Neuro-computational mechanisms and individual biases in action-outcome learning under moral conflict.

Learning to predict action outcomes in morally conflicting situations is essential for social decision-making but poorly understood. Here we tested which forms of Reinforcement Learning Theory capture how participants learn to choose between self-money and other-shocks, and how they adapt to changes in contingencies. We find choices were better described by a reinforcement learning model based on the current value of separately expected outcomes than by one based on the combined historical values of past outcomes. Participants track expected values of self-money and other-shocks separately, with the substantial individual difference in preference reflected in a valuation parameter balancing their relative weight. This valuation parameter also predicted choices in an independent costly helping task. The expectations of self-money and other-shocks were biased toward the favored outcome but fMRI revealed this bias to be reflected in the ventromedial prefrontal cortex while the pain-observation network represented pain prediction errors independently of individual preferences.

How culturally unique are pandemic effects? Evaluating cultural similarities and differences in effects of age, biological sex, and political beliefs on COVID impacts.

Despite being bio-epidemiological phenomena, the causes and effects of pandemics are culturally influenced in ways that go beyond national boundaries. However, they are often studied in isolated pockets, and this fact makes it difficult to parse the unique influence of specific cultural psychologies. To help fill in this gap, the present study applies existing cultural theories via linear mixed modeling to test the influence of unique cultural factors in a multi-national sample (that moves beyond Western nations) on the effects of age, biological sex, and political beliefs on pandemic outcomes that include adverse financial impacts, adverse resource impacts, adverse psychological impacts, and the health impacts of COVID. Our study spanned 19 nations (participant N = 14,133) and involved translations into 9 languages. Linear mixed models revealed similarities across cultures, with both young persons and women reporting worse outcomes from COVID across the multi-national sample. However, these effects were generally qualified by culture-specific variance, and overall more evidence emerged for effects unique to each culture than effects similar across cultures. Follow-up analyses suggested this cultural variability was consistent with models of pre-existing inequalities and socioecological stressors exacerbating the effects of the pandemic. Collectively, this evidence highlights the importance of developing culturally flexible models for understanding the cross-cultural nature of pandemic psychology beyond typical WEIRD approaches.

Large Gatherings? No, Thank You. Devaluation of Crowded Social Scenes During the COVID-19 Pandemic.

In most European countries, the first wave of the COVID-19 pandemic (spring 2020) led to the imposition of physical distancing rules, resulting in a drastic and sudden reduction of real-life social interactions. Even people not directly affected by the virus itself were impacted in their physical and/or mental health, as well as in their financial security, by governmental lockdown measures. We investigated whether the combination of these events had changed people's appraisal of social scenes by testing 241 participants recruited mainly in Italy, Austria, and Germany in an online, preregistered study conducted about 50 days after the beginning of the COVID-19 outbreak in Europe. Images depicting individuals alone, in small groups (up to four people), and in large groups (more than seven people) were rated in terms of valence, arousal, and perceived physical distance. Pre-pandemic normative ratings were obtained from a validated database (OASIS). Several self-report measures were also taken, and condensed into four factors through factor analysis. All images were rated as more arousing compared to the pre-pandemic period, and the greater the decrease in real-life physical interactions reported by participants, the higher the ratings of arousal. As expected, only images depicting large gatherings of people were rated less positively during, compared to before, the pandemic. These ratings of valence were, however, moderated by a factor that included participants' number of days in isolation, relationship closeness, and perceived COVID-19 threat. Higher scores on this factor were associated with more positive ratings of images of individuals alone and in small groups, suggesting an increased appreciation of safer social situations, such as intimate and small-group contacts. The same factor was inversely related to the perceived physical distance between individuals in images of small and large groups, suggesting an impact of lockdown measures and contagion-related worries on the representation of interpersonal space. These findings point to rapid and compelling psychological and social consequences of the lockdown measures imposed during the COVID-19 pandemic on the perception of social groups. Further studies should assess the long-term impact of such events as typical everyday life is restored.

Primary motor cortex crucial for action prediction: A tDCS study.

The neural network underlying action observation - i.e., the action observation network - forms an anticipatory representation of observed actions. Although correlational studies suggest that the motor cortex (M1) might be involved in this anticipatory coding, it is unclear whether M1 is also causally essential for making accurate predictions about observed actions. To test the functional relevance of M1 to action prediction, we used offline monopolar transcranial direct current stimulation (tDCS). In four tDCS groups of healthy participants, we administered 15 min of anodal or cathodal constant currents of 1 or 2 mA over the left M1 before participants performed two tasks requiring them to make predictions about the outcomes of reaching-grasping human actions (Action Prediction - AP) or non-human movements (Non-human Prediction - NP). In each group, participants received sham and active tDCS in two separate sessions. We found that 2 mA cathodal tDCS (c-tDCS2mA) selectively impaired accuracy in the AP task, but not in the NP task. No change in performance was found following anodal or 1-mA tDCS protocols. Additionally, no change was found following c-tDCS2mA administered over a control site. These findings show task-, polarity-, intensity- and site-specific disruption of AP abilities following c-tDCS2mA over M1. Thus, our study establishes specific tDCS parameters for effective M1 stimulation in AP and highlights the functional relevance of the motor system to making accurate predictions about the outcomes of human actions.

The causal role of the somatosensory cortex in prosocial behaviour.

Witnessing another person's suffering elicits vicarious brain activity in areas that are active when we ourselves are in pain. Whether this activity influences prosocial behavior remains the subject of debate. Here participants witnessed a confederate express pain through a reaction of the swatted hand or through a facial expression, and could decide to reduce that pain by donating money. Participants donate more money on trials in which the confederate expressed more pain. Electroencephalography shows that activity of the somatosensory cortex I (SI) hand region explains variance in donation. Transcranial magnetic stimulation (TMS) shows that altering this activity interferes with the pain-donation coupling only when pain is expressed by the hand. High-definition transcranial direct current stimulation (HD-tDCS) shows that altering SI activity also interferes with pain perception. These experiments show that vicarious somatosensory activations contribute to prosocial decision-making and suggest that they do so by helping to transform observed reactions of affected body-parts into accurate perceptions of pain that are necessary for decision-making.

What neuromodulation and lesion studies tell us about the function of the mirror neuron system and embodied cognition.

We review neuromodulation and lesion studies that address how activations in the mirror neuron system contribute to our perception of observed actions. Past reviews showed disruptions of this parieto-premotor network impair imitation and goal and kinematic processing. Recent studies bring five new themes. First, focal perturbations of a node of that circuit lead to changes across all nodes. Second, primary somatosensory cortex is an integral part of this network suggesting embodied representations are somatosensory-motor. Third, disturbing this network impairs the ability to predict the actions of others in the close (∼300ms) future. Fourth, disruptions impair our ability to coordinate our actions with others. Fifth, disrupting this network, the insula or cingulate also impairs emotion recognition.

Visual, sensorimotor and cognitive routes to understanding others' enjoyment: An individual differences rTMS approach to empathic accuracy.

Functional imaging studies suggest that accurate understanding of others' emotional feelings (i.e., empathic accuracy, EA) recruits high-order visual, sensorimotor and mentalizing brain networks. However, the behavioral relevance of these findings is unclear. To fill in this gap, we used repetitive transcranial magnetic stimulation (rTMS) to interfere with the right superior temporal sulcus (STS), inferior frontal gyrus (IFG) and temporoparietal junction (TPJ) during an EA task requiring participants to infer the enjoyment felt by a social target while smiling/laughing. Relative to a baseline condition (sham rTMS), active rTMS of STS, IFG and TPJ (but not of a control site) disrupted the efficiency of EA task performance, mainly by lowering task accuracy; rTMS of IFG and TPJ also slowed down response speeds. Importantly, the effects of rTMS on EA task efficiency were predicted by baseline EA performance, with high-performers showing a performance decrease when the TPJ was targeted, and low-performers showing a performance decrease when the STS or the IFG was targeted. The double dissociation in the effect of rTMS between low- and high-performers suggests distinct roles of STS, IFG and TPJ in efficient understanding of the enjoyment felt by others. These findings provide causal evidence of distinct visual, sensorimotor and cognitive routes to EA and suggest that individual differences in EA are underpinned by differential recruitment of these routes.

Boosting and Decreasing Action Prediction Abilities Through Excitatory and Inhibitory tDCS of Inferior Frontal Cortex.

Influential theories suggest that humans predict others' upcoming actions by using their own motor system as an internal forward model. However, evidence that the motor system is causally essential for predicting others' actions is meager. Using transcranial direct current stimulation (tDCS), we tested the role of the inferior frontal cortex (IFC), in action prediction (AP). We devised a novel AP task where participants observed the initial phases of right-hand reaching-to-grasp actions and had to predict their outcome (i.e., the goal/object to be grasped). We found that suppression by cathodal (inhibitory) tDCS of the left IFC, but not the left superior temporal sulcus or the right IFC, selectively impaired performance on the AP task, but not on a difficulty-matched control task. Remarkably, anodal (excitatory) tDCS of the left IFC brought about a selective improvement in the AP task. These findings indicate that the left IFC is necessary for predicting the outcomes of observed human right-hand actions. Crucially, our study shows for the first time that down- and up-regulating excitability within the motor system can hinder and enhance AP abilities, respectively. These findings support predictive coding theories of action perception and have implications for enhancement of AP abilities.

Sensorimotor Network Crucial for Inferring Amusement from Smiles.

Understanding whether another's smile reflects authentic amusement is a key challenge in social life, yet, the neural bases of this ability have been largely unexplored. Here, we combined transcranial magnetic stimulation (TMS) with a novel empathic accuracy (EA) task to test whether sensorimotor and mentalizing networks are critical for understanding another's amusement. Participants were presented with dynamic displays of smiles and explicitly requested to infer whether the smiling individual was feeling authentic amusement or not. TMS over sensorimotor regions representing the face (i.e., in the inferior frontal gyrus (IFG) and ventral primary somatosensory cortex (SI)), disrupted the ability to infer amusement authenticity from observed smiles. The same stimulation did not affect performance on a nonsocial task requiring participants to track the smiling expression but not to infer amusement. Neither TMS over prefrontal and temporo-parietal areas supporting mentalizing, nor peripheral control stimulations, affected performance on either task. Thus, motor and somatosensory circuits for controlling and sensing facial movements are causally essential for inferring amusement from another's smile. These findings highlight the functional relevance of IFG and SI to amusement understanding and suggest that EA abilities may be grounded in sensorimotor networks for moving and feeling the body.

Pictures of disgusting foods and disgusted facial expressions suppress the tongue motor cortex.

The tongue holds a unique role in gustatory disgust. However, it is unclear whether the tongue representation in the motor cortex (tM1) is affected by the sight of distaste-related stimuli. Using transcranial magnetic stimulation (TMS) in healthy humans, we recorded tongue motor-evoked potentials (MEPs) as an index of tM1 cortico-hypoglossal excitability. MEPs were recorded while participants viewed pictures associated with gustatory disgust and revulsion (i.e. rotten foods and faces expressing distaste), non-oral-related disgusting stimuli (i.e. invertebrates like worms) and control stimuli. We found that oral-related disgust pictures suppressed tM1 cortico-hypoglossal output. This tM1 suppression was predicted by interindividual differences in disgust sensitivity. No similar suppression was found for disgusting invertebrates or when MEPs were recorded from a control muscle. These findings suggest that revulsion-eliciting food pictures trigger anticipatory inhibition mechanisms, possibly preventing toxin swallowing and contamination. A similar suppression is elicited when viewing distaste expressions, suggesting vicarious motor inhibition during social perception of disgust. Our study suggests an avoidant-defensive mechanism in human cortico-hypoglossal circuits and its 'resonant' activation in the vicarious experience of others' distaste. These findings support a role for the motor system in emotion-driven motor anticipation and social cognition.

Long-latency modulation of motor cortex excitability by ipsilateral posterior inferior frontal gyrus and pre-supplementary motor area.

The primary motor cortex (M1) is strongly influenced by several frontal regions. Dual-site transcranial magnetic stimulation (dsTMS) has highlighted the timing of early (<40 ms) prefrontal/premotor influences over M1. Here we used dsTMS to investigate, for the first time, longer-latency causal interactions of the posterior inferior frontal gyrus (pIFG) and pre-supplementary motor area (pre-SMA) with M1 at rest. A suprathreshold test stimulus (TS) was applied over M1 producing a motor-evoked potential (MEP) in the relaxed hand. Either a subthreshold or a suprathreshold conditioning stimulus (CS) was administered over ipsilateral pIFG/pre-SMA sites before the TS at different CS-TS inter-stimulus intervals (ISIs: 40-150 ms). Independently of intensity, CS over pIFG and pre-SMA (but not over a control site) inhibited MEPs at an ISI of 40 ms. The CS over pIFG produced a second peak of inhibition at an ISI of 150 ms. Additionally, facilitatory modulations were found at an ISI of 60 ms, with supra- but not subthreshold CS intensities. These findings suggest differential modulatory roles of pIFG and pre-SMA in M1 excitability. In particular, the pIFG -but not the pre-SMA- exerts intensity-dependent modulatory influences over M1 within the explored time window of 40-150 ms, evidencing fine-tuned control of M1 output.