Acute social isolation evokes midbrain craving responses similar to hunger

Let me in: The neural correlates of inclusion motivation in loneliness

BACKGROUND

While it is well-established that humans possess an innate need for social belonging, the neural mechanisms underlying motivation for connection are still largely unknown. We propose that inclusion motivation - measured through the effort that individuals are willing to invest to be included in social interactions - may serve as one of the basic building blocks of social behavior and may change in lonely individuals.

METHODS

Following the screening of 303 participants, we scanned 30 low- and 28 high-loneliness individuals with functional magnetic resonance imaging while they performed the Active Inclusion Task (AIT). The AIT assesses the participants' levels of effort invested in influencing their inclusion during classic Cyberball conditions of fair play and exclusion.

RESULTS

High- compared to low-loneliness individuals showed higher urgency for inclusion, specifically during fair play, which correlated with higher activity in the right thalamus. Furthermore, in high-loneliness individuals, we found increased functional connectivity between the thalamus and the temporoparietal junction, putamen, and insula.

LIMITATIONS

Participants interacted with computerized avatars, reducing ecological validity. Additionally, although increasing inclusion in the task required action, the physical demand was not high. Additional limitations are discussed.

CONCLUSIONS

Inclusion motivation in loneliness is heightened during fair but not exclusionary interactions, and is linked to activity in brain regions implicated in appetitive behavior and social cognition. The findings indicate that lonely individuals may view threat in inclusionary interactions, prompting them to take action to regain connection. This suggests that inclusion motivation may help explain social difficulties in loneliness.

Negative impacts of social isolation on behavior and neuronal functions are recovered after short-term social reintroduction in zebrafish

Recently, social isolation measures were crucial to prevent the spread of the coronavirus pandemic. However, the lack of social interactions affected the population mental health and may have long-term consequences on behavior and brain functions. Here, we evaluated the behavioral, physiological, and molecular effects of a social isolation (SI) in adult zebrafish, and whether the animals recover such changes after their reintroduction to the social environment. Fish were submitted to 12 days of SI, and then reintroduced to social context (SR). Behavioral analyses to evaluate locomotion, anxiety-like and social-related behaviors were performed after SI protocol, and 3 and 6 days after SR. Cortisol and transcript levels from genes involved in neuronal homeostasis (c-fos, egr, bdnf), and serotonergic (5-HT) and dopaminergic (DA) neurotransmission (thp, th) were also measured. SI altered social behaviors in zebrafish such as aggression, social preference, and shoaling. Fish submitted to SI also presented changes in the transcript levels of genes related to neural activity, and 5-HT/DA signaling. Interestingly, most of the behavioral and molecular changes induced by SI were not found again 6 days after SR. Thus, we highlight that SR of zebrafish to their conspecifics played a positive role in social behaviors and in the expression of genes involved in different neuronal signaling pathways that were altered after 12 days of SI. This study brings unprecedented data on the effects of SR in the recovery from SI neurobehavioral alterations, and reinforces the role of zebrafish as a translational model for understanding the neurobiological mechanisms adjacent to SI and resocialization.

A translational neuroscience perspective on loneliness: Narrative review focusing on social interaction, illness and oxytocin

This review addresses key findings on loneliness from the social, neurobiological and clinical fields. From a translational perspective, results from studies in humans and animals are included, with a focus on social interaction, mental and physical illness and the role of oxytocin in loneliness. In terms of social interactions, lonely individuals tend to exhibit a range of abnormal behaviors based on dysfunctional social cognitions that make it difficult for them to form meaningful relationships. Neurobiologically, a link has been established between loneliness and the hypothalamic peptide hormone oxytocin. Since social interactions and especially social touch regulate oxytocin signaling, lonely individuals may have an oxytocin imbalance, which in turn affects their health and well-being. Clinically, loneliness is a predictor of physical and mental illness and leads to increased morbidity and mortality. There is evidence that psychopathology is both a cause and a consequence of loneliness. The final section of this review summarizes the findings from social, neurobiological and clinical perspectives to present a new model of the complex construct of loneliness.

Sex differences in the social motivation of rats: Insights from social operant conditioning, behavioural economics, and video tracking

BACKGROUND

Social behaviour plays a key role in mental health and wellbeing, and developing greater understanding of mechanisms underlying social interaction-particularly social motivation-holds substantial transdiagnostic impact. Common rodent behavioural assays used to assess social behaviour are limited in their assessment of social motivation, whereas the social operant conditioning model can provide unique and valuable insights into social motivation. Further characterisation of common experimental parameters that may influence social motivation within the social operant model, as well as complementary methodological and analytical approaches, are warranted.

METHODS

This study investigated the effects of biological sex, housing condition, and time-of-day, on social motivation using the social operant model. This involved training rats to lever press (FR1) for 60-s access to a social reward (same-sex conspecific stimulus). Subjects were male and female Wistar rats, housed under individual or paired conditions, and sessions were conducted either in the mid-late light phase (ZT6-10) or early-mid dark phase (ZT13-17). A behavioural economics approach was implemented to measure social demand and the influence of stimulus partner sex (same- vs. opposite-sex stimulus) on social operant responding. Additionally, video tracking analyses were conducted to assess the degree of convergence between social appetitive and consummatory behaviours.

RESULTS

Biological sex, housing conditions, the interaction between sex and housing, and stimulus partner sex potently influenced social motivation, whereas time-of-day did not. Behavioural economics demonstrated that sex, housing, and their interaction influence both the hedonic set-point and elasticity of social demand. Video analysis of social interaction during social operant sessions revealed that social appetitive and consummatory behaviours are not necessarily convergent, and indicate potential social satiety. Lastly, oestrus phase of female experimental and stimulus rats did not impact social motivation within the model.

CONCLUSIONS

Social isolation-dependent sex differences exist in social motivation for rats, as assessed by social operant conditioning. The social operant model represents an optimal preclinical assay that comprehensively evaluates social motivation and offers a platform for future investigations of neurobiological mechanisms underlying sex differences in social motivation. These findings highlight the importance of continued consideration and inclusion of sex as a biological variable in future social operant conditioning studies. Humans are social creatures-our everyday interactions with others and the support this provides play a key role in our wellbeing. For those experiencing mental health conditions, people's motivation to engage with others can wane, which can lead them to withdraw from those who support them. Therefore, to develop better treatment strategies for these conditions, we need to gain a deeper understanding of social motivation. Studying social behaviour in animals can facilitate this investigation of social motivation as it allows for a causal understanding of underlying neurobiology that is not possible in human experiments. An optimal way to study social motivation in animals is using the social operant conditioning model, where rats learn to press a lever that opens a door and allows them to interact with another rat for a short time. This study characterised the social operant model by testing whether sex, housing conditions, time-of-day, and the sex of the stimulus partner influence rats' motivation to seek interaction with another rat. We found that female rats were more socially motivated than males, and that rats living alone were more motivated than those living with another rat; interestingly, this effect of housing affected females more than males. Regardless of sex, rats were more motivated to interact with a rat of the opposite sex. These findings provide insights into sex differences in social motivation in rats and new insights into the social operant model which will help guide future research into social motivation and other mental health conditions.

Effects of Highly Palatable Diet on motivation for food and resistance to punishment in rats: Role of sex and age of exposure

Exposure to highly palatable food is believed to induce behavioral and neurobiological changes that may produce addiction-like behavior and increase the risks of obesity and overweight. Studies in rodents have led to conflicting results suggesting that several factors such as sex and age of exposure contribute to the development of maladaptive behaviors towards food. In addition, it is not clear whether effects of exposure to highly palatable diets (HPD) persist after their discontinuation, which would indicate long-term risks to develop addiction-like behavior. In this study, we investigated the persistent effects of an intermittent 8-week exposure to HPD in male and female rats as a function of age of exposure (adult and adolescent). We found that intermittent exposure to HPD did not alter body weight, but it affected consumption of standard food during the time of exposure in all groups. In addition, in adults, HPD produced a decrease in the initial baseline responding in FR1 schedules, an effect that persisted for 4 weeks in males but not in female rats. However, we found that exposure to HPD did not affect resistance to punishment measured by progressive shock strength break points or motivation for food as measured by progressive-ratio break points regardless of sex or age of exposure. Altogether, these results do not provide support for the hypothesis that intermittent exposure to HPD produce persistent increases in the vulnerability to develop addiction-like behaviors towards palatable food.

Aberrant TSC-Rheb axis in Oxytocin receptor+ cells mediate stress-induced anxiety

Stress is a major risk for the onset of several maladaptive processes including pathological anxiety, a diffuse state of heightened apprehension over anticipated threats1. Pathological anxiety is prevalent in up to 59% of patients with Tuberous Sclerosis complex (TSC)2, a neurodevelopmental disorder (NDD) caused by loss-of-function mutations in genes for Tuberin (Tsc2) and/or Hamartin (Tsc1) that together comprise the eponymous protein complex. Here, we generated cell type-specific heterozygous knockout of Tsc2 in cells expressing oxytocin receptor (OTRCs) to model pathological anxiety-like behaviors observed in TSC patient population. The stress of prolonged social isolation induces a sustained negative affective state that precipitates behavioral avoidance, often by aberrant oxytocin signaling in the limbic forebrain3,4. In response to social isolation, there were striking sex differences in stress susceptibility in conditional heterozygote mice when encountering situations of approach-avoidance conflict. Socially isolated male mutants exhibited behavioral avoidance in anxiogenic environments and sought more social interaction for buffering of stress. In contrast, female mutants developed resilience during social isolation and approached anxiogenic environments, while devaluing social interaction. Systemic and medial prefrontal cortex (mPFC)-specific inhibition of downstream effector of TSC, the integrated stress response (ISR), rescued behavioral approach toward anxiogenic environments and conspecifics in male and female mutant mice respectively. Further, we found that Tsc2 deletion in OTRCs leads to OTR-signaling elicited network suppression, i.e., hypofrontality, in male mPFC, which is relieved by inhibiting the ISR. Our findings present evidence in support of a sexually dimorphic role of prefrontal OTRCs in regulating emotional responses in anxiogenic environments, which goes awry in TSC. Our work has broader implications for developing effective treatments for subtypes of anxiety disorders that are characterized by cell-autonomous ISR and prefrontal network suppression.

Fostering wellbeing and healthy lifestyles through conviviality and commensality: Underappreciated benefits of the Mediterranean Diet

Among the often-neglected features of healthy diets, such as the Mediterranean diet, is the preparation and sharing of food, which is (or was) done in a social environment governed by social rules rather than by time constraints. The act of eating is a daily human practice that is not limited to meeting nutritional and energy needs but also involves a constructed social dimension of sharing meals that is part of the process of human civilization and food cultures around the world. In this narrative review, we outline the importance of conviviality in steering part of the health effects of healthful diets, with special reference to the Mediterranean diet. Based on the available evidence, we suggest that public health initiatives (such as nudging to promote conviviality) to improve people's eating and living styles, reduce loneliness, and promote the sharing of meals could improve health. Interventions aimed at directly increasing/improving people's social relationships, networking, and conviviality can-directly and indirectly-improve both psychological well-being and general health.

Loneliness is associated with more trust but worse trustworthiness expectations

Subjective feelings of loneliness emerge due to unsatisfactory social relationships, representing a major risk for mental and physical well-being. Despite its social nature, evidence on how loneliness affects social behaviours and expectations is lacking. Using Bayesian analyses and economic games, we show in three different studies that lonelier individuals trusted their partners to a greater extent despite less favourable trustworthiness expectations, showing a greater discrepancy between their trusting behaviours and their expectations of others' trustworthiness. Such discrepancy was reversed in extravert individuals who also reported to be less lonely. These results provide evidence on two opposing effects of loneliness as a motivator for social connections and promoter of social withdrawal, and demonstrate the moderating role of personality traits. This work contributes to a better understanding of how loneliness impacts social behaviour and social expectations, with important downstream clinical implications for varying health conditions associated with heightened feelings of loneliness.

Oxytocin-Augmented Modular-Based Group Intervention for Loneliness: A Proof-Of-Concept Randomized Controlled Trial

INTRODUCTION

Loneliness poses a significant health problem and existing psychological interventions have shown only limited positive effects on loneliness. Based on preliminary evidence for impaired oxytocin signaling in trait-like loneliness, the current proof-of-concept study used a randomized, double-blind, placebo-controlled design to probe intranasal oxytocin (OT) as an adjunct to a short-term modular-based group intervention for individuals suffering from high trait-like loneliness (HL, UCLA Loneliness Scale ≥55).

METHODS

Seventy-eight healthy HL adults (56 women) received five weekly group psychotherapy sessions. HL participants received OT or placebo before the intervention sessions. Primary outcomes were trait-like loneliness measured at baseline, after the intervention, and again at two follow-up time points (3 weeks and 3 months), and, assessed at each session, state loneliness (visual analog scale), perceived stress (Perceived Stress Scale, PSS-10), quality of life (World Health Organization Five Well-Being Index, WHO-5), and the therapeutic relationship (Group Questionnaire, GQ-D).

RESULTS

The psychological intervention was associated with significantly reduced perceived stress and improved trait-like loneliness across treatment groups, which was still evident at the 3-month follow-up. OT had no significant effect on trait-like loneliness, quality of life, or perceived stress. However, compared to placebo, OT significantly facilitated the decrease in state loneliness within sessions and significantly improved positive bonding between the group members.

CONCLUSION

Despite significantly improved trait-like loneliness after the intervention, OT did not significantly augment this effect. Further studies are needed to determine optimal intervention designs to translate the observed acute effects of OT into long-term benefits.

Effects of social isolation and galactic cosmic radiation on fine motor skills and behavioral performance

Future NASA missions will require astronauts to travel farther and spend longer durations in space than ever before. This will also expose astronauts to longer periods of several physical and psychological challenges, including exposure to space radiation (SR) and periods of social isolation (SI), which could have unknown negative effects on physical and mental health. Each also has the potential to negatively impact sleep which can reduce the ability to cope with stressful experiences and lead to sensorimotor, neurocognitive, and physical deficits. The effects of SI and SR on gross motor performance has been shown to vary, and depend on, individual differences in stress resilience and vulnerability based on our established animal model in which stress produces different effects on sleep. In this study, the impact that SI and SR, either alone or together, had on fine motor skill performance (bilateral tactile adhesive removal task (BTAR)) was assessed in male rats. We also examined emotional, exploratory, and other off-task behavioral responses during testing and assessed whether sensorimotor performance and emotion varied with individual differences in resilience and vulnerability. BTAR task performance was differentially impacted by SI and SR, and were further influenced by the stress resilience/vulnerability phenotype of the rats. These findings further demonstrate that identifying individual responses to stressors that can impact sensorimotor ability and behavior necessary to perform mission-related tasks will be of particular importance for astronauts and future missions. Should similar effects occur in humans, there may be considerable inter-individual variability in the impact that inflight stressors have on astronauts and their ability to perform mission-related tasks.

Ethics of Nudging in the COVID-19 Crisis and the Necessary Return to the Principles of Shared Decision Making: A Critical Review

Nudging, a controversial technique for modifying people's behavior in a predictable way, is claimed to preserve freedom of choice while simultaneously influencing it. Nudging had been largely confined to situations such as promoting healthy eating choices but has been employed in the coronavirus disease 2019 (COVID-19) crisis in a shift towards measures that involve significantly less choice, such as shoves and behavioral prods. Shared decision making (SDM), a method for direct involvement and autonomy, is an alternative approach to communicate risk. Predominantly peer-reviewed scientific publications from standard literature databases like PubMed, PsycInfo, and Psyndex were evaluated in a narrative review. The so-called fear nudges, as well as the dissemination of strongly emotionalizing or moralizing messages can lead to intense psycho-physical stress. The use of these nudges by specialized units during the COVID-19 pandemic generated a societal atmosphere of fear that precipitated a deterioration of the mental and physical health of the population. Major recommendations of the German COVID-19 Snapshot Monitoring (COSMO) study, which are based on elements of nudging and coercive measures, do not comply with ethical principles, basic psychological principles, or evidence-based data. SDM was misused in the COVID-19 crisis, which helped to achieve one-sided goals of governments. The emphasis on utilitarian thinking is criticized and the unethical behavior of decision makers is explained by both using the concept of moral disengagement and the maturity level of coping strategies. There should be a return to an open-ended, democratic, and pluralistic scientific debate without using nudges. It is therefore necessary to return to the origins of SDM.

Disability-related inequalities in the prevalence of loneliness across the lifespan: trends from Australia, 2003 to 2020

BACKGROUND

Experiencing loneliness can be distressing and increasing evidence indicates that being lonely is associated with poor physical and mental health outcomes. Cross-sectional studies have demonstrated that people with disability have increased risk of experiencing loneliness compared to people without disability. However, we do not know if these inequalities have changed over time. This study investigated the prevalence of loneliness for people with disability in Australia annually from 2003 to 2020 to examine whether disability-related inequalities in loneliness have changed over time, and disaggregated results for subgroups of people with disability by age group, sex, and disability group.

METHODS

We used annual data (2003-2020) from the Household, Income and Labour Dynamics in Australia Survey. Loneliness was measured by a single question assessing the subjective experience of loneliness. For each wave, we calculated population-weighted age-standardised estimates of the proportion of people experiencing loneliness for people with and without disability. We then calculated the absolute and relative inequalities in loneliness between people with and without disability for each wave. Analyses were stratified by 10-year age groups, sex, and disability group (sensory or speech, physical, intellectual or learning, psychological, brain injury or stroke, other).

RESULTS

From 2003 to 2020, the prevalence of loneliness was greater for people with disability, such that people with disability were 1.5 to 1.9 times more likely to experience loneliness than people without disability. While the prevalence of loneliness decreased for people without disability between 2003 and 2020, the prevalence of loneliness did not decrease for people with disability during this period. Inequalities in loneliness were more substantial for people with intellectual or learning disabilities, psychological disability, and brain injury or stroke.

CONCLUSION

This study confirms that people with disability have increased risk of loneliness compared to people without disability. We add to the existing evidence by demonstrating that disability-related inequalities in loneliness have persisted for two decades in Australia without improvement. Our findings indicate that addressing inequalities in loneliness for people with disability is a critical public health concern given that loneliness is associated with a wide range of poor health outcomes.

Away from the herd: loneliness as a dysfunction of social alignment

The tendency of all humans to experience loneliness at some point in their lives implies that it serves an adaptive function. Building on biological theories of herding in animals, according to which collective movement emerges from local interactions that are based on principles of attraction, repulsion and alignment, we propose an approach that synthesizes these principles with theories of loneliness in humans. We present here the 'herding model of loneliness' that extends these principles into the psychological domain. We hold that these principles serve as basic building blocks of human interactions and propose that distorted attraction and repulsion tendencies may lead to inability to align properly with others, which may be a core component in loneliness emergence and perpetuation. We describe a neural model of herding in humans and suggest that loneliness may be associated with altered interactions between the gap/error detection, reward signaling, threat and observation-execution systems. The proposed model offers a framework to predict the behavior of lonely individuals and thus may inform intervention designs for reducing loneliness intensity.

CB1R dysfunction of inhibitory synapses in the ACC drives chronic social isolation stress-induced social impairments in male mice

Social isolation is a risk factor for multiple mood disorders. Specifically, social isolation can remodel the brain, causing behavioral abnormalities, including sociability impairments. Here, we investigated social behavior impairment in mice following chronic social isolation stress (CSIS) and conducted a screening of susceptible brain regions using functional readouts. CSIS enhanced synaptic inhibition in the anterior cingulate cortex (ACC), particularly at inhibitory synapses of cholecystokinin (CCK)-expressing interneurons. This enhanced synaptic inhibition in the ACC was characterized by CSIS-induced loss of presynaptic cannabinoid type-1 receptors (CB1Rs), resulting in excessive axonal calcium influx. Activation of CCK-expressing interneurons or conditional knockdown of CB1R expression in CCK-expressing interneurons specifically reproduced social impairment. In contrast, optogenetic activation of CB1R or administration of CB1R agonists restored sociability in CSIS mice. These results suggest that the CB1R may be an effective therapeutic target for preventing CSIS-induced social impairments by restoring synaptic inhibition in the ACC.

Brain evolution and the meaning of catatonia - An update

Back in 2004, in a chapter titled "Brain Evolution and the Meaning of Catatonia", a case was made that the syndrome's core meaning is embedded in millions of years of vertebrate brain evolution. (Fricchione, 2004) In this update, advances over the last almost 20 years, in catatonia theory and research in particular, and pertinent neuropsychiatry in general, will be applied to this question of meaning. The approach will rely heavily on a number of thought leaders, including Nicos Tinbergen, Paul MacLean, John Bowlby, M. Marsel Mesulam, Bruce McEwen and Karl Friston. Their guidance will be supplemented with a selected survey of 21sty century neuropsychiatry, neurophysiology, molecular biology, neuroimaging and neurotherapeutics as applied to the catatonic syndrome. In an attempt to address the question of the meaning of the catatonic syndrome in human life, we will employ two conceptual networks representing the intersubjectivity of the quantitative conceptual network of physical terms and the subjectivity of the qualitative conceptual network of mental and spiritual terms. In the process, a common referent providing extensional identity may emerge (Goodman, 1991). The goal of this exercise is to enhance our attunement with the experience of patients suffering with catatonia. A deeper understanding of catatonia's origins in brain evolution and of the challenges of individual epigenetic development in the setting of environmental events coupled with appreciation of what has been described as the most painful mammalian condition, that of separation, has the potential to foster greater efforts on the part of clinicians to diagnose and treat patients who present with catatonia. In addition, in this ancient and extreme tactic, evolved to provide safety from extreme survival threat, one can speculate what is at the core of human fear and the challenge it presents to all of us. And when the biology, psychology and sociology of catatonia are examined, the nature of solutions to the challenge may emerge.

Characterizing the mechanisms of social connection

Understanding how individuals form and maintain strong social networks has emerged as a significant public health priority as a result of the increased focus on the epidemic of loneliness and the myriad protective benefits conferred by social connection. In this review, we highlight the psychological and neural mechanisms that enable us to connect with others, which in turn help buffer against the consequences of stress and isolation. Central to this process is the experience of rewards derived from positive social interactions, which encourage the sharing of perspectives and preferences that unite individuals. Sharing affective states with others helps us to align our understanding of the world with another's, thereby continuing to reinforce bonds and strengthen relationships. These psychological processes depend on neural systems supporting reward and social cognitive function. Lastly, we also consider limitations associated with pursuing healthy social connections and outline potential avenues of future research.

The role of emotion in eating behavior and decisions

The present paper aims to provide the latest perspectives and future directions on the association between emotions and eating behavior. We discussed individual differences in the impact of negative emotions on eating, emotional eating as disinhibited eating decisions with heightened reward values of and sensitivity to palatable foods in response to negative emotions and social isolation, in addition to emotional eating as maladaptive coping strategies under negative emotion and stress, hedonic (pleasure-oriented) eating decisions mediated by the brain reward system, and self-controlled (health-oriented) eating decisions mediated by the brain control system. Perspectives on future directions were addressed, including the development of early eating phenotypes in infancy, shared neural mechanisms mediated by the ventromedial prefrontal cortex and the dorsolateral prefrontal cortex in emotion and eating decision regulation, possible roles of interoception incorporating hunger and satiety signals, gut microbiome, the insula and the orbitofrontal cortex, and emotional processing capacities in hedonic eating and weight gain.

Enhanced social motivation in briefly isolated male rats

Loneliness and anxiety are associated with psychiatric disorders in humans. Although brief social isolation in adult rats and mice has been proposed as a rodent model of loneliness, its socioemotional characteristics are not well known. In this study, we evaluated the social and emotional behaviors of adult male rats subjected to brief social isolation. Isolated rats frequently showed sniffing behavior toward empty cylinders where conspecifics had previously existed, as well as conspecifics themselves. Furthermore, social motivation correlated with anxiety levels, as indicated by the elevated plus-maze test performance in isolated but not in non-isolated rats. These results suggest that high social motivation is associated with anxiety in briefly isolated rats.

The association between loneliness or social isolation and food and eating behaviours: A scoping review

Loneliness or social isolation and food/eating behaviours have important health consequences and there are rationales for why they could interact. Loneliness and dietary behaviours are recognised as health determinants and targets for interventions at individual, group and population levels. However, there are currently no research reviews investigating associations between these areas. This scoping review synthesized evidence investigating loneliness or social isolation and food/eating behaviours in people aged over 16 years in high-income countries. A systematic search of five databases from 2000 was conducted using predetermined search terms. Dissertation database and backwards citation searches were also conducted. Full text screening of 254 articles/theses resulted in inclusion of three qualitative and 26 quantitative studies, with eight conducted in COVID-19 lockdowns. Almost all studies reported a relationship between loneliness/social isolation and eating behaviours usually considered harmful such as low fruit and vegetable intake and lower diet quality. Qualitative research also supports the detrimental influence of loneliness or social isolation on eating. Study quality was considered, and interpretation and comparison of results was complicated by use of varying methods. Better awareness and understanding of the relationship between these complex aspects of health is needed to inform the development of interventions and practice of nutrition and mental health practitioners, policymakers, researchers and end-users.

Chronic pain patients low in social connectedness report higher pain and need deeper pressure for pain relief

The experience of rejection and disconnection reliably amplifies pain. Yet, little is known about the impact of enduring feelings of closeness, or social connectedness, on experiences of chronic pain. The current secondary analysis tested the hypothesis that greater social connectedness would predict lower chronic pain ratings, mediated by lower depression and anxiety. In addition, based on the social-affective effects of deeper pressure, and our previous finding that deeper pressure from a weighted blanket reduced chronic pain ratings, we examined whether deeper pressure from a weighted blanket would induce greater pain relief in socially disconnected chronic pain patients. We assessed social connectedness, anxiety, and depression at baseline and pain levels before and after a remote, 7-day randomized-controlled trial of a heavy or light (control) weighted blanket in a predominately White (86%) and female (80%) sample of 95 chronic pain patients. Results revealed that lower social connectedness was associated with higher chronic pain ratings, which was mediated by anxiety, but not depression. Pressure level (light vs. deep) moderated associations between social connectedness and pain reductions, such that deeper pressure was necessary for pain relief in the most socially disconnected participants. Our findings suggest a close relationship between social connectedness and chronic pain through a mechanistic pathway of anxiety. Furthermore, our findings demonstrate that sensory-affective interventions such as a weighted blanket may be a beneficial tool for chronic pain sufferers who are prone to social disconnection, potentially by activating embodied representations of safety and social support. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Overlapping representations of food and social stimuli in mouse VTA dopamine neurons

Dopamine neurons of the ventral tegmental area (VTADA) respond to food and social stimuli and contribute to both forms of motivation. However, it is unclear whether the same or different VTADA neurons encode these different stimuli. To address this question, we performed two-photon calcium imaging in mice presented with food and conspecifics and found statistically significant overlap in the populations responsive to both stimuli. Both hunger and opposite-sex social experience further increased the proportion of neurons that respond to both stimuli, implying that increasing motivation for one stimulus increases overlap. In addition, single-nucleus RNA sequencing revealed significant co-expression of feeding- and social-hormone-related genes in individual VTADA neurons. Taken together, our functional and transcriptional data suggest overlapping VTADA populations underlie food and social motivation.

When the Brain Cares: Personal interests amplify engagement of language, self-reference, and reward regions in the brains of children with and without autism

Human language is shaped by individual experiences and interests. However, to study language in the brain, researchers use generic stimuli, avoiding the variable personal interests that typically animate language. Thus, it is unknown how personal interests affect language function in the brain. We conducted personalized functional magnetic resonance imaging (fMRI) in 20 typically-developing children as they listened to personalized narratives about their specific interest and non-personalized, generic narratives. Personally-interesting narratives amplified engagement of language regions, producing more consistent activation patterns across individuals - even though each narrative was unique - than the generic narratives. The personalized narratives also engaged self-reference and reward areas of the brain associated with motivation. Amplification of brain responses to personally-interesting narratives was also observed in 15 autistic children, a condition characterized by both intense specific interests and difficulties with communication. Here we show that personal interests significantly affect language processing in the human brain.

Social networks and the mental health among Chinese older adults: the mediating role of loneliness and moderating role of Internet use

Background

Although a large body of research suggests that social networks from family and friends are important factors in protecting the mental health of older adults, we know little about the mediating and moderating mechanisms behind this relationship. Using China as an example, this study aims to investigate a comprehensive model that includes social networks, loneliness, Internet use, and mental health outcomes in the older population.

Methods

We analyzed data from 7,648 Chinese older people over 60 using the 2018 CLASS survey. We studied how various social networks affect their mental health. Using SPSS's PROCESS macro, we first employed descriptive statistics to examine the characteristics of the participants and calculate the correlations of core variables. Then, we assessed whether loneliness mediated this relationship and tested the moderated mediation effect of Internet use. Our findings shed light on these complex dynamics.

Results

The statistics indicate a positive correlation between social networks and mental health. Furthermore, mediation models revealed that loneliness moderates the relationship between social networks and mental health. In addition, moderated mediation models revealed that Internet use played a distinct function in the family networks model compared to the friend networks model. Internet use moderates explicitly the effects of family networks on loneliness and friend networks on mental health.

Conclusion

The findings emphasize the importance of differentiating the types of social networks to understand their impact on older adults well-being, encouraging policymakers, medical professionals, and families to adopt more targeted approaches when devising policy interventions and medical strategies, especially for older individuals with insufficient social support. Additionally, we urge governments to recognize the varying types of social networks among older populations and harness the protective effects of Internet technology on their well-being within a digital society.

Association of loneliness and grey matter volume in the dorsolateral prefrontal cortex: the mediating role of interpersonal self-support traits

As a social and public health concern, loneliness is associated with an abundance of negative life outcomes such as depressive symptomatology, mortality, and sleep disturbance. Nevertheless, the neural basis underlying loneliness remains elusive; in addition, previous neuroimaging studies about loneliness mainly focused on the elderly and were limited by small sample sizes. Here, utilizing the voxel-based morphometry (VBM) approach via structural magnetic resonance imaging, we investigated the association between brain GMV and loneliness in 462 young adults (67.7% females, age = 18.59 ± 1.14 years). Results from whole-brain VBM analyses revealed that individuals with higher loneliness tended to have greater GMV in the right dorsolateral prefrontal cortex (DLPFC), which was thought to be associated with emotional regulation deficits and executive dysfunction. Importantly, the GMV-based predictive models (a machine-learning method) demonstrated that the correlation between loneliness and GMV in the DLPFC was robust. Further, interpersonal self-support traits (ISS), a Chinese indigenous personality construct and pivotal personality factor for resisting negative life outcomes, mediated the relationship between the GMV in the right DLPFC and loneliness. Taken together, the present study reveals that the GMV in right DLPFC acts as an underlying neurostructural correlate of loneliness in the healthy brain, and further provides a brain-personality-symptom pathway for protection against loneliness in which GMV of DLPFC affects loneliness through ISS traits. Future intervention procedures aiming to decrease loneliness and enhance mental health levels among young adults should be developed through improving interpersonal relationships such as social skills training.

Support from a Best Friend Makes People Eat Less under Stress: Evidence from Two Experiments

When experiencing acute stress, individuals often turn to eating for comfort, as it provides a sense of satiety and satisfaction that can temporarily alleviate the stressful condition. However, this may increase the risk of obesity, diabetes, cardiovascular disease. In this study, we conducted two behavioral experiments to investigate the effectiveness of social support in reducing stress-induced overeating and the mediative role of negative affect and self-efficacy (Experiment 1), as well as the role of reward sensitivity (Experiment 2). Acute stress was induced using a speech preparation task and then participants were asked to regulate their emotions and cognition, either alone or with the help of pictures and supportive sentences provided by a best friend or stranger. Participants in Experiment 1 then completed the food choice task, and participants in Experiment 2 completed the food incentive delay task and the bogus tasting task. The results of both experiments consistently showed that participants who received support from their friends reported lower levels of perceived stress, chose fewer food portions, and consumed fewer snacks during acute stress, compared to the other three groups. Further mediation analysis using the process macro revealed that the differential influence of social support on the choice of high-calorie foods was due to decreased negative affect and increased self-efficacy. This study provides valuable insights for the development of therapeutic interventions for clinical eating disorders.

A quantitative analysis of spontaneous alternation behaviors on a Y-maze reveals adverse effects of acute social isolation on spatial working memory

Animals tend to alternate between different choices, which requires the ability to remember recent choices. The Y-maze spontaneous alternation test is widely used in various animal models for assessing short-term memory, and its precise evaluation depends upon the accurate determination of the arm visit sequence. However, an objective method for defining arm visits is lacking owing to uncertainty regarding the extent to which an animal must go into the arm to be considered visited. Here, we conducted quantitative analyses on mice behavior in the Y-maze while systematically varying the arm visit threshold and assessed the effect of acute social isolation on spatial working memory. Our results revealed that 24-h social isolation significantly reduced spontaneous alternation rate when the arm threshold was set at the distal part of the arm. Furthermore, the memory of the recently visited arms faded away faster in the socially isolated mice. However, other behavioral factors were comparable to those of the group-housed mice, indicating a specific impairment of short-term memory. Our findings suggest that the location of arm visit threshold is critical for the precise evaluation of short-term memory, and our study provides a method for comprehensively and systematically assessing spontaneous alternation behavior in the Y-maze.

The impact of social connectedness on mental health in LGBTQ + identifying individuals during the COVID-19 pandemic in Germany

BACKGROUND

Recent studies report that LGBTQ + people have experienced high levels of mental health problems during COVID-19-related social distancing. Given the well-established association between social isolation and mental health, the main aim of the current study was to investigate differences in mental health and (perceived) social isolation and social support in LGBTQ + individuals compared to heterosexual, cisgender people and to explore whether the hypothesized higher mental health burden in LGBTQ + individuals is (partly) mediated by (perceived) social isolation or social support.

METHODS

N = 531 participants indicating belonging to the LGBTQ + community and N = 1826 not identifying as LGBTQ + participated in a cross-sectional online survey during the initial COVID-19-related lockdown in Germany. Standardized questionnaires were used to assess depression, anxiety, suicidality, loneliness and social support. Further, perceived social isolation and face-to-face communication during the lockdown were assessed.

RESULTS

LGBTQ + people had higher levels of depression, anxiety and suicidal thought, were lonelier and experienced less social support than non-LGBTQ + identifying individuals. Mediation analysis showed that the higher levels of mental health burden in LGBTQ + people were (partly) mediated by reduced social connectedness. Further face-to-face contact positively affected mental health by reducing feelings of loneliness.

CONCLUSION

Given the high impact of loneliness on mental health, governmental actions should be taken to promote social connectedness particularly among LGBTQ + identifying individuals to ensure that the COVID-19 pandemic does not exacerbate the health inequalities that already exist between LGBTQ+-identifying and heterosexual, cisgender people.

A mesocorticolimbic signature of pleasure in the human brain

Pleasure is a fundamental driver of human behaviour, yet its neural basis remains largely unknown. Rodent studies highlight opioidergic neural circuits connecting the nucleus accumbens, ventral pallidum, insula and orbitofrontal cortex as critical for the initiation and regulation of pleasure, and human neuroimaging studies exhibit some translational parity. However, whether activation in these regions conveys a generalizable representation of pleasure regulated by opioidergic mechanisms remains unclear. Here we use pattern recognition techniques to develop a human functional magnetic resonance imaging signature of mesocorticolimbic activity unique to states of pleasure. In independent validation tests, this signature is sensitive to pleasant tastes and affect evoked by humour. The signature is spatially co-extensive with mu-opioid receptor gene expression, and its response is attenuated by the opioid antagonist naloxone. These findings provide evidence for a basis of pleasure in humans that is distributed across brain systems.

Differential effects of social isolation on oligodendrocyte development in different brain regions: insights from a canine model

Social isolation (SI) exerts diverse adverse effects on brain structure and function in humans. To gain an insight into the mechanisms underlying these effects, we conducted a systematic analysis of multiple brain regions from socially isolated and group-housed dogs, whose brain and behavior are similar to humans. Our transcriptomic analysis revealed reduced expression of myelin-related genes specifically in the white matter of prefrontal cortex (PFC) after SI during the juvenile stage. Despite these gene expression changes, myelin fiber organization in PFC remained unchanged. Surprisingly, we observed more mature oligodendrocytes and thicker myelin bundles in the somatosensory parietal cortex in socially isolated dogs, which may be linked to an increased expression of ADORA2A, a gene known to promote oligodendrocyte maturation. Additionally, we found a reduced expression of blood-brain barrier (BBB) structural components Aquaporin-4, Occludin, and Claudin1 in both PFC and parietal cortices, indicating BBB disruption after SI. In agreement with BBB disruption, myelin-related sphingolipids were increased in cerebrospinal fluid in the socially isolated group. These unexpected findings show that SI induces distinct alterations in oligodendrocyte development and shared disruption in BBB integrity in different cortices, demonstrating the value of dogs as a complementary animal model to uncover molecular mechanisms underlying SI-induced brain dysfunction.

Remote, Disconnected, or Detached? Examining the Effects of Psychological Disconnectedness and Cynicism on Employee Performance, Wellbeing, and Work-Family Interface

Owing to the COVID-19 pandemic, organizations worldwide have implemented remote working arrangements that have blurred the work-family boundaries and brought to the forefront employees' sense of disconnectedness from their workplace (i.e., organizational disconnectedness) as a concern for multiple organizational outcomes. Cynicism, a job burnout subdimension, refers to a negative and excessively detached response to relational overload at work. While both workplace disconnectedness and cynicism involve a toxic sense of detachment, they refer to different psychological mechanisms. The present study aims to examine how employee workplace disconnectedness differs from their cynicism, and how both constructs differentially exert their detrimental effects on employee performance, work-family interface, and wellbeing. Using anonymous survey data collected online in 2021 and 2022 from a sample of in-person and flexible workers nested within organizations, conceptual distinctiveness between workplace disconnectedness and cynicism was supported. Measurement invariance across the two groups was supported, and subsequent structural invariance analyses suggested a similar pattern of results for flexible and in-person workers. Specifically, compared to disconnectedness, cynicism exerted higher negative effects on mental health and higher positive effects on cognitive failures and family-to-work conflict. Conversely, compared to cynicism, disconnectedness exerted higher negative effects on performance and work-to-family conflict. That is, feeling indifferent toward others particularly affects mental health and errors, while feeling excluded especially hampers productivity and family life. Theoretical and practical (e.g., inclusive leadership, support groups) implications of these results are discussed in light of the globally rising rates of hybrid work arrangements and related costs for employee wellbeing and productivity.

Understanding the life experiences of elderly in social isolation from the social systems perspective: using Hong Kong as an illustrating example

Aim

The elderly in social isolation often referred to as older people who experience social alienation with little social support from their family, peers, and community suffer from a poor quality of life and well-being. Since their life experiences are affected by a range of factors from different levels, this study seeks to investigate their current life situations and experiences from a social systems perspective.

Methods

A qualitative study was conducted to enrich the understanding of their current life situations and experiences and to generate corresponding practice implications. In this study, there were 13 elderly participants in social isolation, which were users of a social service agency in Hong Kong. They took part in a semi-structured individual interview, sharing their life stories about their daily lives, social relationships, and sense of well-being. Qualitative results were analyzed based on these dimensions.

Results

Results showed that the elderly participants in social isolation had a low level of social support and participation in social activities. Their life experiences and situations were affected by multiple levels of factors that were interrelated.

Conclusion

The results support the application of the social systems perspective in investigating the living conditions of the elderly in social isolation. The corresponding practice implications were also discussed.

Emotions in Times of Pandemic Crisis among Italian Children: A Systematic Review

Several studies underlined the negative effects of forced social isolation on emotional processes in younger population. The current study aimed to review existing evidence of the pandemic's impact on the emotional regulation of Italian children aged 0-12 years in order to identify personal and contextual factors that may adversely impact their developmental process. Different electronic databases (Web of Science, APA PsycInfo, APA PsycArticles, MEDLINE, Psychology and Behavioral Sciences Collection, and Scopus) were used to identify peer-reviewed studies published in English and Italian. Thirteen studies were included in the review, covering a total of 18.843 children. All studies reported negative effects of the lockdown on a child's emotional processes. The most affected were children aged 3-5 years, those living in Northern Italy, and those with low socioeconomic status (SES) families. Alterations in emotional processes were associated with sleep disturbances, quality of family relationships, personality structures, the coping strategies used, and time spent with technological devices. Finally, two- (time × parenting) and three-way (time × parenting × environmental sensitivity) interactions resulted significantly in predicting a child's emotional regulation, respectively, in terms of externalizing and internalizing behaviors. This review remarks that children's emotional processes were negatively impacted during social lockdown, especially where acute social isolation interacted with a set of dispositional and situational risk factors.

Can Inflammation Predict Social Media Use? Linking a Biological Marker of Systemic Inflammation with Social Media Use Among College Students and Middle-Aged Adults

Drawing on recent evidence that inflammation may promote social affiliative motivation, the present research proposes a novel perspective that inflammation may be associated with more social media use. In a cross-sectional analysis of a nationally representative sample, Study 1 (N = 863) found a positive association between C-reactive protein (CRP), a biomarker of systemic inflammation, and the amount of social media use by middle-aged adults. Study 2 (N = 228) showed that among college students CRP was prospectively associated with more social media use 6 weeks later. Providing stronger evidence of the directionality of this effect, Study 3 (N = 171) showed that in college students CRP predicted increased social media use in the subsequent week even after controlling for current week's use. Additionally, in exploratory analyses of CRP and different types of social media use in the same week, CRP was only associated with using social media for social interaction and not for other purposes (e.g., entertainment). The present research sheds light on the social effects of inflammation and highlights potential benefits of using social media as a context for studying the impact of inflammation on social motivation and behavior.

Overlapping representations of food and social stimuli in VTA dopamine neurons

Dopamine neurons of the ventral tegmental area (VTA DA ) respond to food and social stimuli and contribute to both forms of motivation. However, it is unclear if the same or different VTA DA neurons encode these different stimuli. To address this question, we performed 2-photon calcium imaging in mice presented with food and conspecifics, and found statistically significant overlap in the populations responsive to both stimuli. Both hunger and opposite-sex social experience further increased the proportion of neurons that respond to both stimuli, implying that modifying motivation for one stimulus affects responses to both stimuli. In addition, single-nucleus RNA sequencing revealed significant co-expression of feeding- and social-hormone related genes in individual VTA DA neurons. Taken together, our functional and transcriptional data suggest overlapping VTA DA populations underlie food and social motivation.

Homeostatic Regulation of Energetic Arousal During Acute Social Isolation: Evidence From the Lab and the Field

Recent evidence suggests that social contact is a basic need governed by a social homeostatic system. Little is known, however, about how conditions of altered social homeostasis affect human psychology and physiology. Here, we investigated the effects of 8 hr of social isolation on psychological and physiological variables and compared this with 8 hr of food deprivation in a lab experiment (N = 30 adult women). Social isolation led to lowered self-reported energetic arousal and heightened fatigue, comparable with food deprivation. To test whether these findings would extend to a real-life setting, we conducted a preregistered field study during a COVID-19 lockdown (N = 87 adults; 47 women). The drop in energetic arousal after social isolation observed in the lab replicated in the field study for participants who lived alone or reported high sociability, suggesting that lowered energy could be part of a homeostatic response to the lack of social contact.

Will Social Distancing in Service Encounters Affect Consumers' Value Perception During the COVID-19 Pandemic? The Role of Servicescape, Self-Efficacy, and Technological Intervention

This study investigates how physical and psychological distance from one's surroundings may influence one's perception of connectedness with the servicescape and, ultimately, perception of value. It also examines the effect of consumers' techno-psychological differences and interaction modes on this distance-closeness relationship. The researchers develop and test a conceptual framework of how personal cognitive traits and technological intervention may alter consumers' perceived connectedness to the servicescape and influence their perceived value in different service settings. Via a quasi-experiment design in three service scenarios, this research shows a synthetical effect of contactless technology in the distancing setting that may work more effectively on high self-efficiency customers to change their perceived closeness to the servicescape and further change their evaluation of the service. The findings reveal the practical implications of social distancing for different types of consumers in service encounters during or after the COVID-19 pandemic.

Effective interventions to reduce loneliness in big cities

PURPOSE OF REVIEW

Loneliness is a state of distress or discomfort between the desired and experienced level of connectedness to others. These feelings may be particular salient in urban environments that seemingly offer more opportunities for social contact, highlighting the discrepancy. The topic of loneliness has received increased attention because of its negative impact on mental and physical health combined with concerns of increased loneliness due to lockdowns and social distancing regulations during the coronavirus disease 2019 pandemic. We provide a bibliometric and random-effects meta-analysis of clinical trials published since 2020 and available via PubMed.

RECENT FINDINGS

Loneliness interventions have predominantly focused on elderly in the community. Adolescents and young adults as a second group at risk have received much less attention. On average across 44 effect sizes studied in 38 trials, interventions show moderate levels of effectiveness but are characterized by high heterogeneity and trials are often underpowered and use low quality designs. Multidimensional interventions show promise for alleviating loneliness, but the intervention context needs greater attention.

SUMMARY

Scalable and effective interventions for the general population and at-risk groups of loneliness are still scarce. Some promising interventions have been trialled and merit further attention.

Momentary links between adolescents' social media use and social experiences and motivations: Individual differences by peer susceptibility

This longitudinal ecological momentary assessment study examined whether adolescents' use of social media to interact with peers relates to their experiences of social connectedness, social craving, and sensation seeking on an hourly level. Further, we investigated whether these associations differ for adolescents who were nominated by their peers as more or less susceptible to social influences, because highly susceptible youth may be more strongly impacted by social media due to heightened focus on peer behaviors and social feedback. The sample was 212 adolescents in the southeastern United States (Mage = 15 years; range 14 to 17; 56.2% female; 40% White, 28% Latinx, 26% African American, 15% mixed/other race). Controlling for both daily and between-subjects effects, we found a consistent pattern of hourly-level results that were robust to sensitivity analyses. When highly susceptible adolescents used social media to interact with peers in the last hour, they felt less socially connected to others and more strongly craved social connections and novel sensations. Youth who are particularly sensitive to social input from peers may feel less connected to others and crave more connections and exciting stimuli within 1 hr after using social media to interact with peers. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Differential Impact of Social Isolation and Space Radiation on Behavior and Motor Learning in Rats

Future missions to Mars will expose astronauts to several physical and psychological challenges, including exposure to space radiation (SR) and periods of social isolation (SI). Each of these stressors, in addition to mission demands, can affect physical and mental health and potentially negatively impact sleep. The effects of inflight stressors may vary with duration and time course, may be additive or compounding, and may vary with individual differences in stress resilience and vulnerability. Determining how individual differences in resilient and vulnerable phenotypes respond to these mission-related stressors and their interactions with sleep will be crucial for understanding and mitigating factors that can impair performance and damage health. Here, we examined the single and compound effects of ground-based analogs of SI and SR on sensorimotor performance on the balance beam (BB) in rats. We also assessed emotional responses during testing on the BB and assessed whether sensorimotor performance and emotion varied with individual differences in stress resiliency using our established animal model in which stress produces different effects on sleep. Results showed differential motor performance and emotion in the BB task between SI and SR, and these varied based on resilient and vulnerable phenotypes. These findings demonstrate that identifying individual responses to stressors that can impact sensorimotor ability and behavior necessary to perform mission-related tasks will be of particular importance for astronauts and future missions. Should similar effects occur in humans, there may be considerable inter-individual variability in the impact that flight stressors have on the mental health of astronauts and their ability to perform mission-related tasks.

Social interaction, psychotic disorders and inflammation: A triangle of interest

Social interaction difficulties are a hallmark of psychotic disorders, which in some cases can be definitely traced back to autoimmunological causes. Interestingly, systemic and intrathecal inflammation have been shown to significantly influence social processing by increasing sensitivity to threatening social stimuli, which bears some resemblance to psychosis. In this article, we review evidence for the involvement of systemic and intrathecal inflammatory processes in psychotic disorders and how this might help to explain some of the social impairments associated with this group of disorders. Vice versa, we also discuss evidence for the immunomodulatory function of social interactions and their potential role for therapeutic interventions in psychotic disorders.

Hungry for compliments? Ghrelin is not associated with neural responses to social rewards or their pleasantness

The stomach-derived hormone ghrelin motivates food search and stimulates food consumption, with highest plasma concentrations before a meal and lowest shortly after. However, ghrelin also appears to affect the value of non-food rewards such as interaction with rat conspecifics, and monetary rewards in humans. The present pre-registered study investigated how nutritional state and ghrelin concentrations are related to the subjective and neural responses to social and non-social rewards. In a cross-over feed-and-fast design, 67 healthy volunteers (20 women) underwent functional magnetic resonance imaging (fMRI) in a hungry state and after a meal with repeated plasma ghrelin measurements. In task 1, participants received social rewards in the form of approving expert feedback, or non-social computer reward. In task 2, participants rated the pleasantness of compliments and neutral statements. Nutritional state and ghrelin concentrations did not affect the response to social reward in task 1. In contrast, ventromedial prefrontal cortical activation to non-social rewards was reduced when the meal strongly suppressed ghrelin. In task 2, fasting increased activation in the right ventral striatum during all statements, but ghrelin concentrations were neither associated with brain activation nor with experienced pleasantness. Complementary Bayesian analyses provided moderate evidence for a lack of correlation between ghrelin concentrations and behavioral and neural responses to social rewards, but moderate evidence for an association between ghrelin and non-social rewards. This suggests that ghrelin's influence may be restricted to non-social rewards. Social rewards implemented via social recognition and affirmation may be too abstract and complex to be susceptible to ghrelin's influence. In contrast, the non-social reward was associated with the expectation of a material object that was handed out after the experiment. This may indicate that ghrelin might be involved in anticipatory rather than consummatory phases of reward.

Humans have a basic physical and psychological need to move the body: Physical activity as a primary drive

Physical activity, while less necessary for survival in modern times, is still essential for thriving in life, and low levels of movement are related to numerous physical and mental health problems. However, we poorly understand why people move on a day-to-day basis and how to promote greater energy expenditure. Recently, there has been a turn to understand automatic processes with close examination of older theories of behavior. This has co-occurred with new developments in the study of non-exercise activity thermogenesis (NEAT). In this narrative review, it is hypothesized that psycho-physiological drive is important to understand movement in general and NEAT, specifically. Drive, in short, is a motivation state, characterized by arousal and felt tension, energizing the organism to acquire a basic need. Movement is a biological necessity, like food, water, and sleep, but varies across the lifespan and having the greatest impact before adolescence. Movement meets various criteria for a primary drive: (a) deprivation of it produces feelings of tension, such as an urge or craving, known as affectively-charged motivation states, and particularly the feelings of being antsy, restless, hyper or cooped up, (b) provision of the need quickly reduces tension - one can be satiated, and may even over-consume, (c) it can be provoked by qualities of the environment, (d) it is under homeostatic control, (e) there is an appetite (i.e., appetence) for movement but also aversion, and (f) it has a developmental time course. Evidence for drive has mainly come from children and populations with hyperkinetic disorders, such as those with anorexia nervosa, restless legs syndrome, and akathisia. It is also stimulated in conditions of deprivation, such as bed rest, quarantine, long flights, and physical restraint. It seems to be lacking in the hypokinetic disorders, such as depression and Parkinson's. Thus, drive is associated with displeasure and negative reinforcement, subsuming it within the theory of hedonic drive, but it may fit better within new paradigms, such as the WANT model (Wants and Aversions for Neuromuscular Tasks). Recently developed measurement tools, such as the CRAVE scale, may permit the earnest investigation of movement drive, satiation, and motivation states in humans.

Social isolation and the brain: effects and mechanisms

An obvious consequence of the coronavirus disease (COVID-19) pandemic is the worldwide reduction in social interaction, which is associated with many adverse effects on health in humans from babies to adults. Although social development under normal or isolated environments has been studied since the 1940s, the mechanism underlying social isolation (SI)-induced brain dysfunction remains poorly understood, possibly due to the complexity of SI in humans and translational gaps in findings from animal models. Herein, we present a systematic review that focused on brain changes at the molecular, cellular, structural and functional levels induced by SI at different ages and in different animal models. SI studies in humans and animal models revealed common socioemotional and cognitive deficits caused by SI in early life and an increased occurrence of depression and anxiety induced by SI during later stages of life. Altered neurotransmission and neural circuitry as well as abnormal development and function of glial cells in specific brain regions may contribute to the abnormal emotions and behaviors induced by SI. We highlight distinct alterations in oligodendrocyte progenitor cell differentiation and oligodendrocyte maturation caused by SI in early life and later stages of life, respectively, which may affect neural circuit formation and function and result in diverse brain dysfunctions. To further bridge animal and human SI studies, we propose alternative animal models with brain structures and complex social behaviors similar to those of humans.

Customizable, wireless and implantable neural probe design and fabrication via 3D printing

This Protocol Extension describes the low-cost production of rapidly customizable optical neural probes for in vivo optogenetics. We detail the use of a 3D printer to fabricate minimally invasive microscale inorganic light-emitting-diode-based neural probes that can control neural circuit activity in freely behaving animals, thus extending the scope of two previously published protocols describing the fabrication and implementation of optoelectronic devices for studying intact neural systems. The 3D-printing fabrication process does not require extensive training and eliminates the need for expensive materials, specialized cleanroom facilities and time-consuming microfabrication techniques typical of conventional manufacturing processes. As a result, the design of the probes can be quickly optimized, on the basis of experimental need, reducing the cost and turnaround for customization. For example, 3D-printed probes can be customized to target multiple brain regions or scaled up for use in large animal models. This protocol comprises three procedures: (1) probe fabrication, (2) wireless module preparation and (3) implantation for in vivo assays. For experienced researchers, neural probe and wireless module fabrication requires ~2 d, while implantation should take 30-60 min per animal. Time required for behavioral assays will vary depending on the experimental design and should include at least 5 d of animal handling before implantation of the probe, to familiarize each animal to their handler, thus reducing handling stress that may influence the result of the behavioral assays. The implementation of customized probes improves the flexibility in optogenetic experimental design and increases access to wireless probes for in vivo optogenetic research.

Seeing Social: A Neural Signature for Conscious Perception of Social Interactions

Social information is some of the most ambiguous content we encounter in our daily lives, yet in experimental contexts, percepts of social interactions-that is, whether an interaction is present and if so, the nature of that interaction-are often dichotomized as correct or incorrect based on experimenter-assigned labels. Here, we investigated the behavioral and neural correlates of subjective (or conscious) social perception using data from the Human Connectome Project in which participants (n = 1049; 486 men, 562 women) viewed animations of geometric shapes during fMRI and indicated whether they perceived a social interaction or random motion. Critically, rather than experimenter-assigned labels, we used observers' own reports of "Social" or "Non-social" to classify percepts and characterize brain activity, including leveraging a particularly ambiguous animation perceived as "Social" by some but "Non-social" by others to control for visual input. Behaviorally, observers were biased toward perceiving information as social (vs non-social); and neurally, observer reports (compared with experimenter labels) explained more variance in activity across much of the brain. Using "Unsure" reports, we identified several regions that responded parametrically to perceived socialness. Neural responses to social versus non-social content diverged early in time and in the cortical hierarchy. Finally, individuals with higher internalizing trait scores showed both a higher response bias toward "Social" and an inverse relationship with activity in default mode and visual association areas while scanning for social information. Findings underscore the subjective nature of social perception and the importance of using observer reports to study percepts of social interactions.SIGNIFICANCE STATEMENT Simple animations involving two or more geometric shapes have been used as a gold standard to understand social cognition and impairments therein. Yet, experimenter-assigned labels of what is social versus non-social are frequently used as a ground truth, despite the fact that percepts of such ambiguous social stimuli are highly subjective. Here, we used behavioral and fMRI data from a large sample of neurotypical individuals to show that participants' responses reveal subtle behavioral biases, help us study neural responses to social content more precisely, and covary with internalizing trait scores. Our findings underscore the subjective nature of social perception and the importance of considering observer reports in studying behavioral and neural dynamics of social perception.

Social isolation and loneliness among Chinese older adults: Examining aging attitudes as mediators and moderators

Due to labor migration and social changes, the Chinese elderly are facing significant social isolation, along with changes in aging attitudes. However, whether social isolation affects loneliness among the Chinese elderly and whether this relationship is moderated and mediated by aging attitudes is unclear. This empirical study aimed to respond to the above questions in the Chinese context, Based on the data from the 2014 China Longitudinal Aging Social Survey (N = 6,645), the results showed that social isolation is a positive predictor of loneliness; aging attitudes mediate the relationship between social isolation and loneliness. Social isolation affects the loneliness of the elderly partially by weakening positive aging attitudes and strengthening negative aging attitudes; aging attitudes moderate the effect of social isolation on loneliness. For those older adults with higher positive aging attitudes, social isolation has a much smaller effect on loneliness. While for those older adults with higher negative aging attitudes, social isolation has a more substantial effect on their feelings of loneliness. Our results indicate that less social isolation is an effective way to relieve loneliness, and maintaining higher positive aging attitudes and lower negative aging attitudes, is important for the Chinese elderly to prevent loneliness when facing social isolation.