Higher Social Rejection Sensitivity in Opioid-Dependent Patients Is Related to Smaller Insula Gray Matter Volume: A Voxel-Based Morphometric Study

Dissecting shared pain representations to understand their behavioral and clinical relevance

Accounts of shared representations posit that the experience of pain and pain empathy rely on similar neural mechanisms. Experimental research employing novel analytical and methodological approaches has made significant advances in both the identification and targeted manipulation of such shared experiences and their neural underpinnings. This revealed that painful experiences can be shared on different representational levels, from pain-specific to domain-general features, such as negative affect and its regulation. In view of direct links between such representations and social behaviors such as prosocial behavior, conditions characterized by aberrant pain processing may come along with heavy impairments in the social domain, depending on the affected representational level. This has wide potential implications in light of the high prevalence of pain-related clinical conditions, their management, and the overuse of pain medication. In this review and opinion paper, we aim to chart the path toward a better understanding of the link between shared affect and prosocial behavior.

Long-access heroin self-administration induces region specific reduction of grey matter volume and microglia reactivity in the rat

In opioid use disorder (OUD) patients, a decrease in brain grey matter volume (GMV) has been reported. It is unclear whether this is the consequence of prolonged exposure to opioids or is a predisposing causal factor in OUD development. To investigate this, we conducted a structural MRI longitudinal study in NIH Heterogeneous Stock rats exposed to heroin self-administration and age-matched naïve controls housed in the same controlled environment. Structural MRI scans were acquired before (MRI1) and after (MRI2) a prolonged period of long access heroin self-administration resulting in escalation of drug intake. Heroin intake resulted in reduced GMV in various cortical and sub-cortical brain regions. In drug-naïve controls no difference was found between MRI1 and MRI2. Notably, the degree of GMV reduction in the medial prefrontal cortex (mPFC) and the insula positively correlated with the amount of heroin consumed and the escalation of heroin use. In a preliminary gene expression analysis, we identified a number of transcripts linked to immune response and neuroinflammation. This prompted us to hypothesize a link between changes in microglia homeostasis and loss of GMV. For this reason, we analyzed the number and morphology of microglial cells in the mPFC and insula. The number of neurons and their morphology was also evaluated. The primary motor cortex, where no GMV change was observed, was used as negative control. We found no differences in the number of neurons and microglia cells following heroin. However, in the same regions where reduced GMV was detected, we observed a shift towards a rounder shape and size reduction in microglia, suggestive of their homeostatic change towards a reactive state. Altogether these findings suggest that escalation of heroin intake correlates with loss of GMV in specific brain regions and that this phenomenon is linked to changes in microglial morphology.

Long-access heroin self-administration induces region specific reduction of grey matter volume and microglia reactivity in the rat

In opioid use disorder (OUD) patients, a decrease in brain grey matter volume (GMV) has been reported. It is unclear whether this is the consequence of prolonged exposure to opioids or is a predisposing causal factor in OUD development. To investigate this, we conducted a structural MRI longitudinal study in NIH Heterogeneous Stock rats exposed to heroin self-administration and age-matched naïve controls housed in the same controlled environment. Structural MRI scans were acquired before (MRI 1 ) and after (MRI 2 ) a prolonged period of long access heroin self-administration resulting in escalation of drug intake. Heroin intake resulted in reduced GMV in various cortical and sub-cortical brain regions. In drug-naïve controls no difference was found between MRI 1 and MRI 2 . Notably, the degree of GMV reduction in the medial prefrontal cortex (mPFC) and the insula positively correlated with the amount of heroin consumed and the escalation of heroin use. In a preliminary gene expression analysis, we identified a number of transcripts linked to immune response and neuroinflammation. This prompted us to hypothesize a link between changes in microglia homeostasis and loss of GMV. For this reason, we analyzed the number and morphology of microglial cells in the mPFC and insula. The number of neurons and their morphology was also evaluated. The primary motor cortex, where no GMV change was observed, was used as negative control. We found no differences in the number of neurons and microglia cells following heroin. However, in the same regions where reduced GMV was detected, we observed a shift towards a rounder shape and size reduction in microglia, suggestive of their homeostatic change towards a reactive state. Altogether these findings suggest that escalation of heroin intake correlates with loss of GMV in specific brain regions and that this phenomenon is linked to changes in microglial morphology.

Predictors of concurrent heroin use among patients on opioid maintenance treatment in France: a multilevel study over 11 years

BACKGROUND

Consistent reports from health professionals suggest that heroin is commonly used by patients undergoing opioid maintenance treatment (OMT) in France, potentially jeopardizing their recovery process. However, there has been no formal epidemiological assessment on the matter.

METHODS

We use a yearly updated compendium retrieving information on patients admitted in treatment centres in France between 2010 and 2020. Given the hierarchical nature of the data collection, we conduct 2-level modified Poisson regressions to estimate the risks of past month heroin use among patients on OMT.

RESULTS

Despite an overall decreasing trend over time, heroin use among patients on OMT is indeed common, with half of patients declaring concurrent use. Our study unveils differentiated risks of heroin use vary according to the type of OMT, with patients on methadone more likely to use heroin compared to those on buprenorphine. The use of multilevel-related measures also uncovers high heterogeneity among patients' profiles, reflecting different stages in the treatment process, as well as differentiated practices across treatment centres.

CONCLUSION

Opioid maintenance treatment is associated with heroin use, in particular when methadone is involved. The heterogeneity among patients on OMT should be given particular attention, as it underscores the need for tailored interventions.

Distinct dynamic behavioural response to social exclusion in male patients with a history of alcohol dependence

Social exclusion contributes to alcohol consumption, whereas the development of alcohol dependence (AD) can in turn lead to the social exclusion of people with AD. Previous research observed altered neural responses to experimentally induced social exclusion (i.e., Cyberball game) in patients with AD. In addition, inflammation has been associated with both social behaviours and AD. Our study aimed to investigate the dynamic behavioural response and the inflammatory effects of social exclusion in male patients with a history of AD. To this end, we analysed dynamic changes in ball tossing during a partial exclusion Cyberball game and the cytokine interleukin (IL)-1b in saliva in 31 male patients who had a history of AD and 29 gender-matched healthy controls without AD. Participants were included in the first 2 min of the Cyberball game and then excluded by one of the two co-players in the proceeding 5 min. Saliva was collected three times: one before and two after the Cyberball game. Across groups, participants passed the ball more often to the excluder during the partial exclusion period. Analysis using piece-wise linear mixed models showed that patients rapidly increased ball tosses to the excluder upon exclusion, which lasted to the late response phase, whereas the early behavioural response to exclusion took longer for controls. There was no significant change of salivary IL-1b level to exclusion in either patients or controls. The results indicate a distinct dynamic behavioural response to social exclusion in male patients with a history of AD.

Social cognitive neuroscience in the digital age

Human interactions are increasingly taking place from a distance through methods of remote interpersonal communication like video chatting and social media. While remote interpersonal communication has existed for millennia-with the first postal system arising in ∼2400 B.C.-accelerated advances in technology and the recent global COVID-19 pandemic have led to a dramatic increase in remote interpersonal communication use in daily life. Remote interpersonal communication presents a challenge to the field of social-cognitive neuroscience, as researchers seek to understand the implications of various types of remote interpersonal communication for the "social brain." The present paper reviews our current understanding of the social-cognitive neural network and summarizes critical differences between the neural correlates of social cognition in remote vs. face-to-face interactions. In particular, empirical and theoretical work is reviewed that highlight disparities in the neural mechanisms of social perception, evaluation of social stimuli, human motivation, evaluation of social reward, and theory of mind. Potential impacts of remote interpersonal communication on the development of the brain's social-cognitive network are also discussed. Finally, this review closes with future directions for research on social-cognitive neuroscience in our digital technology-connected world and outlines a neural model for social cognition in the context of remote interpersonal communication. For the field of social-cognitive neuroscience to advance alongside of the ever-evolving society, it is crucial for researchers to acknowledge the implications and concepts suggested for future research in this review.

Neural Underpinnings of Social Stress in Substance Use Disorders

BACKGROUND

Drug addiction is a complex brain disorder that is characterized by craving, withdrawal, and relapse, which can be perpetuated by social stress. Stemming from an acute life event, chronic stress, or trauma in a social context, social stress has a major role in the initiation and trajectory of substance use. Preclinical literature shows that early life stress exposure and social isolation facilitate and enhance drug self-administration. Epidemiological evidence links childhood adversity to increased risk for drug use and demonstrates that cumulative stress experiences are predictive of substance use severity in a dose-dependent manner. Stress and drug use induce overlapping brain alterations leading to downregulation or deficits in brain reward circuitry, thereby resulting in greater sensitization to the rewarding properties of drugs. Though stress in the context of addiction has been studied at the neural level, a gap in our understanding of the neural underpinnings of social stress in humans remains.

METHODS

We conducted a systematic review of in vivo structural and functional neuroimaging studies to evaluate the neural processes associated with social stress in individuals with substance use disorder. Results were considered in relation to participants' history of social stress and with regard to the effects of social stress induced during the neuroimaging paradigm.

RESULTS

An exhaustive search yielded 21 studies that matched inclusion criteria. Social stress induces broad structural and functional neural effects in individuals with substance use disorder throughout their lifespan and across drug classes. A few patterns emerged across studies: (1) many of the brain regions altered in individuals who were exposed to chronic social stress and during acute stress induction have been implicated in addiction networks (including the prefrontal cortex, insula, hippocampus, and amygdala); (2) individuals with childhood maltreatment and substance use history had decreased gray matter or activation in regions of executive functioning (including the medial prefrontal cortex, orbitofrontal cortex, anterior cingulate cortex), the hippocampal complex, and the supplementary motor area; and (3) during stress-induction paradigms, activation in the anterior cingulate cortex, caudate, and amygdala was most commonly observed.

CONCLUSIONS/IMPLICATIONS

A distinct overlap is shown between social stress-related circuitry and addiction circuitry, particularly in brain regions implicated in drug-seeking, craving, and relapse. Given the few studies that have thoroughly investigated social stress, the evidence accumulated to date needs to be replicated and extended, particularly using research designs and methods that disentangle the effects of substance use from social stress. Future clinical studies can leverage this information to evaluate the impact of exposure to trauma or adverse life events within substance use research. Expanding knowledge in this emerging field could help clarify neural mechanisms underlying addiction risk and progression to guide causal-experimental inquiry and novel prevention and treatment strategies.

Internalization process of stigma of people with mental illness across cultures: A meta-analytic structural equation modeling approach

This meta-analytic study synthesized findings from 108 independent data sets across 22 cultures to investigate whether the stigma internalization model (the internalization of experienced stigma and perceived stigma to self-stigma) is associated with well-being and recovery of people with mental illness. We also examined the moderating role of collectivism in the internalization process. Results of the meta-analytic structural equation modeling suggested that self-stigma is a significant mediator in the relationships between experienced stigma and perceived stigma with well-being and recovery variables (indirect effects = 0.02 to -0.16). Experienced and perceived stigma had significant direct effects on well-being and recovery variables (Bs = 0.07 to -0.21, p < 0.05), suggesting that both external (e.g., public stigma) and internal (i.e., self-stigma) influences of stigma work concurrently to affect recovery and well-being of people with mental illness. The results of the mixed effect three-level meta-analytic models showed that collectivism significantly moderated the relationship between experienced and perceived stigma with self-stigma (Bs = 0.06 to 0.11, p < 0.05). This implied that the more collectivistic a culture is, the stronger the correlation between experienced and perceived stigma with self-stigma. Implications to stigma reduction approaches were discussed.

Biopsychosocial Model Social Anxiety and Substance Use Revised

PURPOSE OF REVIEW

To review data published in the past 5 years to evaluate the utility of our biopsychosocial model of social anxiety's relation to substance misuse to evaluate the model's utility and update it.

RECENT FINDINGS

Data support the utility of our revised model-e.g., socially anxious persons report using substances to manage subjective anxiety, despite evidence that some substances may not have a direct effect on physiological responding. Other factors with promise include social influence, cognitive processes (e.g., post-event processing), and avoidance. Data highlight the importance of context as socially anxious persons use some substances more in some high-risk situations, despite lack of relation between social anxiety and use generally. Sociocultural factors remain understudied. This updated model is a theory- and data-driven model of the relations between social anxiety and substance misuse that can inform future work to improve substance-related outcomes among this especially vulnerable group.

Substance-Specific and Shared Gray Matter Signatures in Alcohol, Opioid, and Polysubstance Use Disorder

Substance use disorders (SUD) have been shown to be associated with gray matter (GM) loss, particularly in the frontal cortex. However, unclear is to what degree these regional GM alterations are substance-specific or shared across different substances, and if these regional GM alterations are independent of each other or the result of system-level processes at the intrinsic connectivity network level. The T1 weighted MRI data of 65 treated patients with alcohol use disorder (AUD), 27 patients with opioid use disorder (OUD) on maintenance therapy, 21 treated patients with stimulant use disorder comorbid with alcohol use disorder (polysubstance use disorder patients, PSU), and 21 healthy controls were examined via data-driven vertex-wise and voxel-wise GM analyses. Then, structural covariance analyses and open-access fMRI database analyses were used to map the cortical thinning patterns found in the three SUD groups onto intrinsic functional systems. Among AUD and OUD, we identified both common cortical thinning in right anterior brain regions as well as SUD-specific regional GM alterations that were not present in the PSU group. Furthermore, AUD patients had not only the most extended regional thinning but also significantly smaller subcortical structures and cerebellum relative to controls, OUD and PSU individuals. The system-level analyses revealed that AUD and OUD showed cortical thinning in several functional systems. In the AUD group the default mode network was clearly most affected, followed by the salience and executive control networks, whereas the salience and somatomotor network were highlighted as critical for understanding OUD. Structural brain alterations in groups with different SUDs are largely unique in their spatial extent and functional network correlates.