The human amygdala is necessary for developing and expressing normal interpersonal trust

Does rDLPFC activity alter trust? Evidence from a tDCS study

Trust plays an important role in the human economy and people's social lives. Trust is affected by various factors and is related to many brain regions, such as the dorsolateral prefrontal cortex (DLPFC). However, few studies have focused on the impact of the DLPFC on trust through transcranial direct current stimulation (tDCS), although abundant psychology and neuroscience studies have theoretically discussed the possible link between DLPFC activity and trust. In the present study, we aimed to provide evidence of a causal relationship between the rDLPFC and trust behavior by conducting multiple rounds of the classical trust game and applying tDCS over the rDLPFC. We found that overall, anodal stimulation increased trust compared with cathodal stimulation and sham stimulation, while the results in different stages were not completely the same. Our work indicates a causal relationship between rDLPFC excitability and trust behavior and provides a new direction for future research.

The Implications of Moral Neuroscience for Brain Disease: Review and Update

The last 2 decades have seen an explosion of neuroscience research on morality, with significant implications for brain disease. Many studies have proposed a neuromorality based on intuitive sentiments or emotions aimed at maintaining collaborative social groups. These moral emotions are normative, deontological, and action based, with a rapid evaluation of intentionality. The neuromoral circuitry interacts with the basic mechanisms of socioemotional cognition, including social perception, behavioral control, theory of mind, and social emotions such as empathy. Moral transgressions may result from primary disorders of moral intuitions, or they may be secondary moral impairments from disturbances in these other socioemotional cognitive mechanisms. The proposed neuromoral system for moral intuitions has its major hub in the ventromedial prefrontal cortex and engages other frontal regions as well as the anterior insulae, anterior temporal lobe structures, and right temporoparietal junction and adjacent posterior superior temporal sulcus. Brain diseases that affect these regions, such as behavioral variant frontotemporal dementia, may result in primary disturbances of moral behavior, including criminal behavior. Individuals with focal brain tumors and other lesions in the right temporal and medial frontal regions have committed moral violations. These transgressions can have social and legal consequences for the individuals and require increased awareness of neuromoral disturbances among such individuals with brain diseases.

Trust or Distrust: The Effect of Facial Emotion and Trustworthy Behavior on Trust Decision-Making

Based on the model of emotion as social information, this study explores the effects of facial emotions and trustworthy behavior on trust decision-making in trust game through two experiments. The present study used trust game explores the impact of players' facial emotion, arousal and trustworthy behavior on individual trust decision-making through two experiments. The results can be summed up as follows: (1) in the repeated interaction with four players, individuals invest more in trustworthy players than untrustworthy players; (2) individuals invested more in trustworthy players with happy facial emotions, while untrustworthy players with angry facial emotions received less investment. High-arousal facial emotion results in a more extreme investment by the individual; (3) when the players' facial emotion and behavior are inconsistent, the individual will judge according to the player's current behavior, rather than the facial emotion or past behavior.

Every individual makes a difference: A trinity derived from linking individual brain morphometry, connectivity and mentalising ability

Mentalising ability, indexed as the ability to understand others' beliefs, feelings, intentions, thoughts and traits, is a pivotal and fundamental component of human social cognition. However, considering the multifaceted nature of mentalising ability, little research has focused on characterising individual differences in different mentalising components. And even less research has been devoted to investigating how the variance in the structural and functional patterns of the amygdala and hippocampus, two vital subcortical regions of the "social brain", are related to inter-individual variability in mentalising ability. Here, as a first step toward filling these gaps, we exploited inter-subject representational similarity analysis (IS-RSA) to assess relationships between amygdala and hippocampal morphometry (surface-based multivariate morphometry statistics, MMS), connectivity (resting-state functional connectivity, rs-FC) and mentalising ability (interactive mentalisation questionnaire [IMQ] scores) across the participants ( N = 24 $$ N=24 $$ ). In IS-RSA, we proposed a novel pipeline, that is, computing patching and pooling operations-based surface distance (CPP-SD), to obtain a decent representation for high-dimensional MMS data. On this basis, we found significant correlations (i.e., second-order isomorphisms) between these three distinct modalities, indicating that a trinity existed in idiosyncratic patterns of brain morphometry, connectivity and mentalising ability. Notably, a region-related mentalising specificity emerged from these associations: self-self and self-other mentalisation are more related to the hippocampus, while other-self mentalisation shows a closer link with the amygdala. Furthermore, by utilising the dyadic regression analysis, we observed significant interactions such that subject pairs with similar morphometry had even greater mentalising similarity if they were also similar in rs-FC. Altogether, we demonstrated the feasibility and illustrated the promise of using IS-RSA to study individual differences, deepening our understanding of how individual brains give rise to their mentalising abilities.

The neuroanatomy of social trust predicts depression vulnerability

Trust attitude is a social personality trait linked with the estimation of others’ trustworthiness. Trusting others, however, can have substantial negative effects on mental health, such as the development of depression. Despite significant progress in understanding the neurobiology of trust, whether the neuroanatomy of trust is linked with depression vulnerability remains unknown. To investigate a link between the neuroanatomy of trust and depression vulnerability, we assessed trust and depressive symptoms and employed neuroimaging to acquire brain structure data of healthy participants. A high depressive symptom score was used as an indicator of depression vulnerability. The neuroanatomical results observed with the healthy sample were validated in a sample of clinically diagnosed depressive patients. We found significantly higher depressive symptoms among low trusters than among high trusters. Neuroanatomically, low trusters and depressive patients showed similar volume reduction in brain regions implicated in social cognition, including the dorsolateral prefrontal cortex (DLPFC), dorsomedial PFC, posterior cingulate, precuneus, and angular gyrus. Furthermore, the reduced volume of the DLPFC and precuneus mediated the relationship between trust and depressive symptoms. These findings contribute to understanding social- and neural-markers of depression vulnerability and may inform the development of social interventions to prevent pathological depression.

Elevated Neurobehavioral Responses to Negative Social Interactions in Women With Bulimia Nervosa

BACKGROUND

Bulimia nervosa (BN) is a complex psychiatric illness that includes binge-purge behaviors and a belief that one's value as a person depends on body shape and weight. Social pressure strongly influences the development and maintenance of BN, but how this manifests neurobiologically within an individual remains unknown. We used a computational psychiatry approach to evaluate neural mechanisms underlying social interactions in BN.

METHODS

Behavioral and functional magnetic resonance imaging data were collected from 24 women with BN and 26 healthy comparison women using an iterated social exchange game. Data were sorted round by round based on whether the mathematically computed social signals indicated an improving (positive reciprocity) or deteriorating (negative reciprocity) relationship for each participant.

RESULTS

Social interactions with negative reciprocity resulted in more negative behavioral responses and stronger neural activations in both cortical and subcortical regions in women with BN than healthy comparison women. No behavioral or neural differences were observed for interactions demonstrating positive reciprocity, suggesting a very specific form of psychopathology in BN: amplification of negative self-relevant social interactions. Cortical activations (e.g., temporoparietal junction and dorsolateral prefrontal cortex) did not covary with mood symptoms, while subcortical activations (e.g., amygdala and dorsal striatum) were associated with acute psychopathology.

CONCLUSIONS

These data provide a first step toward a mechanistic neuropsychological model of aberrant social processing in BN, demonstrating how a computational psychiatric approach can elucidate neural mechanisms for complex psychiatric illnesses. Future treatments for BN may include targeting neural regions that support these negative biases in social perceptions.

Functional Neuroimaging of Human Hypothalamus in Socioemotional Behavior: A Systematic Review

There exist extensive animal research and lesion studies in humans demonstrating a tight association between the hypothalamus and socioemotional behavior. However, human neuroimaging literature in this direction is still rather limited. In order to reexamine the functional role of this region in regulating human social behavior, we here provided a synthesis of neuroimaging studies showing hypothalamic activation during affiliative, cooperative interactions, and in relation to ticklish laughter and humor. In addition, studies reporting involvement of the hypothalamus during aggressive and antisocial interactions were also considered. Our systematic review revealed a growing number of investigations demonstrating that the evolutionary conserved hypothalamic neural circuity is involved in multiple and diverse aspects of human socioemotional behavior. On the basis of the observed heterogeneity of hypothalamus-mediated socioemotional responses, we concluded that the hypothalamus might play an extended functional role for species survival and preservation, ranging from exploratory and approaching behaviors promoting social interactions to aggressive and avoidance responses protecting and defending the established social bonds.

Loneliness and the Social Brain: How Perceived Social Isolation Impairs Human Interactions

Loneliness is a painful condition associated with increased risk for premature mortality. The formation of new, positive social relationships can alleviate feelings of loneliness, but requires rapid trustworthiness decisions during initial encounters and it is still unclear how loneliness hinders interpersonal trust. Here, a multimodal approach including behavioral, psychophysiological, hormonal, and neuroimaging measurements is used to probe a trust-based mechanism underlying impaired social interactions in loneliness. Pre-stratified healthy individuals with high loneliness scores (n = 42 out of a screened sample of 3678 adults) show reduced oxytocinergic and affective responsiveness to a positive conversation, report less interpersonal trust, and prefer larger social distances compared to controls (n = 40). Moreover, lonely individuals are rated as less trustworthy compared to controls and identified by the blinded confederate better than chance. During initial trust decisions, lonely individuals exhibit attenuated limbic and striatal activation and blunted functional connectivity between the anterior insula and occipitoparietal regions, which correlates with the diminished affective responsiveness to the positive social interaction. This neural response pattern is not mediated by loneliness-associated psychological symptoms. Thus, the results indicate compromised integration of trust-related information as a shared neurobiological component in loneliness, yielding a reciprocally reinforced trust bias in social dyads.

Amygdala hyperconnectivity in the paranoid state: A transdiagnostic study

BACKGROUND

Paranoia significantly contributes to social impairments across clinical diagnoses, and amygdala dysfunction has been identified as a neurobiological marker of paranoia among individuals with schizophrenia. Therefore, we aimed to investigate amygdala functional connectivity (FC) in paranoia across diagnoses.

METHODS

Forty-five patients with recent history of clinically significant paranoid ideation and a current DSM-5 diagnosis of any disorder underwent resting-state functional magnetic resonance imaging either in a paranoid (N = 23) or non-paranoid (N = 22) state. Amygdala FC were compared between paranoid and non-paranoid patients. Supplemental correlation analyses between amygdala FC and paranoia score were performed separately in patients and a non-equivalent healthy control (HC; N = 60) group.

RESULTS

Increased FC was found between right amygdala and the prefrontal cortex (PFC) [bilateral medial superior frontal gyrus, anterior cingulate, medial frontal gyrus, the triangular part and the opercular part of the inferior frontal gyrus (IFG); right orbital part of IFG], the frontal cortex (bilateral median cingulate, left precentral gyrus), and subcortical areas (right insula) in the paranoid group compared with the non-paranoid group. No significant between-group differences were observed in left amygdala FC. FC between right amygdala and PFC and frontal cortex was positively correlated with paranoia in patient and HC groups.

CONCLUSION

Paranoia is associated with right amygdala hyperconnectivity with PFC, frontal cortex, and insula. This hyperconnectivity was evident regardless of diagnosis and therefore identify a likely transdiagnostic neural mechanism, which may help to identify treatment targets that could potentially improve the social functioning of individuals with clinical diagnoses.

Hierarchical Neural Prediction of Interpersonal Trust

Exploring neural markers that predict trust behavior may help us to identify the cognitive process underlying trust decisions and to develop a new approach to promote interpersonal trust. It remains unknown how trust behavior may be predicted early in the decision process. We used electrophysiology to sample the brain activity while participants played the role of trustor in an iterative trust game. The results showed that during the trust generation stage, the trust condition led to higher frontocentral beta band activity related to cognitive inhibition compared to the distrust condition (item level). Moreover, individuals with higher frontocentral beta band activity were more likely to perform trust choices at the single-trial level (individual level). Furthermore, after receiving reciprocity feedback on trial_n-1, compared to the betrayal feedback and the distrust choice, the frontocentral beta band oscillation had a stronger predictive effect regarding trust choices on trial_n. These findings indicate that beta band oscillations during the decision generation stage contribute to subsequent trust choices.

Increased ethanol intake is associated with social anxiety in offspring exposed to ethanol on gestational day 12

Prenatal alcohol exposure (PAE) can result in physical, cognitive, and neurological deficits termed Fetal Alcohol Spectrum Disorder (FASD). Deficits in social functioning associated with PAE are frequently observed and persist throughout the lifespan. Social impairments, such as social anxiety, are associated with increased alcohol abuse, which is also highly pervasive following PAE. Yet, the relationship between PAE-induced social alterations and alcohol intake later in life is not well understood. In order to test this relationship, we exposed pregnant female Sprague Dawley rats to a single instance of PAE on gestational day 12, a period of substantial neural development, and tested offspring in adulthood (postnatal day 63) in a modified social interaction test followed by alternating alone and social ethanol intake sessions. Consistent with our previous findings, we found that, in general, PAE reduced social preference (measure of social anxiety-like behavior) in female but not male adults. However, ethanol intake was significantly higher in the PAE group regardless of sex. When dividing subjects according to level of social anxiety-like behavior (low, medium, or high), PAE males (under both drinking contexts) and control females (under the social drinking context) with a high social anxiety phenotype showed the highest level of ethanol intake. Taken together, these data indicate that PAE differentially affects the interactions between social anxiety, ethanol intake, and drinking context in males and females. These findings extend our understanding of the complexity and persistence of PAE's sex-dependent effects into adulthood.

Left Amygdala and Putamen Activation Modulate Emotion Driven Decisions in the Iterated Prisoner's Dilemma Game

Although economic decision-making is commonly characterized as a purely rational phenomenon, it is clear that real-world decision-making is influenced by emotions. Yet, relatively little is known about the neural correlates of this process. To explore this issue, 20 participants underwent fMRI scanning while engaged in the Prisoner's Dilemma game under partner-directed sympathy, anger and neutral emotion conditions. Participants were most and least likely to cooperate after sympathy and anger induction, respectively, with the neutral condition eliciting intermediate cooperation rates. Moreover, the sympathy condition elicited quicker responses for cooperation than defection choices, whereas this pattern was reversed in the anger and neutral conditions. Left amygdala activation showed a positive correlation with cooperation rates and self-reports of partner directed sympathy in the sympathy condition. In the anger condition, left putamen activation was positively correlated with cooperation rates and negatively correlated with self-reports of partner directed anger strength. These findings indicate that while the left amygdala activation may be indicative of emotion enhancement and increase of cooperative behavior, the left putamen may help to suppress an emotion to overcome anger and engage in cooperation.

Relationship between trust in neighbors and regional brain volumes in a population-based study

Trust is a fundamental part of human interpersonal relationships, and among other complex factors it is shown to be linked with demographic characteristics and specific regions of the brain. The authors utilized a large, community-based database gathered from the Dallas Heart Study to determine specific brain regions associated with an individual's trust in neighbors. A trust questionnaire was taken and regional brain volumes were determined from structural magnetic resonance imaging. Two analyses using logistic regressions in a training set and validation set were performed to investigate the association between measures of trust and bilateral brain region volumes and thickness. A total of 1527 participants were included in the final analysis. Right caudal anterior cingulate cortex thickness and left caudate volume were inversely correlated with neighbor trust, while left amygdala volume was positively correlated with neighbor trust. Greater age and higher level of education were positively correlated with neighbor trust. African Americans showed less neighbor trust than Caucasians and Hispanics. Anterior cingulate cortex, caudate, and amygdala are all integral parts of the salience network; thus, results of this study suggest that the salience network, the brain network responsible for functions such as communication and social behavior, may play a role in the formation of interpersonal trust.

Connectome-based model predicts individual differences in propensity to trust

Trust constitutes a fundamental basis of human society and plays a pivotal role in almost every aspect of human relationships. Although enormous interest exists in determining the neuropsychological underpinnings of a person's propensity to trust utilizing task-based fMRI; however, little progress has been made in predicting its variations by task-free fMRI based on whole-brain resting-state functional connectivity (RSFC). Here, we combined a one-shot trust game with a connectome-based predictive modeling approach to predict propensity to trust from whole-brain RSFC. We demonstrated that individual variations in the propensity to trust were primarily predicted by RSFC rooted in the functional integration of distributed key nodes-caudate, amygdala, lateral prefrontal cortex, temporal-parietal junction, and the temporal pole-which are part of domain-general large-scale networks essential for the motivational, affective, and cognitive aspects of trust. We showed, further, that the identified brain-behavior associations were only evident for trust but not altruistic preferences and that propensity to trust (and its underlying neural underpinnings) were modulated according to the extent to which a person emphasizes general social preferences (i.e., horizontal collectivism) rather than general risk preferences (i.e., trait impulsiveness). In conclusion, the employed data-driven approach enables to predict propensity to trust from RSFC and highlights its potential use as an objective neuromarker of trust impairment in mental disorders.

Oxytocin Facilitates Social Learning by Promoting Conformity to Trusted Individuals

There is considerable interest in the role of the neuropeptide oxytocin in promoting social cohesion both in terms of promoting specific social bonds and also more generally for increasing our willingness to trust others and/or to conform to their opinions. These latter findings may also be important in the context of a modulatory role for oxytocin in improving the efficacy of behavioral therapy in psychiatric disorders. However, the original landmark studies claiming an important role for oxytocin in enhancing trust in others, primarily using economic game strategies, have been questioned by subsequent meta-analytic approaches or failure to reproduce findings in different contexts. On the other hand, a growing number of studies have consistently reported that oxytocin promotes conformity to the views of groups of in-group individuals. Most recently we have found that oxytocin can increase acceptance of social advice given by individual experts without influencing their perceived trustworthiness per se, but that increased conformity in this context is associated with how much an expert is initially trusted and liked. Oxytocin can also enhance the impact of information given by experts by facilitating expectancy and placebo effects. Here we therefore propose that a key role for oxytocin is not in facilitating social trust per se but in conforming to, and learning from, trusted individuals who are either in-group members and/or perceived experts. The implications of this for social learning and use of oxytocin as an adjunct to behavioral therapy in psychiatric disorders are discussed. Interpersonal trust within social groups is of key importance for social interactions, bonds, cooperation and learning and trust between different groups can also help ensure a stable and peaceful co-existence as well as mutually beneficial co-operation and trade. Trust is generally considered to be critical for co-operation and reciprocity in social and economic interactions but importantly trust also involves risk of potential injury if misplaced or broken and we have a natural aversion to taking such risks (Hardin, 2002; Ostrom and Walker, 2003). Indeed, an important factor influencing our trust behavior is that we are strongly motivated to avoid others betraying our trust (Bohnet and Zeckhauser, 2004; Bohnet et al., 2008). Trust can potentially be influenced by our assessment of the level of risk that trusting others might have and also by increased sensitivity to physical and/or other cues for detecting trustworthiness. It is therefore of great importance to identify both behavioral and physiological factors which can act to enhance trust, particularly in situations where individuals have impaired trust and therefore find it hard to interact socially with others and learn from them and/or to benefit optimally from cognitive and behavioral therapeutic strategies.

Association of the oxytocin receptor gene with attitudinal trust: role of amygdala volume

Previous studies have shown that genetic variations in rs53576, a common variant of the oxytocin receptor gene (OXTR) resulting from a single nucleotide polymorphism involving an adenine (A)/guanine (G) transition, are associated with attitudinal trust in men. However, the pathway from gene to behaviour has not been elucidated. We conducted the present study to determine whether amygdala volume mediates the association between OXTR rs53576 genotypes and attitudinal trust. Our results revealed that the left amygdala volume was significantly smaller in GG men than in AA and AG men, whereas it was significantly smaller in AA and AG women than in GG women. In addition, the left amygdala volume was negatively associated with attitudinal trust in men, whereas there was no such association in women. We also found a significant mediation effect of the left amygdala volume on the association between OXTR rs53576 genotypes and attitudinal trust in men. The results of our study suggest that the left amygdala volume plays a pivotal role in the association between OXTR rs53576 genotypes and attitudinal trust in men.

Amygdala Represents Diverse Forms of Intangible Knowledge, That Illuminate Social Processing and Major Clinical Disorders

Amygdala is an intensively researched brain structure involved in social processing and multiple major clinical disorders, but its functions are not well understood. The functions of a brain structure are best hypothesized on the basis of neuroanatomical connectivity findings, and of behavioral, neuroimaging, neuropsychological and physiological findings. Among the heaviest neuroanatomical interconnections of amygdala are those with perirhinal cortex (PRC), but these are little considered in the theoretical literature. PRC integrates complex, multimodal, meaningful and fine-grained distributed representations of objects and conspecifics. Consistent with this connectivity, amygdala is hypothesized to contribute meaningful and fine-grained representations of intangible knowledge for integration by PRC. Behavioral, neuroimaging, neuropsychological and physiological findings further support amygdala mediation of a diversity of such representations. These representations include subjective valence, impact, economic value, noxiousness, importance, ingroup membership, social status, popularity, trustworthiness and moral features. Further, the formation of amygdala representations is little understood, and is proposed to be often implemented through embodied cognition mechanisms. The hypothesis builds on earlier work, and makes multiple novel contributions to the literature. It highlights intangible knowledge, which is an influential but insufficiently researched factor in social and other behaviors. It contributes to understanding the heavy but neglected amygdala-PRC interconnections, and the diversity of amygdala-mediated intangible knowledge representations. Amygdala is a social brain region, but it does not represent species-typical social behaviors. A novel proposal to clarify its role is postulated. The hypothesis is also suggested to illuminate amygdala's involvement in several core symptoms of autism spectrum disorder (ASD). Specifically, novel and testable explanations are proposed for the ASD symptoms of disorganized visual scanpaths, apparent social disinterest, preference for concrete cognition, aspects of the disorder's heterogeneity, and impairment in some activities of daily living. Together, the presented hypothesis demonstrates substantial explanatory potential in the neuroscience, social and clinical domains.

Heart rate variability is associated with social value orientation in males but not females

Phylogenetic and neurobiological theories suggest that inter-individual differences in high frequency heart rate variability (HF-HRV) are associated with inter-individual differences in social behavior and social cognition. To test these theories, we investigated whether individuals with high and low HF-HRV would show different preferences for cooperative behavior in social contexts. We recorded resting state HF-HRV in 84 healthy individuals before they completed the Social Value Orientation task, a well-established measure of cooperative preferences. HF-HRV was derived from short-term (300 s) and ultra-short-term (60 s, 120 s) recordings of participants’ heart rate to determine the robustness of possible findings. Irrespective of recording length, we found a sex-dependent association between inter-individual differences in HF-HRV and inter-individual differences in social value orientation: The preference for cooperation was more pronounced among individuals with high as compared low HF-HRV, albeit only in male and not in female participants. These findings suggest that males with high HF-HRV are more inclined to engage in cooperative behavior than males with low HF-HRV.

Dissociable contributions of the prefrontal cortex in group-based cooperation

The success of our political institutions, environmental stewardship and evolutionary fitness all hinge on our ability to prioritize collective-interest over self-interest. Despite considerable interest in the neuro-cognitive processes that underlie group cooperation, the evidence to date is inconsistent. Several papers support models of prosocial restraint, while more recent work supports models of prosocial intuition. We evaluate these competing models using a sample of lesion patients with damage to brain regions previously implicated in intuition and deliberation. Compared to matched control participants (brain damaged and healthy controls), we found that patients with dorsolateral prefrontal cortex (dlPFC) damage were less likely to cooperate in a modified public goods game, whereas patients with ventromedial prefrontal cortex (vmPFC) damage were more likely to cooperate. In contrast, we observed no association between cooperation and amygdala damage relative to controls. These findings suggest that the dlPFC, rather than the vmPFC or amygdala, plays a necessary role in group-based cooperation. These findings suggest cooperation does not solely rely on intuitive processes. Implications for models of group cooperation are discussed.

The Role of the Amygdala in Facial Trustworthiness Processing: A Systematic Review and Meta-Analyses of fMRI Studies

Background

Faces play a key role in signaling social cues such as signals of trustworthiness. Although several studies identify the amygdala as a core brain region in social cognition, quantitative approaches evaluating its role are scarce.

Objectives

This review aimed to assess the role of the amygdala in the processing of facial trustworthiness, by analyzing its amplitude BOLD response polarity to untrustworthy versus trustworthy facial signals under fMRI tasks through a Meta-analysis of effect sizes (MA). Activation Likelihood Estimation (ALE) analyses were also conducted.

Data sources

Articles were retrieved from MEDLINE, ScienceDirect and Web-of-Science in January 2016. Following the PRISMA statement guidelines, a systematic review of original research articles in English language using the search string “(face OR facial) AND (trustworthiness OR trustworthy OR untrustworthy OR trustee) AND fMRI” was conducted.

Study selection and data extraction

The MA concerned amygdala responses to facial trustworthiness for the contrast Untrustworthy vs. trustworthy faces, and included whole-brain and ROI studies. To prevent potential bias, results were considered even when at the single study level they did not survive correction for multiple comparisons or provided non-significant results. ALE considered whole-brain studies, using the same methodology to prevent bias. A summary of the methodological options (design and analysis) described in the articles was finally used to get further insight into the characteristics of the studies and to perform a subgroup analysis. Data were extracted by two authors and checked independently.

Data synthesis

Twenty fMRI studies were considered for systematic review. An MA of effect sizes with 11 articles (12 studies) showed high heterogeneity between studies [Q(11) = 265.68, p < .0001; I² = 95.86%, 94.20% to 97.05%, with 95% confidence interval, CI]. Random effects analysis [RE(183) = 0.851, .422 to .969, 95% CI] supported the evidence that the (right) amygdala responds preferentially to untrustworthy faces. Moreover, two ALE analyses performed with 6 articles (7 studies) identified the amygdala, insula and medial dorsal nuclei of thalamus as structures with negative correlation with trustworthiness. Six articles/studies showed that posterior cingulate and medial frontal gyrus present positive correlations with increasing facial trustworthiness levels. Significant effects considering subgroup analysis based on methodological criteria were found for experiments using spatial smoothing, categorization of trustworthiness in 2 or 3 categories and paradigms which involve both explicit and implicit tasks.

Limitations

Significant heterogeneity between studies was found in MA, which might have arisen from inclusion of studies with smaller sample sizes and differences in methodological options. Studies using ROI analysis / small volume correction methods were more often devoted specifically to the amygdala region, with some results reporting uncorrected p-values based on mainly clinical a priori evidence of amygdala involvement in these processes. Nevertheless, we did not find significant evidence for publication bias.

Conclusions and implications of key findings

Our results support the role of amygdala in facial trustworthiness judgment, emphasizing its predominant role during processing of negative social signals in (untrustworthy) faces. This systematic review suggests that little consistency exists among studies’ methodology, and that larger sample sizes should be preferred.

Parkinson Patients' Initial Trust in Avatars: Theory and Evidence

Parkinson's disease (PD) is a neurodegenerative disease that affects the motor system and cognitive and behavioral functions. Due to these impairments, PD patients also have problems in using the computer. However, using computers and the Internet could help these patients to overcome social isolation and enhance information search. Specifically, avatars (defined as virtual representations of humans) are increasingly used in online environments to enhance human-computer interaction by simulating face-to-face interaction. Our laboratory experiment investigated how PD patients behave in a trust game played with human and avatar counterparts, and we compared this behavior to the behavior of age, income, education and gender matched healthy controls. The results of our study show that PD patients trust avatar faces significantly more than human faces. Moreover, there was no significant difference between initial trust of PD patients and healthy controls in avatar faces, while PD patients trusted human faces significantly less than healthy controls. Our data suggests that PD patients' interaction with avatars may constitute an effective way of communication in situations in which trust is required (e.g., a physician recommends intake of medication). We discuss the implications of these results for several areas of human-computer interaction and neurological research.

Oxytocin and Social Cognitions in Schizophrenia: A Systematic Review

Schizophrenia is a chronic multifactorial disorder. Over the last years, there has been a growing interest in cognitive deficits in schizophrenia, which is considered by many as the core abnormality of the disease. In the systematic review we focus on the social cognition and its correlation with the neuropeptide oxytocin, which is shown to be involved in the emotion recognizing processes, in the trust behavior and many other aspects of social functioning. The systematic review was performed in order to summarize the data on the liaison of oxytocin with the social cognition impairment in schizophrenia patients. Oxytocin is assumed to be a potential therapeutic agent for schizophrenia, with a special link to social cognitive functions. The oxytocinergic system is a promising neuromodulator of emotion recognition that may have the potential to normalize the social dysfunction seen in schizophrenia. Further studies are required to provide more data on the correlations between oxytocin and socialcognition as well as other schizophrenia symptoms.

How do we trust strangers? The neural correlates of decision making and outcome evaluation of generalized trust

This study investigates the brain correlates of decision making and outcome evaluation of generalized trust (i.e. trust in unfamiliar social agents)-a core component of social capital which facilitates civic cooperation and economic exchange. We measured 18 (9 male) Chinese participants' event-related potentials while they played the role of the trustor in a one-shot trust game with unspecified social agents (trustees) allegedly selected from a large representative sample. At the decision-making phase, greater N2 amplitudes were found for trustors' distrusting decisions compared to trusting decisions, which may reflect greater cognitive control exerted to distrust. Source localization identified the precentral gyrus as one possible neuronal generator of this N2 component. At the outcome evaluation phase, principal components analysis revealed that the so called feedback-related negativity was in fact driven by a reward positivity, which was greater in response to gain feedback compared to loss feedback. This reduced reward positivity following loss feedback may indicate that the absence of reward for trusting decisions was unexpected by the trustor. In addition, we found preliminary evidence suggesting that the decision-making processes may differ between high trustors and low trustors.

Representation of economic preferences in the structure and function of the amygdala and prefrontal cortex

Social value orientations (SVOs) are economic preferences for the distribution of resources - prosocial individuals are more cooperative and egalitarian than are proselfs. Despite the social and economic implications of SVOs, no systematic studies have examined their neural correlates. We investigated the amygdala and dorsolateral prefrontal cortex (DLPFC) structures and functions in prosocials and proselfs by functional magnetic resonance imaging and evaluated cooperative behavior in the Prisoner's Dilemma game. We found for the first time that amygdala volume was larger in prosocials and positively correlated with cooperation, while DLPFC volume was larger in proselfs and negatively correlated with cooperation. Proselfs' decisions were marked by strong DLPFC and weak amygdala activity, and prosocials' decisions were marked by strong amygdala activity, with the DLPFC signal increasing only in defection. Our findings suggest that proselfs' decisions are controlled by DLPFC-mediated deliberative processes, while prosocials' decisions are initially guided by automatic amygdala processes.

Polymorphism of the Oxytocin Receptor Gene Modulates Behavioral and Attitudinal Trust among Men but Not Women

A relationship between the oxytocin receptor gene (OXTR) and behavioral and attitudinal trust has been suggested, but the nature of this relationship has not yet been established. We obtained behavioral trust data from 470 Japanese participants (242 women) aged 20–59 years, together with their levels of general trust and personality traits (NEO-FFI). Saliva buccal swabs were collected from 411 of these 470 participants and used for genotyping of OXTR rs53576. Our participants were found to have more AA alleles (40%) than GG alleles (12%). The GG men were more trusting and also rated higher on attitudinal trust than AA men, and this difference did not diminish when personality traits were controlled for. However, this pattern was not observed among women. In addition, controlling for attitudinal trust reduced the difference in behavioral trust among men to a non-significant level, but the difference in attitudinal trust remained significant when behavioral trust was controlled. These results indicate that the OXTR genotype affects attitudinal trust as part of an individual’s relatively stable disposition, and further affects behavioral trust through changes in attitudinal trust.

Neural Responses to Truth Telling and Risk Propensity under Asymmetric Information

Trust is multi-dimensional because it can be characterized by subjective trust, trust antecedent, and behavioral trust. Previous research has investigated functional brain responses to subjective trust (e.g., a judgment of trustworthiness) or behavioral trust (e.g., decisions to trust) in perfect information, where all relevant information is available to all participants. In contrast, we conducted a novel examination of the patterns of functional brain activity to a trust antecedent, specifically truth telling, in asymmetric information, where one individual has more information than others, with the effect of varying risk propensity. We used functional magnetic resonance imaging (fMRI) and recruited 13 adults, who played the Communication Game, where they served as the "Sender" and chose either truth telling (true advice) or lie telling (false advice) regarding the best payment allocation for their partner. Our behavioral results revealed that subjects with recreational high risk tended to choose true advice. Moreover, fMRI results yielded that the choices of true advice were associated with increased cortical activation in the anterior rostral medial and frontopolar prefrontal cortices, middle frontal cortex, temporoparietal junction, and precuneus. Furthermore, when we specifically evaluated a role of the bilateral amygdala as the region of interest (ROI), decreased amygdala response was associated with high risk propensity, regardless of truth telling or lying. In conclusion, our results have implications for how differential functions of the cortical areas may contribute to the neural processing of truth telling.

Damage to the insula is associated with abnormal interpersonal trust

Reciprocal trust is a crucial component of cooperative, mutually beneficial social relationships. Previous research using tasks that require judging and developing interpersonal trust has suggested that the insula may be an important brain region underlying these processes (King-Casas et al., 2008). Here, using a neuropsychological approach, we investigated the role of the insula in reciprocal trust during the Trust Game (TG), an interpersonal economic exchange. Consistent with previous research, we found that neurologically normal adults reciprocate trust in kind, i.e., they increase trust in response to increases from their partners, and decrease trust in response to decreases. In contrast, individuals with damage to the insula displayed abnormal expressions of trust. Specifically, these individuals behaved benevolently (expressing misplaced trust) when playing the role of investor, and malevolently (violating their partner's trust) when playing the role of the trustee. Our findings lend further support to the idea that the insula is important for expressing normal interpersonal trust, perhaps because the insula helps to recognize risk during decision-making and to identify social norm violations.

The tendency to trust is reflected in human brain structure

Trust is an important component of human social life. Within the brain, the function within a neural network implicated in interpersonal and social-cognitive processing is associated with the way trust-based decisions are made. However, it is currently unknown how localized structure within the healthy human brain is associated with the tendency to trust other people. This study was designed to test the prediction that individual differences in the tendency to trust are associated with regional gray matter volume within the ventromedial prefrontal cortex (vmPFC), amygdala and anterior insula. Behavioral and neuroimaging data were collected from a sample of 82 healthy participants. Individual differences in the tendency to trust were measured in two ways (self-report and behaviorally: trustworthiness evaluation of faces task). Voxel based morphometry analyses of high-resolution structural images (VBM8-DARTEL) were conducted to test for the association between the tendency to trust and regional gray matter volume. The results provide converging evidence that individuals characterized as trusting others more exhibit increased gray matter volume within the bilateral vmPFC and bilateral anterior insula. Greater right amygdala volume is associated with the tendency to rate faces as more trustworthy and distrustworthy (U-shaped function). A whole brain analysis also shows that the tendency to trust is reflected in the structure of dorsomedial prefrontal cortex. These findings advance neural models that associate the structure and function of the human brain with social decision-making and the tendency trust other people.

Chill-inducing music enhances altruism in humans

Music is a universal feature of human cultures, and it has both fascinated and troubled many researchers. In this paper we show through the dictator game (DG) that an individual’s listening to preferred “chill-inducing” music may promote altruistic behavior that extends beyond the bounds of kin selection or reciprocal altruism. Participants were 22 undergraduate and postgraduate students who were divided into two groups, the in-group and the out-group, and they acted as dictators. The dictators listened to their own preferred “chill-inducing” music, to music they disliked, or to silence, and then played the DG. In this hypothetical experiment, the dictators were given real money (which they did not keep) and were asked to distribute it to the recipients, who were presented as stylized images of men and women displayed on a computer screen. The dictators played the DG both before and after listening to the music. Both male and female dictators gave more money after listening to their preferred music and less after listening to the music they disliked, whereas silence had no effect on the allocated amounts. The group to which the recipient belonged did not influence these trends. The results suggest that listening to preferred “chill-inducing” music promotes altruistic behavior.

The amygdala as a hub in brain networks that support social life

A growing body of evidence suggests that the amygdala is central to handling the demands of complex social life in primates. In this paper, we synthesize extant anatomical and functional data from rodents, monkeys, and humans to describe the topography of three partially distinct large-scale brain networks anchored in the amygdala that each support unique functions for effectively managing social interactions and maintaining social relationships. These findings provide a powerful componential framework for parsing social behavior into partially distinct neural underpinnings that differ among healthy people and disintegrate or fail to develop in neuropsychiatric populations marked by social impairment, such as autism, antisocial personality disorder, and frontotemporal dementia.

Serotoninergic effects on judgments and social learning of trustworthiness

RATIONALE

Certain disorders, such as depression and anxiety, to which serotonin dysfunction is historically associated, are also associated with lower assessments of other people's trustworthiness. Serotonergic changes are known to alter cognitive responses to threatening stimuli. This effect may manifest socially as reduced apparent trustworthiness of others. Trustworthiness judgments can emerge from either direct observation or references provided by third parties.

OBJECTIVE

We assessed whether explicit judgments of trustworthiness and social influences on those judgments are altered by changes within serotonergic systems.

METHODS

We implemented a double-blind between-subject design where 20 healthy female volunteers received a single dose of the selective serotonin reuptake inhibitor (SSRI) citalopram (2 × 20 mg), while 20 control subjects (matched on age, intelligence, and years of education) received a placebo. Subjects performed a face-rating task assessing how trustworthy they found 153 unfamiliar others (targets). After each rating, the subjects were told how other subjects, on average, rated the same target. The subjects then performed 30 min of distractor tasks before, unexpectedly, being asked to rate all 153 faces again, in a random order.

RESULTS

Compared to subjects receiving a placebo, subjects receiving citalopram rated targets as less trustworthy. They also conformed more to opinions of others, when others rated targets to be even less trustworthy than subjects had initially indicated. The two effects were independent of negative effects of citalopram on subjective state.

CONCLUSIONS

This is evidence that serotonin systems can mediate explicit assessment and social learning of the trustworthiness of others.

Atrophy in distinct corticolimbic networks in frontotemporal dementia relates to social impairments measured using the Social Impairment Rating Scale

Patients with frontotemporal dementia (FTD) often exhibit prominent, early and progressive impairments in social behaviour. We developed the Social Impairment Rating Scale (SIRS), rated by a clinician after a structured interview, which grades the types and severity of social behavioural symptoms in seven domains. In 20 FTD patients, we used the SIRS to study the anatomic basis of social impairments. In support of hypotheses generated from a prior study of healthy adults, we found that the relative magnitude of brain atrophy in three partially dissociable corticolimbic networks anchored in the amygdala predicted the severity of distinct social impairments measured using the SIRS. Patients with the greatest atrophy in a mesolimbic, reward-related (affiliation) network exhibited the most severe socioemotional detachment, whereas patients with the greatest atrophy in an interoceptive, pain-related (aversion) network exhibited the most severe lack of social apprehension. Patients with the greatest atrophy in a perceptual network exhibited the most severe lack of awareness or understanding of others' social and emotional behaviour. Our findings underscore observations that FTD is associated with heterogeneous social symptoms that can be understood in a refined manner by measuring impairments in component processes subserved by dissociable neural networks. Furthermore, these findings support the validity of the SIRS as an instrument to measure the social symptoms of patients with FTD. Ultimately, we hope it will be useful as a longitudinal outcome measure in natural history studies and in clinical trials of putative interventions to improve social functioning.

Opioid receptor blockade and warmth-liking: effects on interpersonal trust and frontal asymmetry

The emotion 'warmth-liking' (WL) associated with feelings of affection and acceptance is regularly activated in social contexts. WL has been suggested to be more closely related to the consummatory phase of post-goal attainment positive affect than to pre-goal attainment positive affect/approach motivation and to be partly mediated by brain opioids. To validate these assumptions we employed film/imagery to induce either a neutral emotional state or WL in female participants after intake of either placebo or the opioid antagonist naltrexone. Dependent variables were emotion self-report, interpersonal trust (TRUST, i.e. a behavioral indicator of WL) and frontal asymmetry (i.e. an electroencephalogram (EEG) indicator of approach motivation/behavioral activation). We found that participants reported more WL in the placebo/WL group than in the placebo/neutral group and both naltrexone groups. In addition, TRUST increased in the WL group after placebo, but not after naltrexone, and this pattern was reversed in the neutral control groups. Consequently, opioid blockade suppressed or even reversed the effects of the WL induction on the levels of self-report and behavior, respectively. In addition, we observed reduced relative left-frontal asymmetry in the WL (vs neutral) group, consistent with reduced approach motivation. Overall, these results suggest opioidergic influences on WL and TRUST and reduced approach motivation/behavioral activation for the positive emotion WL.

Paranoid thinking, suspicion, and risk for aggression: a neurodevelopmental perspective

This article represents an effort to extend our understanding of paranoia or suspicion and its development by integrating findings across clinical, developmental, and neuroscience literatures. We first define "paranoia" or paranoid thought and examine its prevalence across typically and atypically developing individuals and theoretical perspectives regarding its development and maintenance. We then briefly summarize current ideas regarding the neural correlates of adaptive, appropriately trusting interpersonal perception, social cognition, and behavior across development. Our focus shifts subsequently to examining in normative and atypical developmental contexts the neural correlates of several component cognitive processes thought to contribute to paranoid thinking: (a) attention bias for threat, (b) jumping to conclusions biases, and (c) hostile intent attribution biases. Where possible, we also present data regarding independent links between these cognitive processes and aggressive behavior. By examining data regarding the behavioral and neural correlates of varied cognitive processes that are likely components of a paranoid thinking style, we hope to advance both theoretical and empirical research in this domain.

A neural signature of affiliative emotion in the human septohypothalamic area

Comparative studies have established that a number of structures within the rostromedial basal forebrain are critical for affiliative behaviors and social attachment. Lesion and neuroimaging studies concur with the importance of these regions for attachment and the experience of affiliation in humans as well. Yet it remains obscure whether the neural bases of affiliative experiences can be differentiated from the emotional valence with which they are inextricably associated at the experiential level. Here we show, using functional MRI, that kinship-related social scenarios evocative of affiliative emotion induce septal-preoptic-anterior hypothalamic activity that cannot be explained by positive or negative emotional valence alone. Our findings suggest that a phylogenetically conserved ensemble of basal forebrain structures, especially the septohypothalamic area, may play a key role in enabling human affiliative emotion. Our finding of a neural signature of human affiliative experience bears direct implications for the neurobiological mechanisms underpinning impaired affiliative experiences and behaviors in neuropsychiatric conditions.

Oxytocin in schizophrenia: a review of evidence for its therapeutic effects

BACKGROUND

The suggestion that the neurohormone oxytocin may have clinical application in the treatment of schizophrenia was first published in 1972. Since then, a considerable body of research on a variety of fronts--including several recent double-blind treatment trials-has buttressed these early reports, providing support for the assertion that the oxytocin system is a promising and novel therapeutic target for this devastating malady. Herein, we review the diverse, convergent lines of evidence supporting the therapeutic potential of oxytocin in psychotic illness.

METHODS

We performed a systematic review of preclinical and clinical literature pertaining to oxytocin's role in schizophrenia.

RESULTS

Multiple lines of evidence converge to support the antipsychotic potential of oxytocin. These include several animal models of schizophrenia, pharmacological studies examining the impact of antipsychotics on the oxytocin system, human trials in patients examining aspects of the oxytocin system, and several double-blind, placebo-controlled clinical treatment trials.

CONCLUSIONS

There exists considerable, convergent evidence that oxytocin has potential as a novel antipsychotic with a unique mechanism of action. Auspiciously, based on the few chronic trials to date, its safety profile and tolerability appear very good. That said, several critical clinical questions await investigation before widespread use is clinically warranted.

Race and reputation: perceived racial group trustworthiness influences the neural correlates of trust decisions

Decisions to trust people with whom we have no personal history can be based on their social reputation-a product of what we can observe about them (their appearance, social group membership, etc.)-and our own beliefs. The striatum and amygdala have been identified as regions of the brain involved in trust decisions and trustworthiness estimation, respectively. However, it is unknown whether social reputation based on group membership modulates the involvement of these regions during trust decisions. To investigate this, we examined blood-oxygenation-level-dependent (BOLD) activity while participants completed a series of single-shot trust game interactions with real partners of varying races. At the time of choice, baseline BOLD responses in the striatum correlated with individuals' trust bias-that is, the overall disparity in decisions to trust Black versus White partners. BOLD signal in the striatum was higher when deciding to trust partners from the race group that the individual participant considered less trustworthy overall. In contrast, activation of the amygdala showed greater BOLD responses to Black versus White partners that scaled with the amount invested. These results suggest that the amygdala may represent emotionally relevant social group information as a subset of the general detection function it serves, whereas the striatum is involved in representing race-based reputations that shape trust decisions.

Brain evolution and human neuropsychology: the inferential brain hypothesis

Collaboration between human neuropsychology and comparative neuroscience has generated invaluable contributions to our understanding of human brain evolution and function. Further cross-talk between these disciplines has the potential to continue to revolutionize these fields. Modern neuroimaging methods could be applied in a comparative context, yielding exciting new data with the potential of providing insight into brain evolution. Conversely, incorporating an evolutionary base into the theoretical perspectives from which we approach human neuropsychology could lead to novel hypotheses and testable predictions. In the spirit of these objectives, we present here a new theoretical proposal, the Inferential Brain Hypothesis, whereby the human brain is thought to be characterized by a shift from perceptual processing to inferential computation, particularly within the social realm. This shift is believed to be a driving force for the evolution of the large human cortex. (JINS, 2012, 18, 394-401).

The neural basis of following advice

Learning by following explicit advice is fundamental for human cultural evolution, yet the neurobiology of adaptive social learning is largely unknown. Here, we used simulations to analyze the adaptive value of social learning mechanisms, computational modeling of behavioral data to describe cognitive mechanisms involved in social learning, and model-based functional magnetic resonance imaging (fMRI) to identify the neurobiological basis of following advice. One-time advice received before learning had a sustained influence on people's learning processes. This was best explained by social learning mechanisms implementing a more positive evaluation of the outcomes from recommended options. Computer simulations showed that this “outcome-bonus” accumulates more rewards than an alternative mechanism implementing higher initial reward expectation for recommended options. fMRI results revealed a neural outcome-bonus signal in the septal area and the left caudate. This neural signal coded rewards in the absence of advice, and crucially, it signaled greater positive rewards for positive and negative feedback after recommended rather than after non-recommended choices. Hence, our results indicate that following advice is intrinsically rewarding. A positive correlation between the model's outcome-bonus parameter and amygdala activity after positive feedback directly relates the computational model to brain activity. These results advance the understanding of social learning by providing a neurobiological account for adaptive learning from advice.

Learning by following advice is fundamental for human cultural evolution. Yet it is largely unknown how the brain implements advice-taking in order to maximize rewards. Here, we used functional magnetic resonance imaging (fMRI) and behavioral experiments to study how people use one-off advice. We find that advice had a sustained effect on choices and modulated learning in two ways. First, participants initially assumed that the recommended option was most beneficial. Second, and more importantly, gains and losses obtained after following advice received an “outcome-bonus,” in which they were evaluated more positively than after not following advice. In other words, following advice was in general intrinsically rewarding. Computer simulations showed that the outcome-bonus is adaptive, because it benefits from good advice and limits the effect of bad advice. The fMRI analysis revealed a neural outcome-bonus signal in the septal area and left caudate head, structures previously implicated in trust and reward based learning. Participants with greater outcome-bonuses showed a greater gain-signal increase after following advice in the amygdala, a structure implicated in processing emotions and social information. In sum, these results suggest that decision makers adaptively combine advice and individual learning with a social learning mechanism in which advice modulates the neural reward response.