Increasing the role of belief information in moral judgments by stimulating the right temporoparietal junction

The neural structures of theory of mind are valence-sensitive: evidence from three tDCS studies

Several cortical structures are involved in theory of mind (ToM), including the dorsolateral prefrontal cortex (dlPFC), the ventromedial prefrontal cortex (vmPFC), and the right temporo- parietal junction (rTPJ). We investigated the role of these regions in mind reading with respect to the valence of mental states. Sixty-five healthy adult participants were recruited and received transcranial direct current stimulation (tDCS) (1.5 mA, 20 min) with one week interval in three separate studies. The stimulation conditions were anodal tDCS over the dlPFC coupled with cathodal tDCS over the vmPFC, reversed stimulation conditions, and sham in the first study, and anodal tDCS over the vmPFC, or dlPFC, and sham stimulation, with an extracranial return electrode in the second and third study. During stimulation, participants underwent the reading mind from eyes/voice tests (RMET or RMVT) in each stimulation condition. Anodal left dlPFC/cathodal right vmPFC stimulation increased the accuracy of negative mental state attributions, anodal rTPJ decreased the accuracy of negative and neutral mental state attributions, and decreased the reaction time of positive mental state attributions. Our results imply that the neural correlates of ToM are valence-sensitive.

Shared intentionality modulates interpersonal neural synchronization at the establishment of communication system

Whether and how shared intentionality (SI) influences the establishment of a novel interpersonal communication system is poorly understood. To investigate this issue, we designed a coordinating symbolic communication game (CSCG) and applied behavioral, functional near-infrared spectroscopy (fNIRS)-based hyperscanning, and hyper-transcranial alternating current stimulation (hyper-tACS) methods. Here we show that SI is a strong contributor to communicative accuracy. Moreover, SI, communicative accuracy, and interpersonal neural synchronization (INS) in the right superior temporal gyrus (rSTG) are higher when dyads successfully establish a novel communication system. Furthermore, the SI influences communicative accuracy by increasing INS. Additionally, using time series and long short-term memory neural network analyses, we find that the INS can predict communicative accuracy at the early formation stage of the communication system. Importantly, the INS partially mediates the relationship between the SI and the communicative accuracy only at the formation stage of the communication system. In contrast, when the communication system is established, SI and INS no longer contribute to communicative accuracy. Finally, the hyper-tACS experiment confirms that INS has a causal effect on communicative accuracy. These findings suggest a behavioral and neural mechanism, subserved by the SI and INS, that underlies the establishment of a novel interpersonal communication system.

Breakdown of intention-based outcome evaluation after transient right temporoparietal junction deactivation

People judge the nature of human behaviors based on underlying intentions and possible outcomes. Recent studies have demonstrated a causal role of the right temporoparietal junction (rTPJ) in modulating both intention and intention-based outcome evaluations during social judgments. However, these studies mainly used hypothetical scenarios with socially undesirable contexts (bad/neutral intentions and bad/neutral outcomes), leaving the role of rTPJ in judging good intentions and good outcomes unclear. In the current study, participants were instructed to make goodness judgments as a third party toward the monetary allocations from one proposer to another responder. Critically, in some cases, the initial allocation by the proposer could be reversed by the computer, yielding combinations of good/bad intentions (of the proposer) with good/bad outcomes (for the responder). Anodal (n = 20), cathodal (n = 21), and sham (n = 21) transcranial direct current stimulation (tDCS) over the rTPJ were randomly assigned to 62 subjects to further examine the effects of stimulation over the rTPJ in modulating intention-based outcome evaluation. Compared to the anodal and sham stimulations, cathodal tDCS over the rTPJ reduced the goodness ratings of good/bad outcomes when the intentions were good, whereas it showed no significant effect on outcome ratings under unknown and bad intentions. Our results provide the first evidence that deactivating the rTPJ modulates outcome evaluation in an intention-dependent fashion, mainly by reducing the goodness rating towards both good/bad outcomes when the intentions are good. Our findings argue for a causal role of the rTPJ in modulating intention-based social judgments and point to nuanced effects of rTPJ modulation.

Neuromodulation of the right temporoparietal junction alters amygdala functional connectivity to authority pressure

Past historical events and experimental research have shown that complying with orders from an authority has a strong impact on harming/destructive behavior, but no one has ever looked into the potential intervention and its neural underpinning to reveal the toll of coercion. We used a paradigm of virtual obedience to authority, in which an experimenter ordered a volunteer to press a handheld button to initiate actions that carried different consequences, including harming or helping others. In this study, we scanned the brain with functional neuroimaging and applied transcranial direct current stimulation (tDCS) to modulate the activation of the right temporoparietal junction (rTPJ) in healthy volunteers in a single-blinded, sham-controlled, crossover trial with anodal, cathodal, and sham stimulation. We observed that cathodal stimulation, compared to anodal and sham stimulation, significantly reduced reaction times (RTs) to initiating harming actions. The effect of tDCS on the rTPJ, orbitofrontal cortex, and anterior cingulate cortex had opposite directions depending on coercive harming or helping actions. Cathodal tDCS-induced changes in the strength of the functional connectivity between the rTPJ and amygdala predicted the effect of cathodal tDCS on harming RTs. The findings provide evidence supporting the rTPJ having a role in coercion-induced changes in the sense of agency. Neuromodulation with tDCS might help in unveiling the power of authority and assisting in the emergence of prosocial behavior, thus shedding light on coping strategies against coercion beyond merely examining its effects.

Culture, theory-of-mind, and morality: How independent and interdependent minds make moral judgments

Although the investigation of the neural mechanisms of morality has increased in recent years, the neural underpinnings of cultural variations in judgments of morality is understudied. In this paper, we propose that the well-established cultural differences in two cognitive processes, consideration of mental state and causal attribution, would lead to differences in moral judgment. Specifically, North Americans rely heavily on the mental state of a protagonist and dispositional attributions, whereas East Asians focus more on situational attributions and place less emphasis on the mental state of a protagonist. These differences would be accounted for by activity in brain regions implicated in thinking about others' minds, or theory-of-mind (ToM), which would underlie the cultural shaping of moral judgment. This proposed cultural neuroscience approach may broaden the scope of morality research, better predict moral behavior, and reduce disparities in diverse groups' moral judgment.

You feel me? A randomized trial of tDCS on pain empathy

Pain empathy has a number of social benefits, but can be problematic in those who feel the pain of others too much. The current study examined the use of transcranial direct current stimulation (tDCS) as a modifier of pain empathy with the expectation that cathodal stimulation would decrease pain empathy. Anxiety and general empathy were controlled for, given past work demonstrating their impact on pain empathy. Participants were randomized to either active (cathodal; n = 55) or sham tDCS (n = 55) at 2 mA for 20 min while watching videos of painful events and completing a pain empathy simulation questionnaire. Bayesian linear regression analysis indicated no evidence that tDCS condition affected pain empathy. However, there was strong evidence in favor of a positive relationship between anxiety and pain empathy, and extreme evidence between general empathy and pain empathy. The current study examined a montage over the temporoparietal junction though future work should also investigate other areas related to pain empathy such as the anterior cingulate cortex. Results provide evidence of the need for stronger methodological considerations with regard to tDCS including larger sample sizes. Further, the connection between anxiety and pain empathy demonstrates the need for treatments to not only target classic anxiety symptoms, but other factors than may worsen daily functioning.

Wired to Punish? Electroencephalographic Study of the Resting-state Neuronal Oscillations Underlying Third-party Punishment

For over a decade, neuroimaging and brain stimulation studies have investigated neural mechanisms of third-party punishment, a key instrument for social norms enforcement. However, the neural dynamics underlying these mechanisms are still unclear. Previous electroencephalographic studies on third-party punishment have shown that inter-brain connectivity is linked to punishment behavior. However, no clear evidence was provided regarding whether the effect of inter-brain connectivity on third-party punishment is mediated by local neuronal states. In this study, we further investigate whether resting-state neuronal activity in the alpha frequency range can predict individual differences in third-party punishment. More specifically, we show that the global resting-state connectivity between the right dorsolateral prefrontal and right temporo-parietal regions is negatively correlated with the level of third-party punishment. Additionally, individuals with stronger local resting-state long-range temporal correlations in the right temporo-parietal cortices demonstrated a lower level of third-party punishment. Thus, our results further support the idea that global and local neuronal dynamics can contribute to individual differences in third-party punishment.

Effects of anodal multichannel transcranial direct current stimulation (tDCS) on social-cognitive performance in healthy subjects: A randomized sham-controlled crossover pilot study

Recent studies suggest that temporoparietal junction (TPJ) modulation can influence attention and social cognition performance. Nevertheless, no studies have used multichannel transcranial direct current stimulation (tDCS) over bilateral TPJ to estimate the effects on these neuropsychological functions. The project STIPED is using optimized multichannel stimulation as an innovative treatment approach for chronic pediatric neurodevelopmental disorders, namely in children/adolescents with Autism Spectrum Disorder (ASD). In this pilot study, we aim to explore whether anodal multichannel tDCS coupled with a Joint Attention Task (JAT) influences social-cognitive task performance relative to sham stimulation, both in an Emotion Recognition Task (ERT) and in a Mooney Faces Detection Task (MFDT), as well as to evaluate this technique's safety and tolerability. Twenty healthy adults were enrolled in a randomized, single-blinded, sham-controlled, crossover study. During two sessions, participants completed the ERT and the MFDT before and after 20min of sham or anodal tDCS over bilateral TPJ. No significant differences on performance accuracy and reaction time were found between stimulation conditions for all tasks, including the JAT. A significant main time effect for overall accuracy and reaction time was found for the MFDT. Itching was the most common side effect and stimulation conditions detection was at chance level. Results suggest that multichannel tDCS over bilateral TPJ does not affect performance of low-level emotional recognition tasks in healthy adults. Although preliminary safety and tolerability are demonstrated, further studies over longer periods will be pursued to investigate the clinical efficacy in children/adolescents with ASD, where social cognition impairments are preponderant.

The tDCS effect on Prosocial Behavior: A Meta-Analytic Review

Previous studies have shown that transcranial direct current stimulation (tDCS) could potentially promote prosocial behaviors. However, results from randomized controlled trials are inconsistent. The current meta-analysis aimed to assess the effects of anodal and cathodal tDCS using single-session protocols on prosocial behaviors in healthy young adults and explore potential moderators of these effects. The results showed that compared with sham stimulation, anodal (excitatory) stimulation significantly increased (g = 0.27, 95% CI [0.11, 0.43], Z = 3.30, P = 0.001) and cathodal (inhibitory) stimulation significantly decreased prosocial behaviors (g = −0.19, 95% CI [−0.39, −0.01], Z = −1.95, P = 0.051) using a multilevel meta-analytic model. These effects were not significantly modulated by stimulation parameters (e.g. duration, intensity and site) and types of prosocial behavior. The risk of publication bias for the included effects was minimal, and no selective reporting (e.g. P-hacking) was found in the P-curve analysis. This meta-analysis showed that both anodal and cathodal tDCS have small but significant effects on prosocial behaviors. The current study provides evidence that prosocial behaviors are linked to the activity of the ‘social brain’. Future studies are encouraged to further explore whether tDCS could effectively treat social dysfunctions in psychiatry disorders.

SLC6A4 polymorphisms modulate the efficacy of a tryptophan-enriched diet on age-related depression and social cognition

BACKGROUND & AIMS

In a placebo controlled study we sought to determine if a four-weeks tryptophan-enriched diet is able to improve age-related depression or social cognitive impairment, depending on polymorphisms located in the promoter region of Solute Carrier Family 6 Member 4 (SLC6A4), also known as serotonin transporter (SERT1) gene.

METHODS

91 young volunteers (age: 21 ± 2 yrs) and 127 above 50 years old (58 ± 6 yrs) healthy volunteers completed the study. Participants from the placebo and tryptophan group followed the same protocol. Before starting the study blood samples, to measure serotonin-transporter-linked polymorphic region (5-HTTLPR) and rs25531 polymorphisms, were collected. In addition, before and after completing the study urine samples (to measure 5-hydroxyindolacetic acid (5-HIAA) were taken, while psychological questionnaires (to assess depression and social cognition levels), and a one week dietary record (to calculate the tryptophan (TRP) intake) were assessed.

RESULTS

The triallelic approach of SLC6A4 showed that in S'S´ subjects there was a positive correlation between TRP intake and 5-HIAA levels. Age of participants, SLC6A4 genotype, and experimental condition were important factors contributing to the outcome of depression and social cognition.

CONCLUSIONS

5-HTTLPR and rs25531 polymorphisms play a key role in the response to the TRP- based nutritional intervention, improving only age-related depressive symptoms and empathy in S'S´ subjects who have a higher risk to show signs of depression during their lifetime.

Modulating the activity of right temporo-parietal junction by anodal tDCS enhances the agent's repayment in hold-up game

Hold-up problem is very common in non-contractible relation-specific investment transactions. And this problem can affect by trust, cooperation and altruism behavior of human beings. Recent neuroscience researches had explored a network of right temporo-parietal junction (rTPJ) involved in human cooperation and altruism behavior. The purpose of this study is to modulate the activation of rTPJ through transcranial direct current stimulation (tDCS), and to study the influence of rTPJ on investment and offer behavior in hold-up game. The results of our study showed that the anodal stimulation significantly increased participants' offer compared with the cathodal and sham stimulation. A possible explanation is that changes in rTPJ activity induced by anodal stimulation improve the accuracy of agents' mental reasoning and promote cooperation by influencing agents' offer behavior.

Morality in autism spectrum disorder: A systematic review

Moral reasoning and decision making help guide behavior and facilitate interpersonal relationships. Accounts of morality that position commonsense psychology as the foundation of moral development, (i.e., rationalist theories) have dominated research in morality in autism spectrum disorder (ASD). Given the well-documented differences in commonsense psychology among autistic individuals, researchers have investigated whether the development and execution of moral judgement and reasoning differs in this population compared with neurotypical individuals. In light of the diverse findings of investigations of moral development and reasoning in ASD, a summation and critical evaluation of the literature could help make sense of what is known about this important social-cognitive skill in ASD. To that end, we conducted a systematic review of the literature investigating moral decision making among autistic children and adults. Our search identified 29 studies. In this review, we synthesize the research in the area and provide suggestions for future research. Such research could include the application of an alternative theoretical framework to studying morality in autism spectrum disorder that does not assume a deficits-based perspective.

Neural correlations of the influence of self-relevance on moral decision-making involving a trade-off between harm and reward

Although economists have suggested that humans generally prioritize maximizing their own self-interest rather than others' when distributing rewards, recent psychological studies have shown that people are hyperaltruistic when allocating physical harm to themselves and others during moral decision-making. However, little is known about how the neurocognitive mechanisms underlying self-relevance modulate this behavioral tendency under different degrees of physical harm. This study adopted a moral decision-making task to investigate behavioral and neural processes during moral decision-making involving different levels of self-relevance and physical harm. Event-related potentials were measured while participants made trade-offs of different monetary gains for themselves against painful electric shocks experienced by the receivers (self, friend, or stranger). These results suggest that early anterior N1, indexing fast and automatic moral intuitional process, decreased during the strong conflict trade-off decisions involving strong painful electric shocks and much monetary gains. Lower self-relevance enhanced the aversive experience and increased the mental cost of resolving moral conflict, reflected by a larger P260-LPP (300-450 ms) effect during weaker conflict decisions toward strangers than themselves and friends. However, this effect was weaker during strong conflict decisions. When making decisions about whether to shock others to gain money for themselves, participants were hyperaltruistic, foregoing greater self-interest to restrain harm directed toward strangers than themselves or friends. These findings shed light on the neural basis of the tension between egoistic and altruistic tendencies during moral decision-making integrating benefits and harms.

Group membership dictates the neural correlates of social optimism biases

Optimism bias, i.e. expecting the future to hold more desirable than undesirable outcomes, also extends to people that we like or admire. However, it remains unknown how the brain generates this social optimism bias. In this study, respondents estimated the likelihood of future desirable and undesirable outcomes for an in-group and three out-groups: warm-incompetent, cold-competent, and cold-incompetent. We found a strong social optimism bias for the in-group and the warm out-group and an inverted pattern for the cold-incompetent out-group. For all groups, scores of social optimism bias correlated with the brain activity in structures that respondents differentially engaged depending on the target social group. In line with our hypotheses, evaluating the in-group recruited the ventromedial prefrontal cortex and the precuneus/posterior cingulate cortex, whereas evaluating the warm out-group engaged the posterior insula, mid cingulate cortex, and somatosensory cortices. These findings suggest different underlying cognitive mechanisms of social optimism bias for these groups, despite similar behavioural patterns. Thinking about the cold out-groups recruited the right anterior temporal lobe, and temporoparietal junction. Evaluating the cold-incompetent out-group additionally recruited the anterior insula, inferior frontal cortex and dorsomedial frontal cortex. We discuss these neuroimaging findings with respect to their putative cognitive functions.

Anodal tDCS Over the Right Temporoparietal Junction Lowers Overbidding in Contests

Overbidding, which means bidding over the Nash equilibrium, is commonly observed in competitive social interactions, such as a contest or auction. Recent neuroscience studies show that the right temporoparietal junction (rTPJ) is related to overbidding and associated with inferring the intentions of others during competitive interactions. The present study investigates the neural underpinnings of overbidding and how the rTPJ impacts bidding behavior by using tDCS to modulate the activation of the rTPJ. Participants completed a two-person proportional prize contest, in which overbidding was frequently observed and each participant's share of the prize was equal to the individual's expenditure divided by the aggregated expenditure. We observed a significant tDCS effect, i.e., participants' average expenditure and overbidding rate were significantly reduced in the anodal stimulation compared with the cathodal and sham stimulation. Possible explanations include that enhanced activity in the rTPJ via the anodal stimulation increased the accuracy of a participant's inference of the strategies of others, or a participant's concern for others, and thus helped the participant bid optimally. Our findings provide evidence supporting that the activation of the rTPJ in contests affects overbidding and bidding strategy, and further confirm that the rTPJ is involved in the inference of mental states in a competition context.

Cortical morphometry of the five-factor model of personality: findings from the Human Connectome Project full sample

This study is a replication of an existing large study (N = 507) on the surface-based morphometric correlates of five-factor model (FFM) personality traits. The same methods were used as the original study in another large sample drawn from the same population (N = 597) with results then being aggregated from both samples (N = 1104), providing the largest investigation into the neuroanatomical correlates of FFM personality traits to date. Clusters of association between brain morphometry and each FFM trait are reported. For neuroticism, agreeableness, openness and conscientiousness clusters of association were found in the dorsolateral prefrontal cortex for at least one morphometric index. Morphometry in various other regions was also associated with each personality trait. While some regions found in the original study were confirmed in the replication and full samples, others were not, highlighting the importance of replicating even high-quality, well-powered studies. Effect sizes were very similar in the replication and whole samples as those found in the original study. As a whole, the current results provide the strongest evidence to date on the neuroanatomical correlates of personality and highlights challenges in using this approach to understanding the neural correlates of personality.

When morality opposes the law: An fMRI investigation into punishment judgments for crimes with good intentions

In judicial practice, morally right but legally wrong instances usually pose significant challenges for legal decision makers. To examine the cognitive and neural foundations of legal judgments in criminal cases involving apparent moral conflicts, we scanned 30 female participants during punishment judgments for crimes committed with good intentions. The behavioral results confirmed that moral acceptability was significantly correlated with the punishment ratings only in the good-intentioned crimes. The fMRI data mainly revealed that the right temporoparietal junction (rTPJ) plays special roles in processing criminal offenders' state of mind and that the right dorsal lateral prefrontal cortex (rDLPFC) plays roles in resolving moral conflicts involved in legal judgments. Specifically, we found that compared to the bad-intentioned scenarios, the good-intentioned scenarios evoked greater activities during the postreading stage in the brain area of the rTPJ and that a signal increase in the rTPJ was associated with more lenient penalty judgments in the good-intentioned scenarios. Furthermore, reading crime scenarios with good intentions elicited stronger activation in the rdlPFC, which showed enhanced functional connectivity with the medial prefrontal cortex (mPFC). Overall, our study sheds some light on the neurocognitive underpinnings of legal judgments in special criminal cases and enhances our understanding of the relationship between legal and moral judgments.

A double-blind HD-tDCS/EEG study examining right temporoparietal junction involvement in facial emotion processing

Prior studies have demonstrated that aspects of social cognition can be modulated via temporoparietal junction (TPJ) transcranial direct current stimulation (tDCS). However, this technique lacks focality and electrophysiological effects or correlates are rarely examined. The present study investigated whether anodal and/or cathodal high-definition tDCS (HD-tDCS) would influence facial emotion processing performance relative to sham stimulation, and whether task performance changes were related to neurophysiological changes. Participants completed a facial emotion attribution tasks before and after rTPJ HD-tDCS, with event-related potentials (ERP) recorded during task performance. Anodal rTPJ HD-tDCS improved facial emotion processing performance for static depictions of fear (but not surprise). Stimulation condition influenced P300 latency, and also influenced the relationship between behavioural and electrophysiological (ERP) outcomes in several circumstances, findings which both support and challenge anodal-excitation/cathodal-inhibition accounts of tDCS effects. Results suggest that rTPJ anodal HD-tDCS can influence facial emotion recognition (i.e., affective mentalizing), and elucidate the nature and distribution of underlying neurophysiological processes. Stimulation effects, however, might depend on the intensity and salience/valence (negativity/threat) of the emotion, and these behavioural effects may not relate directly or simply to the ERPs assessed here.

Moral Judgment: An Overlooked Deficient Domain in Multiple Sclerosis?

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disease of the central nervous system through which patients can suffer from sensory, motor, cerebellar, emotional, and cognitive symptoms. Although cognitive and behavioral dysfunctions are frequently encountered in MS patients, they have previously received little attention. Among the most frequently impaired cognitive domains are attention, information processing speed, and working memory, which have been extensively addressed in this population. However, less emphasis has been placed on other domains like moral judgment. The latter is a complex cognitive sphere that implies the individuals’ ability to judge others’ actions and relies on numerous affective and cognitive processes. Moral cognition is crucial for healthy and adequate interpersonal relationships, and its alteration might have drastic impacts on patients’ quality of life. This work aims to analyze the studies that have addressed moral cognition in MS. Only three works have previously addressed moral judgement in this clinical population compared to healthy controls, and none included neuroimaging or physiological measures. Although scarce, the available data suggest a complex pattern of moral judgments that deviate from normal response. This finding was accompanied by socio-emotional and cognitive deficits. Only preliminary data are available on moral cognition in MS, and its neurobiological foundations are still needing to be explored. Future studies would benefit from combining moral cognitive measures with comprehensive neuropsychological batteries and neuroimaging/neurophysiological modalities (e.g., functional magnetic resonance imaging, tractography, evoked potentials, electroencephalography) aiming to decipher the neural underpinning of moral judgement deficits and subsequently conceive potential interventions in MS patients.

Transcranial Direct Current Stimulation of the Right Lateral Prefrontal Cortex Changes a priori Normative Beliefs in Voluntary Cooperation

A priori normative beliefs, the precondition of social norm compliance that reflects culture and values, are considered unique to human social behavior. Previous studies related to the ultimatum game revealed that right lateral prefrontal cortex (rLPFC) has no stimulation effects on normative beliefs. However, no research has focused on the effects of a priori belief on the rLPFC in voluntary cooperation attached to the public good (PG) game. In this study, we used a linear asymmetric PG to confirm the influence of the rLPFC on a priori normative beliefs without threats of external punishment through transcranial direct current stimulation (tDCS). Participants engaged via computer terminals in groups of four (i.e., two high-endowment players with 35G$ and two low-endowment players with 23G$). They were anonymous and had no communication during the entire process. They were randomly assigned to receive 15 min of either anodal, cathodal, or sham stimulation and then asked to answer questions concerning a priori normative beliefs (norm.belief and pg.belief). Results suggested that anodal/cathodal tDCS significantly (P < 0.001) shifted the participants' a priori normative beliefs in opposite directions compared to the shift in the sham group. In addition, different identities exhibited varying degrees of change (28.80-54.43%). These outcomes provide neural evidence of the rLPFC mechanism's effect on the normative beliefs in voluntary cooperation based on the PG framework.

tDCS Over DLPFC Leads to Less Utilitarian Response in Moral-Personal Judgment

The profound nature of moral judgment has been discussed and debated for centuries. When facing the trade-off between pursuing moral rights and seeking better consequences, most people make different moral choices between two kinds of dilemmas. Such differences were explained by the dual-process theory involving an automatic emotional response and a controlled application of utilitarian decision-rules. In neurocognitive studies, the bilateral dorsolateral prefrontal cortex (DLPFC) has been demonstrated to play an important role in cognitive “rational” control processes in moral dilemmas. However, the profile of results across studies is not entirely consistent. Although one transcranial magnetic stimulation (TMS) study revealed that disrupting the right DLPFC led to less utilitarian responses, other TMS studies indicated that inhibition of the right DLPFC led to more utilitarian choices. Moreover, the right temporoparietal junction (TPJ) is essential for its function of integrating belief and intention in moral judgment, which is related to the emotional process according to the dual-process theory. Relatively few studies have reported the causal relationship between TPJ and participants' moral responses, especially in moral dilemmas. In the present study, we aimed to demonstrate a direct link between the neural and behavioral results by application of transcranial direct current stimulation (tDCS) in the bilateral DLPFC or TPJ of our participants. We observed that activating the right DLPFC as well as inhibiting the left DLPFC led to less utilitarian judgments, especially in moral-personal conditions, indicating that the right DLPFC plays an essential role, not only through its function of moral reasoning but also through its information integrating process in moral judgments. It was also revealed that altering the excitability of the bilateral TPJ using tDCS negligibly altered the moral response in non-moral, moral-impersonal and moral-personal dilemmas, indicating that bilateral TPJ may have little influence over moral judgments in moral dilemmas.

Transcranial Direct Current Stimulation of the Medial Prefrontal Cortex Affects Judgments of Moral Violations

Previous studies show that neural activities in the medial prefrontal cortex (mPFC) are correlated with moral processing during picture viewing tasks. In this study, we applied transcranial direct current stimulation (tDCS) to determine whether this non-invasive brain stimulation technique could modulate the evaluation of moral violations. Sixty-four subjects were randomly recruited, separated into different groups and tested with 42 pairs of pictures depicting moral violations. Each subject was required to rate the pictures two separate times, i.e., before and after tDCS intervention. We found that anodal tDCS (atDCS) increases cortical excitability over the mPFC (between the Fpz and Fp1 positions) as well as the sense of morality and emotional arousal of the subjects. In conclusion, this study indicated that the mPFC plays an important role in moral judgments while modulating ratings of moral violations under tDCS intervention conditions.

The stimulated social brain: effects of transcranial direct current stimulation on social cognition

Transcranial direct current stimulation (tDCS) is an increasingly popular noninvasive neuromodulatory tool in the fields of cognitive and clinical neuroscience and psychiatry. It is an inexpensive, painless, and safe brain-stimulation technique that has proven to be effective in modulating cognitive and sensory-perceptual functioning in healthy individuals and clinical populations. Importantly, recent findings have shown that tDCS may also be an effective and promising tool for probing the neural mechanisms of social cognition. In this review, we present the state-of-the-art of the field of tDCS research in social cognition. By doing so, we aim to gather knowledge of the potential of tDCS to modulate social functioning and social decision making in healthy humans, and to inspire future research investigations.

Electric stimulation of the right temporo-parietal junction induces a task-specific effect in deceptive behaviors

How the brain generates a lie is an important and unsolved issue in neuroscience. Previous studies indicated that mentalizing, the ability to understand and manipulate the mental states of others, plays a critical role in successful deception. Accordingly, recent neuroimaging studies reported deception-related activity in the right temporo-parietal junction (rTPJ), a brain region closely related to the mentalizing ability. Detailed functions of rTPJ in deception, however, remain unclear. In the present study, we investigated a causal relationship between rTPJ and deception using transcranial direct-current stimulation (tDCS). Subjects received anodal tDCS to their rTPJ or V1 (control) and then performed three tasks in which they aimed to deceive another participant to get monetary rewards. In one of the three tasks, we found a significant decrease in a rate of successful deception when rTPJ was stimulated, indicating that neural enhancement of rTPJ caused poorer (not better) deceptive performances. Our results suggest that, in some tasks involving selfish (money-motivated) lying, neural processing in rTPJ does not contribute to successful deception through the metalizing ability. Rather, it would be related to the self-monitoring of morally-unacceptable behaviors (lying). The neural enhancement of rTPJ therefore increased the psychological resistance to lying, resulting in poorer deceptive performances.

The behavioral and neural basis of empathic blame

Mature moral judgments rely both on a perpetrator’s intent to cause harm, and also on the actual harm caused–even when unintended. Much prior research asks how intent information is represented neurally, but little asks how even unintended harms influence judgment. We interrogate the psychological and neural basis of this process, focusing especially on the role of empathy for the victim of a harmful act. Using fMRI, we found that the ‘empathy for pain’ network was involved in encoding harmful outcomes and integrating harmfulness information for different types of moral judgments, and individual differences in the extent to which this network was active during encoding and integration of harmfulness information determined severity of moral judgments. Additionally, activity in the network was down-regulated for acceptability, but not blame, judgments for accidental harm condition, suggesting that these two types of moral evaluations are neurobiologically dissociable. These results support a model of “empathic blame”, whereby the perceived suffering of a victim colors moral judgment of an accidental harmdoer.

Neuroanatomical correlates of forgiving unintentional harms

Mature moral judgments rely on the consideration of a perpetrator’s mental state as well as harmfulness of the outcomes produced. Prior work has focused primarily on the functional correlates of how intent information is neurally represented for moral judgments, but few studies have investigated whether individual differences in neuroanatomy can also explain variation in moral judgments. In the current study, we conducted voxel-based morphometry analyses to address this question. We found that local grey matter volume in the left anterior superior temporal sulcus, a region in the functionally defined theory of mind or mentalizing network, was associated with the degree to which participants relied on information about innocent intentions to forgive accidental harms. Our findings provide further support for the key role of mentalizing in the forgiveness of accidental harms and contribute preliminary evidence for the neuroanatomical basis of individual differences in moral judgments.

Moral Enhancement Using Non-invasive Brain Stimulation

Biomedical enhancement refers to the use of biomedical interventions to improve capacities beyond normal, rather than to treat deficiencies due to diseases. Enhancement can target physical or cognitive capacities, but also complex human behaviors such as morality. However, the complexity of normal moral behavior makes it unlikely that morality is a single capacity that can be deficient or enhanced. Instead, our central hypothesis will be that moral behavior results from multiple, interacting cognitive-affective networks in the brain. First, we will test this hypothesis by reviewing evidence for modulation of moral behavior using non-invasive brain stimulation. Next, we will discuss how this evidence affects ethical issues related to the use of moral enhancement. We end with the conclusion that while brain stimulation has the potential to alter moral behavior, such alteration is unlikely to improve moral behavior in all situations, and may even lead to less morally desirable behavior in some instances.

Activation of the DLPFC Reveals an Asymmetric Effect in Risky Decision Making: Evidence from a tDCS Study

The phenomenon of loss aversion (the tendency for losses to have a greater impact than comparable gains) has long been observed in daily life. Neurocognitive studies and brain imaging studies have shed light on the correlation between the phenomenon of loss aversion and the brain region of the prefrontal cortex. Recent brain stimulation studies using bilateral transcranial magnetic stimulation or transcranial direct current stimulation (tDCS) have obtained various results showing the causal relationship between brain regions and decision making. With the goal of studying whether unilateral stimulation can change participants’ risky decision making in the frames of gains and losses, we applied different polarities of tDCS over the regions of the right or left prefrontal cortex. We also designed a risk measurement table (Multiple Price List) to reflect the participants’ attitudes toward risky decision making via the crossover point including the frames of gains and losses. The results of our experiment indicated that the participants tended to be more risk averse in the gain frame after receiving left anodal tDCS and more risk seeking in the loss frame after receiving right cathodal tDCS, which was consistent with the hypothesis that the process of risky decision making was correlated with the interaction of multiple systems in the brain. Our conclusion revealed an asymmetric effect of right/left DLPFC when the participants faced gains and losses, which partially provided the neural evidence and a feasible paradigm to help better understand risky decision making and loss aversion. The current study can not only expand the traditional understanding of the behavioral preferences of humans in economics but also accommodate empirical observations of behavioral economists on the preferences of humans.

Activation of the prefrontal cortex by unilateral transcranial direct current stimulation leads to an asymmetrical effect on risk preference in frames of gain and loss

Previous brain imaging and brain stimulation studies have suggested that the dorsolateral prefrontal cortex may be critical in regulating risk-taking behavior, although its specific causal effect on people's risk preference remains controversial. This paper studied the independent modulation of the activity of the right and left dorsolateral prefrontal cortex using various configurations of transcranial direct current stimulation. We designed a risk-measurement table and adopted a within-subject design to compare the same participant's risk preference before and after unilateral stimulation when presented with different frames of gain and loss. The results confirmed a hemispheric asymmetry and indicated that the right dorsolateral prefrontal cortex has an asymmetric effect on risk preference regarding frames of gain and loss. Enhancing the activity of the right dorsolateral prefrontal cortex significantly decreased the participants' degree of risk aversion in the gain frame, whereas it increased the participants' degree of risk aversion in the loss frame. Our findings provide important information regarding the impact of transcranial direct current stimulation on the risk preference of healthy participants. The effects observed in our experiment compared with those of previous studies provide further evidence of the effects of hemispheric and frame-dependent asymmetry. These findings may be helpful in understanding the neural basis of risk preference in humans, especially when faced with decisions involving possible gain or loss relative to the status quo.

Cathodal Transcranial Direct Current Stimulation on the Right Temporo-Parietal Junction Modulates the Use of Mitigating Circumstances during Moral Judgments

Recently, a few transcranial magnetic stimulation or transcranial direct current stimulation (tDCS) studies have shown that the right temporo-parietal junction (rTPJ) plays a causal role in moral reasoning especially in cases of accidental harms or attempted harms. The profile of results across studies is, however, not entirely consistent: sometimes the stimulation affects predominantly attempted harms while sometimes the stimulation affects predominantly accidental harms. We argue that such discrepancy could reflect different functional contributions of the rTPJ in moral judgments and that the chosen design parameters or stimulation method may differentially bring to light one or the other functional role of the rTPJ. In the current study, we found that tDCS specifically affected accidental harms but not attempted harms. Low cathodal stimulation of the rTPJ led to a marginally significant increase in the severity of judgments of accidental harms (Experiment 1) while higher cathodal current density led to a highly significant decrease in the severity of judgments of accidental harms (Experiment 2). Our pattern of results in the context of our experimental design can best be explained by a causal role of the rTPJ in processing the mitigating circumstances which reduce a protagonist's moral responsibility. We discuss these results in relation to the idea that the rTPJ may play multiple roles in moral cognition and in relation to methodological aspects related to the use of tDCS.

Using tDCS to Explore the Role of the Right Temporo-Parietal Junction in Theory of Mind and Cognitive Empathy

The right temporo-parietal junction (rTPJ) is thought to be closely related to theory of mind (ToM) and cognitive empathy. In the present study, we investigated whether these socio-cognitive abilities could be modulated with non-invasive transcranial direct current stimulation (tDCS) of the rTPJ. Participants received anodal (excitatory), cathodal (inhibitory), or sham stimulation before performing a social cognitive task which included inferring other’s intention (the ToM condition) and inferring other’s emotion (the cognitive empathy condition). Our results showed that the accuracy of both ToM and cognitive empathy decreased after receiving the cathodal stimulation, suggesting that altering the cortical excitability in the rTPJ could influence human’s socio-cognitive abilities. The results of this study emphasize the critical role of the rTPJ in ToM and cognitive empathy and demonstrate that these socio-cognitive abilities could be modulated by the tDCS.

Modulation of Neural Activity in the Temporoparietal Junction with Transcranial Direct Current Stimulation Changes the Role of Beliefs in Moral Judgment

Judgments about whether an action is morally right or wrong typically depend on our capacity to infer the actor’s beliefs and the outcomes of the action. Prior neuroimaging studies have found that mental state (e.g., beliefs, intentions) attribution for moral judgment involves a complex neural network that includes the temporoparietal junction (TPJ). However, neuroimaging studies cannot demonstrate a direct causal relationship between the activity of this brain region and mental state attribution for moral judgment. In the current study, we used transcranial direct current stimulation (tDCS) to transiently alter neural activity in the TPJ. The participants were randomly assigned to one of three stimulation treatments (right anodal/left cathodal tDCS, left anodal/right cathodal tDCS, or sham stimulation). Each participant was required to complete two similar tasks of moral judgment before receiving tDCS and after receiving tDCS. We studied whether tDCS to the TPJ altered mental state attribution for moral judgment. The results indicated that restraining the activity of the right temporoparietal junction (RTPJ) or the left the temporoparietal junction (LTPJ) decreased the role of beliefs in moral judgments and led to an increase in the dependance of the participants’ moral judgments on the action’s consequences. We also found that the participants exhibited reduced reaction times both in the cases of intentional harms and attempted harms after receiving right cathodal/left anodal tDCS to the TPJ. These findings inform and extend the current neural models of moral judgment and moral development in typically developing people and in individuals with neurodevelopmental disorders such as autism.