 3) physical pain sensitivity assessment via subjective pain responses during cold pressor test. The results indicated that no association was observed between social pain and physical pain, whereas resting BP was inversely associated with the MSR scores. Resting LF-HRV was inversely associated with social pain, whereas resting HF-HRV was positively associated with social pain. These findings suggest that physical pain and social pain may share biological substrates that are involved in BP regulation and pain control.

Individual differences in resting-state connectivity and giving social support: implications for health

There is a growing appreciation for the health benefits of giving support, though variability in such behavior exists. Based on the possibility that the dorsomedial (DMPFC) default network subsystem is associated with social thinking and behavior, integrity of this subsystem may facilitate giving support to others. The current study tested associations between DMPFC subsystem connectivity at rest and tendencies related to giving support. During a functional magnetic resonance imaging session, 45 participants completed an emotional social cues task, a resting-state scan and self-report measures of social support. Supportive behavior during the month following the scan was also assessed. Greater DMPFC subsystem connectivity at rest was associated with greater support giving (though not receiving or perceiving support) at the time of the scan and one month later. Results held after adjusting for extraversion. In addition, greater resting-state DMPFC subsystem connectivity was associated with attenuated dorsal anterior cingulate cortex, anterior insula and amygdala activity to others’ negative emotional social cues, suggesting that DMPFC subsystem integrity at rest is also associated with the dampened withdrawal response proposed to facilitate care for others in need. Together, results begin to hint at an additional role for the ‘default’ social brain: giving support to others.

The Resting Brain Sets Support-Giving in Motion: Dorsomedial Prefrontal Cortex Activity During Momentary Rest Primes Supportive Responding

Humans give support, care, and assistance to others on a daily basis. However, the brain mechanisms that set such supportive behavior in motion are unknown. Based on previous findings demonstrating that activity in a portion of the brain’s default network—the dorsomedial prefrontal cortex (DMPFC)—during brief rest primes social thinking and behavior, momentary fluctuations in this brain region at rest may prime supportive responding. To test this hypothesis, 26 participants underwent functional magnetic resonance imaging (fMRI) while they alternated between deciding whether to give support to a close other in financial need, receive support for themselves, and make arbitrary decisions unrelated to support. Decisions were interleaved with brief periods of rest. Results showed that, within participants, spontaneous activity in the DMPFC during momentary periods of rest primed supportive-responding: greater activity in this region at the onset of a brief period of rest predicted, on a trial-by-trial basis, faster decisions to give support to the close other. Thus, activating the DMPFC as soon as our minds are free from external demands to attention may help individuals “default” to support-giving. Implications for understanding the prosocial functions of the resting brain are discussed.

Opioids and social bonding: Effect of naltrexone on feelings of social connection and ventral striatum activity to close others

Close social bonds are critical to immediate and long-term well-being. However, the neurochemical mechanisms by which we remain connected to our closest loved ones are not well understood. Opioids have long been theorized to contribute to social bonding via their actions on the brain. But feelings of social connection toward one's own close others and direct comparisons of ventral striatum (VS) activity in response to close others and strangers, a neural correlate of social bonding, have not been explored. Therefore, the current clinical trial examined whether opioids causally affect neural and experiential signatures of social bonding. Eighty participants were administered naltrexone (n = 40), an opioid antagonist that blocks natural opioid processing, or placebo (n = 40) before completing a functional MRI scan where they viewed images of their close others and individuals they had not seen before (i.e., strangers). Feelings of social connection to the close others and physical symptoms commonly experienced when taking naltrexone were also collected. In support of hypotheses, naltrexone (vs. placebo) reduced feelings of social connection toward the close others (e.g., family, friends, romantic partners). Furthermore, naltrexone (vs. placebo) reduced left VS activity in response to images of the same close others, but did not alter left VS activity to strangers. Finally, the positive correlation between feelings of connection and VS activity to close others present in the placebo condition was erased by naltrexone. Effects remained after adjusting for physical symptoms. Together, results lend support to theories suggesting that opioids contribute to social bonding, especially with our closest loved ones. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

A body-to-mind perspective on social connection: Physical warmth potentiates brain activity to close others and subsequent feelings of social connection

Social connection may stem from afferent pathways that bring bodily information to the brain and mind. In support of this perspective, research from animals and humans shows that physical warmth causally affects experiences of social connection. However, whether physical warmth affects feelings of social connection and the brain's response to close others remains unknown. In the current study, 42 participants completed an fMRI scan as they viewed images of a close other and strangers while holding warm, cold, and room-temperature objects. Following the scan, participants reported on their feelings of social connection and pleasure in response to the three temperature conditions. Results revealed a specific effect of physical warmth on brain activity to close others as compared with cooler temperatures (both cold and room temperature) and strangers (e.g., in the ventral striatum, middle-insula, ventromedial prefrontal cortex, pregenual cingulate cortex). Cooler temperatures had no effect on brain activity to close others (vs. strangers). Further, physical warmth increased feelings of social connection, even when adjusting for feelings of pleasure, but not vice versa, suggesting physical warmth may have specific effects on feelings of social connection. Results add to an emerging literature on the contribution of physical warmth to social connection and furthers understanding of why and how connecting with others is a basic need for humans. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Physical and social warmth: Warmer daily body temperature is associated with greater feelings of social connection

Growing evidence suggests that physical warmth and social warmth-feeling socially connected to others-are linked. In particular, thermoregulatory systems that maintain a relatively warm internal body temperature may also support feelings of social connection. However, it is unknown whether and how feelings of physical and social warmth fluctuate together across time in daily life. To this end, the current study examined tympanic temperature, a measure of internal body temperature, and feelings of social connection assessed multiple times a day over 1 week. Consistent with hypotheses, moment-to-moment changes in tympanic temperature covaried with feelings of social connection across assessments. Thus, warmer body temperatures, in the nonfebrile range, were associated with greater feelings of social connection, and cooler body temperatures were associated with lower feelings of social connection. These findings provide further evidence for the link between physical and social warmth and contribute to an understanding of the dynamic fluctuation of affective experience across time. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Naltrexone alters responses to social and physical warmth: implications for social bonding

Socially warm experiences, when one feels connected to others, have been linked with physical warmth. Opioids, hypothesized to support social bonding with close others and, separately, physical warmth, may underlie both experiences. In order to test this hypothesis, 80 participants were randomly assigned to the opioid antagonist, naltrexone or placebo before neural and emotional responses to social and physical warmth were collected. Social and physical warmth led to similar increases in ventral striatum (VS) and middle-insula (MI) activity. Further, feelings of social connection were positively related to neural activity to social warmth. However, naltrexone (vs placebo) disrupted these effects by (i) reducing VS and MI activity to social and physical warmth, (ii) erasing the subjective experience-brain association to social warmth and (iii) disrupting the neural overlap between social and physical warmth. Results provide additional support for the theory that social and physical warmth share neurobiological, opioid receptor-dependent mechanisms and suggest multiple routes by which social connections may be maintained.

Sex Differences in the Relationship Between Inflammation and Reward Sensitivity: A Randomized Controlled Trial of Endotoxin

BACKGROUND

There are robust sex differences in the prevalence of depression. Inflammation and anhedonia may play a role in understanding these sex differences. Indeed, sex differences in inflammation-induced neural responses to reward may provide insight into the sex gaps in depression, but no study has examined this question.

METHODS

As such, the current study examined whether there were sex differences in reward-related neural activity (i.e., ventral striatum [VS] activity) in response to an experimental inflammatory challenge. Human participants (N = 115; 69 female) were randomly assigned to receive either placebo or low-dose endotoxin, which increases inflammation in a safe, time-limited manner. Two hours after receiving placebo or endotoxin (the height of the inflammatory response to endotoxin), participants completed a task in which they anticipated monetary reward in a functional magnetic resonance imaging scanner.

RESULTS

Results demonstrated that endotoxin (vs. placebo) led to reduced VS activity in anticipation of reward and that there were sex differences in this effect. Specifically, in female participants, endotoxin (vs. placebo) led to decreased VS activity in anticipation of reward, but this effect was not present in male participants. In addition, within the endotoxin condition, decreases in VS activity in anticipation of reward were related to increases in inflammation for female but not male participants.

CONCLUSIONS

These findings may have implications for understanding how inflammation may contribute to sex differences in rates of depression.

On the Benefits of Giving Social Support

People who are socially integrated and have strong social ties live happier, longer lives. The link between social connection and well-being is commonly explained in terms of the benefits of receiving care and support from others. However, the benefits of giving care and support to others for the support provider are often overlooked. We review emerging findings that suggest when, why, and how giving support to others provides benefits to the self. We identify possible mechanisms by which these benefits arise and outline boundary conditions that influence such benefits. To gain a richer understanding of the association between social ties and well-being, an important future research direction is to not only consider the support receiver but also emphasize the support provider.

In Sickness and in Health: The Co-Regulation of Inflammation and Social Behavior

Although it has commonly been assumed that the immune system and the processes that govern social behavior are separate, non-communicating entities, research over the past several decades suggests otherwise. Considerable evidence now shows that inflammatory processes and social behavior are actually powerful regulators of one another. This review first summarizes evidence that inflammatory processes regulate social behavior, leading to characteristic changes that may help an individual navigate the social environment during times of sickness. Specifically, this review shows that inflammation: (1) increases threat-related neural sensitivity to negative social experiences (eg, rejection, negative social feedback), presumably to enhance sensitivity to threats to well-being or safety in order to avoid them and (2) enhances reward-related neural sensitivity to positive social experiences (eg, viewing close others and receiving positive social feedback), presumably to increase approach-related motivation towards others who might provide support and care during sickness. Next, this review summarizes evidence showing that social behavior also regulates aspects of inflammatory activity, preparing the body for situations in which wounding and infection may be more likely (social isolation). Here, we review research showing: (1) that exposure to social stressors increases proinflammatory activity, (2) that individuals who are more socially isolated (ie, lonely) show increased proinflammatory activity, and (3) that individuals who are more socially isolated show increased proinflammatory activity in response to an inflammatory challenge or social stressor. The implications of the co-regulation of inflammation and social behavior are discussed.

Exposure to an inflammatory challenge enhances neural sensitivity to negative and positive social feedback

Inflammation, part of the body's innate immune response, can lead to "sickness behaviors," as well as alterations in social and affective experiences. Elevated levels of pro-inflammatory cytokines have been associated with increased neural sensitivity to social rejection and social threat, but also decreased neural sensitivity to rewards. However, recent evidence suggests that inflammation may actually enhance sensitivity to certain social rewards, such as those that signal support and care. Despite a growing interest in how inflammation influences neural reactivity to positive and negative social experiences, no known studies have investigated these processes in the same participants, using a similar task. To examine this issue, 107 participants were randomly assigned to receive either placebo or low-dose endotoxin, which safely triggers an inflammatory response. When levels of pro-inflammatory cytokines were at their peak, participants were scanned using fMRI while they received positive, negative, and neutral feedback from an "evaluator" (actually a confederate) about how they came across in an audio-recorded interview. In response to negative feedback (vs. neutral), participants in the endotoxin condition showed heightened neural activity in a number of threat-related neural regions (i.e., bilateral amygdala, dorsal anterior cingulate cortex) and a key mentalizing-related region (i.e., dorsomedial PFC), compared to placebo participants. Interestingly, when receiving positive feedback (vs. neutral), endotoxin (vs. placebo) led to greater neural activity in the ventral striatum and ventromedial PFC, regions often implicated in processing reward, as well as greater activity in dorsomedial PFC. Together, these results reveal that individuals exposed to an inflammatory challenge are more "neurally sensitive" to both negative and positive social feedback, suggesting that inflammation may lead to a greater vigilance for both social threats and social rewards.

A Pilot Study Examining Physical and Social Warmth: Higher (Non-Febrile) Oral Temperature Is Associated with Greater Feelings of Social Connection

An emerging literature suggests that experiences of physical warmth contribute to social warmth-the experience of feeling connected to others. Thus, thermoregulatory systems, which help maintain our relatively warm internal body temperatures, may also support feelings of social connection. However, the association between internal body temperature and feelings of connection has not been examined. Furthermore, the origins of the link between physical and social warmth, via learning during early experiences with a caregiver or via innate, co-evolved mechanisms, remain unclear. The current study examined the relationship between oral temperature and feelings of social connection as well as whether early caregiver experiences moderated this relationship. Extending the existing literature, higher oral temperature readings were associated with greater feelings of social connection. Moreover, early caregiver experiences did not moderate this association, suggesting that the physical-social warmth overlap may not be altered by early social experience. Results provide additional support for the link between experiences of physical warmth and social warmth and add to existing theories that highlight social connection as a basic need on its own.

Opioids and social bonding: naltrexone reduces feelings of social connection

Close social bonds are critical to a happy and fulfilled life and yet little is known, in humans, about the neurochemical mechanisms that keep individuals feeling close and connected to one another. According to the brain opioid theory of social attachment, opioids may underlie the contented feelings associated with social connection and may be critical to continued bonding. However, the role of opioids in feelings of connection toward close others has only begun to be examined in humans. In a double-blind, placebo-controlled, crossover study of naltrexone (an opioid antagonist), 31 volunteers took naltrexone for 4 days and placebo for 4 days (separated by a 10-day washout period). Participants came to the laboratory once on the last day of taking each drug to complete a task designed to elicit feelings of social connection. Participants also completed daily reports of feelings of social connection while on naltrexone and placebo. In line with hypotheses, and for the first time in humans, results demonstrated that naltrexone (vs placebo) reduced feelings of connection both in the laboratory and in daily reports. These results highlight the importance of opioids for social bonding with close others, lending support to the brain opioid theory of social attachment.

Blocking opioids attenuates physical warmth-induced feelings of social connection

"Heartwarming" social experiences, when one feels interpersonally connected to others, have recently been linked with physical warmth. According to one theory (Panksepp, 1998), "social warmth" and physical warmth may be closely linked because both experiences are supported by similar neurobiological mechanisms; however, the neurochemical substrates underlying this overlap have not been explored. Here, an opioid antagonist, naltrexone, was administered in order to examine the role of opioids, previously shown to alter temperature and social bonding behavior, on perceived thermal intensity, general positive affect, and feelings of social connection from physical warmth. Thirty-one participants took both naltrexone and a placebo and completed a temperature manipulation task (held a warm pack, cold pack, and neutral object) while on each drug. Replicating previous research, holding a warm (vs. a cold or neutral) object increased feelings of social connection. Moreover, blocking opioids reduced this effect. Hence, naltrexone specifically reduced feelings of social connection to holding a warm (vs. neutral) object but not to holding a cold (vs. neutral) object. These results lend further support to the theory that social and physical warmth share neurobiological, opioid receptor dependent mechanisms.

Yearning for connection? Loneliness is associated with increased ventral striatum activity to close others

Loneliness is a distressing state indicating that one's basic need for social connection is not being met. In an effort to satisfy the need for social connection, loneliness may increase the processing of social cues and desire to connect with others. Yet the neural substrates that contribute to the drive for increased connection in response to loneliness are not known. The ventral striatum (VS), previously shown to increase in response to craving food and other rewarding stimuli, may contribute to "social craving" when one is lonely. That is, the VS may track one's 'hunger' for reconnection much as it tracks hunger for food. To examine this, participants reported on their feelings of loneliness before undergoing an fMRI scan where they viewed cues of potential social reconnection (images of a close other). Consistent with the hypothesis that loneliness stems from an unmet need for connection, loneliness was associated with reduced feelings of connection with the close other. Furthermore, greater reported loneliness was associated with increased VS activity to viewing a close other (vs stranger). Results extend the current literature by showing that lonely individuals show increased activity in reward-related regions to their closest loved ones, possibly reflecting an increased desire for social connection.

Shared neural mechanisms underlying social warmth and physical warmth

Many of people's closest bonds grow out of socially warm exchanges and the warm feelings associated with being socially connected. Indeed, the neurobiological mechanisms underlying thermoregulation may be shared by those that regulate social warmth, the experience of feeling connected to other people. To test this possibility, we placed participants in a functional MRI scanner and asked them to (a) read socially warm and neutral messages from friends and family and (b) hold warm and neutral-temperature objects (a warm pack and a ball, respectively). Findings showed an overlap between physical and social warmth: Participants felt warmer after reading the positive (compared with neutral) messages and more connected after holding the warm pack (compared with the ball). In addition, neural activity during social warmth overlapped with neural activity during physical warmth in the ventral striatum and middle insula, but neural activity did not overlap during another pleasant task (soft touch). Together, these results suggest that a common neural mechanism underlies physical and social warmth.

Prediction-error in the context of real social relationships modulates reward system activity

The human reward system is sensitive to both social (e.g., validation) and non-social rewards (e.g., money) and is likely integral for relationship development and reputation building. However, data is sparse on the question of whether implicit social reward processing meaningfully contributes to explicit social representations such as trust and attachment security in pre-existing relationships. This event-related fMRI experiment examined reward system prediction-error activity in response to a potent social reward—social validation—and this activity's relation to both attachment security and trust in the context of real romantic relationships. During the experiment, participants' expectations for their romantic partners' positive regard of them were confirmed (validated) or violated, in either positive or negative directions. Primary analyses were conducted using predefined regions of interest, the locations of which were taken from previously published research. Results indicate that activity for mid-brain and striatal reward system regions of interest was modulated by social reward expectation violation in ways consistent with prior research on reward prediction-error. Additionally, activity in the striatum during viewing of disconfirmatory information was associated with both increases in post-scan reports of attachment anxiety and decreases in post-scan trust, a finding that follows directly from representational models of attachment and trust.

Inflammation selectively enhances amygdala activity to socially threatening images

Although social withdrawal is a prominent symptom of sickness, the mechanisms associated with this behavioral change remain unclear. In animals, the amygdala is a key neural region involved in sickness-induced social withdrawal. Consistent with this, in humans, heightened amygdala activity to negative social cues is associated with social avoidance tendencies. Based on these findings, we investigated whether an experimental inflammatory challenge selectively increased amygdala activity to socially threatening images as well as whether this activity related to feelings of social disconnection. Thirty-nine participants were randomly assigned to receive either placebo or low-dose endotoxin, which increases inflammatory activity. Pro-inflammatory cytokines were assessed at 7 hourly time points via blood draws; self-reported feelings of social disconnection and physical sickness symptoms were assessed hourly as well. Two hours post-injection, participants underwent an fMRI procedure to assess amygdala reactivity during the presentation of socially threatening images (fear faces) as well as non-socially threatening images (guns), socially non-threatening images (happy faces), and non-social, non-threatening images (household objects). Endotoxin led to greater amygdala activity in response to socially threatening vs. all other types of images. No such differences were found for placebo participants. Additionally, increased amygdala activity in endotoxin participants during the viewing of socially vs. non-socially threatening images was associated with increased feelings of social disconnection. These findings highlight the amygdala as a neural region that may be important for sickness-induced social withdrawal. The implications of amygdalar involvement in sickness-induced social withdrawal are discussed.

The Neural Sociometer: Brain Mechanisms Underlying State Self-esteem

On the basis of the importance of social connection for survival, humans may have evolved a “sociometer”—a mechanism that translates perceptions of rejection or acceptance into state self-esteem. Here, we explored the neural underpinnings of the sociometer by examining whether neural regions responsive to rejection or acceptance were associated with state self-esteem. Participants underwent fMRI while viewing feedback words (“interesting,” “boring“) ostensibly chosen by another individual (confederate) to describe the participant's previously recorded interview. Participants rated their state self-esteem in response to each feedback word. Results demonstrated that greater activity in rejection-related neural regions (dorsal ACC, anterior insula) and mentalizing regions was associated with lower-state self-esteem. Additionally, participants whose self-esteem decreased from prescan to postscan versus those whose self-esteem did not showed greater medial prefrontal cortical activity, previously associated with self-referential processing, in response to negative feedback. Together, the results inform our understanding of the origin and nature of our feelings about ourselves.

Subjective responses to emotional stimuli during labeling, reappraisal, and distraction

Although multiple neuroimaging studies suggest that affect labeling (i.e., putting feelings into words) can dampen affect-related responses in the amygdala, the consequences of affect labeling have not been examined in other channels of emotional responding. We conducted four studies examining the effect of affect labeling on self-reported emotional experience. In study one, self-reported distress was lower during affect labeling, compared to passive watching, of negative emotional pictures. Studies two and three added reappraisal and distraction conditions, respectively. Affect labeling showed similar effects on self-reported distress as both of these intentional emotion regulation strategies. In each of the first three studies, however, participant predictions about the effects of affect labeling suggest that unlike reappraisal and distraction, people do not believe affect labeling to be an effective emotion regulation strategy. Even after having the experience of affect labels leading to lower distress, participants still predicted that affect labeling would increase distress in the future. Thus, affect labeling is best described as an incidental emotion regulation process. Finally, study four employed positive emotional pictures and here, affect labeling was associated with diminished self-reported pleasure, relative to passive watching. This suggests that affect labeling tends to dampen affective responses in general, rather than specifically alleviating negative affect.

The neural correlates of persuasion: a common network across cultures and media

Persuasion is at the root of countless social exchanges in which one person or group is motivated to have another share its beliefs, desires, or behavioral intentions. Here, we report the first three functional magnetic resonance imaging studies to investigate the neurocognitive networks associated with feeling persuaded by an argument. In the first two studies, American and Korean participants, respectively, were exposed to a number of text-based persuasive messages. In both Study 1 and Study 2, feeling persuaded was associated with increased activity in posterior superior temporal sulcus bilaterally, temporal pole bilaterally, and dorsomedial prefrontal cortex. The findings suggest a discrete set of underlying mechanisms in the moment that the persuasion process occurs, and are strengthened by the fact that the results replicated across two diverse linguistic and cultural groups. Additionally, a third study using region-of-interest analyses demonstrated that neural activity in this network was also associated with persuasion when a sample of American participants viewed video-based messages. In sum, across three studies, including two different cultural groups and two types of media, persuasion was associated with a consistent network of regions in the brain. Activity in this network has been associated with social cognition and mentalizing and is consistent with models of persuasion that emphasize the importance of social cognitive processing in determining the efficacy of persuasive communication.

Inflammation-induced anhedonia: endotoxin reduces ventral striatum responses to reward

BACKGROUND

Although inflammatory activity is known to play a role in depression, no work has examined whether experimentally induced systemic inflammation alters neural activity that is associated with anhedonia, a key diagnostic symptom of depression. To investigate this, we examined the effect of an experimental inflammatory challenge on the neural correlates of anhedonia-namely, reduced ventral striatum (VS) activity to reward cues. We also examined whether this altered neural activity related to inflammatory-induced increases in depressed mood.

METHODS

Participants (n = 39) were randomly assigned to receive either placebo or low-dose endotoxin, which increases proinflammatory cytokine levels in a safe manner. Cytokine levels were repeatedly assessed through hourly blood draws; self-reported and observer-rated depressed mood were assessed regularly as well. Two hours after drug administration, neural activity was recorded as participants completed a task in which they anticipated monetary rewards.

RESULTS

Results demonstrated that subjects exposed to endotoxin, compared with placebo, showed greater increases in self-reported and observer-rated depressed mood over time, as well as significant reductions in VS activity to monetary reward cues. Moreover, the relationship between exposure to inflammatory challenge and increases in observer-rated depressed mood was mediated by between-group differences in VS activity to anticipated reward.

CONCLUSIONS

The data reported here show, for the first time, that inflammation alters reward-related neural responding in humans and that these reward-related neural responses mediate the effects of inflammation on depressed mood. As such, these findings have implications for understanding risk of depression in persons with underlying inflammation.

Inflammation and social experience: an inflammatory challenge induces feelings of social disconnection in addition to depressed mood

Although research has established links between feelings of social isolation and inflammation, the direction of these effects is unclear. Based on the role that proinflammatory cytokines play in initiating "sickness behavior," which includes symptoms such as social withdrawal, it is possible that inflammatory processes heighten feelings of 'social disconnection.' Here, we examined whether exposure to an inflammatory challenge increased self-reported feelings of social disconnection. In addition, because both inflammatory processes and feelings of social disconnection contribute to depressive symptoms, we also explored whether increases in feelings of social disconnection played a role in the link between inflammation and depressed mood. Participants were randomly assigned to either receive endotoxin, an inflammatory challenge, or placebo. Proinflammatory cytokines (IL-6, TNF-alpha) were collected at baseline and then hourly for 6h. Participants completed self-reports of sickness symptoms ("fatigue"), social disconnection ("I feel disconnected from others"), and depressed mood ("unhappy") hourly. Results revealed that endotoxin led to significant increases (from baseline) in IL-6 and TNF-alpha levels as well as feelings of social disconnection and depressed mood. Moreover, controlling for increases in social disconnection eliminated the relationship between exposure to inflammatory challenge and depressed mood. This study demonstrates that inflammation can have social psychological consequences, which may play a role in cytokine-related depressive symptoms.

An fMRI study of cytokine-induced depressed mood and social pain: the role of sex differences

Although research has demonstrated a relationship between proinflammatory cytokine activity and depressive symptoms, the neurocognitive processes underlying this relationship have remained largely unexplored. Here, we examined the effect of proinflammatory cytokine activation on the neural correlates of socially painful experience and associated depressed mood. Participants received either low-dose endotoxin or placebo through intravenous injection. Levels of the proinflammatory cytokine, IL-6, were repeatedly assessed through hourly blood draws; self-reported depressed mood was assessed hourly as well. Two hours post-injection, participants completed a neuroimaging session in which they were socially excluded during an online ball-tossing game. Replicating previous research, individuals exposed to endotoxin, compared to placebo, showed increases in IL-6 levels and depressed mood. Although there were no meaningful differences between the endotoxin and control groups in neural responses to social exclusion, there were sex differences in the relationships between IL-6 increases and neural responses to exclusion among subjects exposed to endotoxin. Among females, but not males, exposed to endotoxin, increases in IL-6 were associated with increases in social pain-related neural activity (dorsal anterior cingulate cortex, anterior insula) that mediated the relationship between IL-6 increases and depressed mood increases. Implications of these sex differences in the neural correlates of cytokine-associated depressed mood and social pain are discussed.