Predicting and coding sound into action translation in spinal cord injured people.

Motor activation in response to perception of action-related stimuli may depend on a resonance mechanism subserving action understanding. The extent to which this mechanism is innate or learned from sensorimotor experience is still unclear. Here, we recorded EEG while people with paraplegia or tetraplegia consequent to spinal cord injury (SCI) and healthy control participants were presented with action sounds produced by body parts (mouth, hands or feet) that were or were not affected by SCI. Non-action sounds were used as further control. We observed reduced brain activation in subjects affected by SCI at both pre- and post-stimulus latencies specifically for those actions whose effector was disconnected by the spinal lesion (i.e., hand sound for tetraplegia and leg sound for both paraplegia and tetraplegia). Correlation analyses showed that these modulations were functionally linked with the chronicity of the lesion, indicating that the longer the time the lesion- EEG data acquisition interval and/or the more the lesion occurred at a young age, the weaker was the cortical activity in response to these action sounds. Tellingly, source estimations confirmed that these modulations originated from a deficit in the motor resonance mechanism, by showing diminished activity in premotor (during prediction and perception) and near the primary motor (during perception) areas. Such dissociation along the cortical hierarchy is consistent with both previous reports in healthy subjects and with hierarchical predictive coding accounts. Overall, these data expand on the notion that sensorimotor experience maintains the cortical representations relevant to anticipate and perceive action-related stimuli.

Topographic mapping of the sensorimotor qualities of empathic reactivity: A psychophysiological study in people with spinal cord injuries.

The experience of empathy for pain is underpinned by sensorimotor and affective dimensions which, although interconnected, are at least in part behaviorally and neurally distinct. Spinal cord injuries (SCI) induce a massive, below-lesion level, sensorimotor body-brain disconnection. This condition may make it possible to test whether sensorimotor deprivation alters specific dimensions of empathic reactivity to observed pain. To explore this issue, we asked SCI people with paraplegia and healthy controls to observe videos of painful or neutral stimuli administered to a hand (intact) or a foot (deafferented). The stimuli were displayed by means of a virtual reality set-up and seen from a first person (1PP) or third person (3PP) visual perspective. A number of measures were recorded ranging from explicit behaviors like explicit verbal reports on the videos, to implicit measures of muscular activity (like EMG from the corrugator and zygomatic muscles that may represent a proxy of sensorimotor empathy) and of autonomic reactivity (like the electrodermal response and Respiratory Sinus Arrhythmia that may represent a general proxy of affective empathy). While no across group differences in explicit verbal reports about the pain stimuli were found, SCI people exhibited reduced facial muscle reactivity to the stimuli applied to the foot (but not the hand) seen from the 1PP. Tellingly, the corrugator activity correlated with SCI participants' neuropathic pain. There were no across group differences in autonomic reactivity suggesting that SCI lesions may affect sensorimotor dimensions connected to empathy for pain.

Feeling of Ownership over an Embodied Avatar's Hand Brings About Fast Changes of Fronto-Parietal Cortical Dynamics.

When we look at our body parts, we are immediately aware that they belong to us and we rarely doubt about the integrity, continuity, and sense of ownership of our body. Despite this certainty, immersive virtual reality (IVR) may lead to a strong feeling of embodiment over an artificial body part seen from a first-person perspective (1PP). Although such feeling of ownership (FO) has been described in different situations, it is not yet understood how this phenomenon is generated at neural level. To track the real-time brain dynamics associated with FO, we delivered transcranial magnetic stimuli over the hand region in the primary motor cortex (M1) and simultaneously recorded electroencephalography (EEG) in 19 healthy volunteers (11 male/8 female) watching IVR renderings of anatomically plausible (full-limb) versus implausible (hand disconnected from the forearm) virtual limbs. Our data show that embodying a virtual hand is temporally associated with a rapid drop of cortical activity of the onlookers' hand region in the M1 contralateral to the observed hand. Spatiotemporal analysis shows that embodying the avatar's hand is also associated with fast changes of activity within an interconnected fronto-parietal circuit ipsilateral to the brain stimulation. Specifically, an immediate reduction of connectivity with the premotor area is paralleled by an enhancement in the connectivity with the posterior parietal cortex (PPC) which is related to the strength of ownership illusion ratings and thus likely reflects conscious feelings of embodiment. Our results suggest that changes of bodily representations are underpinned by a dynamic cross talk within a highly-plastic, fronto-parietal network.SIGNIFICANCE STATEMENT Observing an avatar's body part from a first-person perspective (1PP) induces an illusory embodiment over it. What remains unknown are the cortical dynamics underpinning the embodiment of artificial agents. To shed light on the physiological mechanisms of embodiment we used a novel approach that combines noninvasive stimulation of the cortical motor-hand area and whole-scalp electroencephalographic (EEG) recordings in people observing an embodied artificial limb. We found that just before the illusion started, there is a decrease of activity of the motor-hand area accompanied by an increase of connectivity with the parietal region ipsilateral to the stimulation that reflects the ratings of the embodiment illusion. Our results suggest that changes of bodily representations are underpinned by a dynamic cross talk within a fronto-parietal circuit.

The thermoception task: a thermal imaging-based procedure for measuring awareness of changes in peripheral body temperature.

Although thermal body signals provide crucial information about the state of an organism and changes in body temperature may be a sign of affective states (e.g., stress, pain, sexual arousal), research on thermal awareness is limited. Here we developed a task measuring awareness of changes in peripheral body temperature (thermal interoception) and compared it to the classical heartbeat counting task (cardiac interoception). With an infrared light bulb we delivered stimuli of different temperature intensities to the right hand of 31 healthy participants. Thermal interoceptive accuracy, i.e., the difference between participants' real and perceived change in hand temperature, showed good interindividual variability. We found that thermal interoception did not correlate with (and was generally higher than) cardiac interoception, suggesting that different interceptive channels provide separate contributions to awareness of bodily states. Moreover, the results hint at the great salience of thermal signals and the need for thermoregulation in day-to-day life. Finally, thermal interoceptive accuracy was associated with self-reported awareness of body temperature changes and with the ability to regulate distress by focusing on body sensations. Our task has the potential to significantly increase current knowledge about the role of interoception in cognition and behavior, particularly in social and emotional contexts.NEW & NOTEWORTHY We developed a novel task measuring awareness of changes in peripheral body temperature (i.e., thermal interoception). To avoid tactile confounds present in existing thermoceptive tasks, we used an infrared light bulb to deliver stimuli of different temperature intensities to the hand of participants and asked them to judge the perceived change in their hand temperature. Performance in the task showed good interindividual variability, did not correlate with cardiac interoceptive tasks, and was associated with self-reported thermosensitivity.

The performance monitoring system is attuned to others' actions during dyadic motor interactions.

Interpersonal motor interactions require the simultaneous monitoring of one's own and one's partner's actions. To characterize how the action monitoring system tracks self and other behavior during synchronous interactions, we combined electroencephalography recordings and immersive virtual reality in two tasks where participants were asked to synchronize their actions with those of a virtual partner (VP). The two tasks differed in the features to be monitored: the Goal task required participants to predict and monitor the VP's reaching goal; the Spatial task required participants to predict and monitor the VP's reaching trajectory. In both tasks, the VP performed unexpected movement changes to which the participant needed to adapt. By extracting the neural activity locked to the detection of unexpected changes in the VP's action (other-monitoring) or to the participants' action-replanning (self-monitoring), we show that the monitoring system is more attuned to others' than to one's own actions. Additionally, distinctive neural responses to VP's unexpected goals and trajectory corrections were found: goal changes were reflected both in early fronto-central and later posterior neural responses while trajectory deviations were reflected only in later posterior responses. Altogether, our results indicate that the monitoring system adopts an inherent social mode to handle interpersonal motor interactions.

The inside of me: interoceptive constraints on the concept of self in neuroscience and clinical psychology.

Humans are unique in their ability to think about themselves and carry a more or less clear notion of who they are in their mind. Here we review recent evidence suggesting that the birth, maintenance, and loss of the abstract concept of 'self' is deeply tied to interoception, the sense of internal physiological signals. Interoception influences multiple facets of the self-concept, cutting across its material, social, moral, and agentive components. Overall, we argue that interoception contributes to the stability of the self-concept over time, unifying its layers and constraining the degree to which it is susceptible to external influences. Hence, the core features of the self-concept are those that correlate more with inner bodily states. We discuss the implications that this may have for theories of embodied cognition as well as for the understanding of psychiatric disorders in which the concept of self appears fragmented or loose. Finally, we formulate some empirical predictions that could be tested in future studies to shed further light on this emerging field.

Inhibitory Theta Burst Stimulation Highlights the Role of Left aIPS and Right TPJ during Complementary and Imitative Human-Avatar Interactions in Cooperative and Competitive Scenarios.

Competitive and cooperative interactions are based on anticipation or synchronization with the partner's actions. Both forms of interaction may either require performing imitative or complementary movements with respect to those performed by our partner. We explored how parietal regions involved in the control of imitative behavior (temporo-parietal junction, TPJ), goal coding and visuo-motor integration (anterior intraparietal sulcus, aIPS) contribute to the execution of imitative and complementary movements during cooperative and competitive interactions. To this aim, we delivered off-line non-invasive inhibitory brain stimulation to healthy individuals' left aIPS and right TPJ before they were asked to reach and grasp an object together with a virtual partner by either performing imitative or complementary interactions. In different blocks, participants were asked to compete or cooperate with the virtual partner that varied its behavior according to cooperative or competitive contexts. Left aIPS and right TPJ inhibition impaired individuals' performance (i.e., synchrony in cooperative task and anticipation in competition) during complementary and imitative interactions, respectively, in both cooperative and competitive contexts, indicating that aIPS and TPJ inhibition affects own-other action integration and action imitation (that are different in complementary vs imitative interactions) more than action synchronization or anticipation (that are different in cooperative vs competitive contexts).

Visual feedback from a virtual body modulates motor illusion induced by tendon vibration.

Frequency-specific tendon vibration (TV) elicits illusory kinesthetic sensations around the vibrated body parts. Studies indicate that vision plays a fundamental role in modulating such illusions. In our current study, we used immersive virtual reality (IVR) to investigate the role of body-related visual feedback in modulating illusory sensation of movement in the left arm. Thirty healthy participants were asked to evaluate the onset of motor illusion and four illusion-related features (vividness, duration, extension and aftereffect), in the presence and absence of real and virtual visual feedback. Additionally, subjective reports of the embodiment illusion (the sense of embodying a virtual surrogate) were collected in virtual conditions. Results showed a progressive decrease in the perception of the motor illusion along a continuum ranging from the absence of visual feedback (maximal illusory perception) to the observation of one's own real arm (minimal illusory perception). Interestingly, the appearance of the virtual limbs affected the movement illusion differently. Specifically, TV evoked a stronger kinesthetic illusion when observing the virtual hand detached from the limb than during the observation of the virtual full limb and virtual object. This suggests that a closer visual resemblance between the virtual and real limb results in a greater effect on proprioceptive processing. However, no significant correlation was found between the illusion of arm movement and the illusion of embodiment, indicating that the two phenomena may not be directly related. These findings provide new insight into the role of body-related visual feedback in modulating motor illusions.

Freedom to act enhances the sense of agency, while movement and goal-related prediction errors reduce it.

The Sense of Agency (SoA) is the experience of controlling one's movements and their external consequences. Accumulating evidence suggests that freedom to act enhances SoA, while prediction errors are known to reduce it. Here, we investigated if prediction errors related to movement or to the achievement of the goal of the action exert the same influence on SoA during free and cued actions. Participants pressed a freely chosen or cued-colored button, while observing a virtual hand moving in the same or in the opposite direction-i.e., movement-related prediction error-and pressing the selected or a different color-i.e., goal-related prediction error. To investigate implicit and explicit components of SoA, we collected indirect (i.e., Synchrony Judgments) and direct (i.e., Judgments of Causation) measures. We found that participants judged virtual actions as more synchronous when they were free to act. Additionally, movement-related prediction errors reduced both perceived synchrony and judgments of causation, while goal-related prediction errors impaired exclusively the latter. Our results suggest that freedom to act enhances SoA and that movement and goal-related prediction errors lead to an equivalent reduction of SoA in free and cued actions. Our results also show that the influence of freedom to act and goal achievement may be limited, respectively, to implicit and explicit SoA, while movement information may affect both components. These findings provide support to recent theories that view SoA as a multifaceted construct, by showing that different action cues may uniquely influence the feeling of control.

Body ownership as a proxy for individual and social separation and connection.

Lee and Schwartz procedures of separation offer a much needed interpretation of the literature on moral cleansing. However, body ownership as a grounded mechanism of separation and connection has been neglected. We argue that embodiment may be employed to connect the self to desirable aspects of cognitive and emotional interactions and disembodiment to disconnect from undesirable elements.

Modulation of preference for abstract stimuli following competence-based social status primes.

In the present study, we measured whether competence-related high and low social status attributed to two unknown individuals affects participants' implicit reactivity to abstract stimuli associated to the identity of the same individuals. During a status-inducing procedure, participants were asked to play an interactive game with two (fake) players coded as high vs low status based on their game competence. Before and after the game, a modified version of the Affective Misattribution Procedure (AMP) was administered in which the players' faces were used as primes. The evaluation target, as is typical to AMP, was a Chinese ideogram. There were two different presentation timings for the prime image: 75 ms and 17 ms. After the status-inducing procedure, the evaluation targets preceded by the high-status prime (i.e. best player's face) were rated as more pleasant than those preceded by the low-status prime (i.e. worst player's face). This effect was only found, however, for the 75 ms lasting prime. Moreover, explicit ratings of the primes showed that the high-status player was rated as more intelligent, competent and dominant than the low status one. These results indicate that implicit preference and explicit evaluation of unacquainted individuals are rapidly modulated by competence-based social status attribution, thus hinting at the plastic nature of social categorization and, relatedly, the malleability of visual preference.

Visuo-motor interference with a virtual partner is equally present in cooperative and competitive interactions.

Automatic imitation of observed actions is thought to be a powerful mechanism, one that may mediate the reward value of interpersonal interactions, but that could also generate visuo-motor interference when interactions involve complementary movements. Since interpersonal coordination seems to be crucial both when cooperating and competing with others, the questions arises as to whether imitation-and thus visuo-motor interference-occurs in both scenarios. To address this issue, we asked human participants to engage in high- or low-interactive (Interactive or Cued condition, respectively), cooperative or competitive, joint reach-to-grasps with a virtual partner. More specifically, interactions occurred in: (i) a Cued condition, where participants simply adapted their movement timing to synchronize with (during cooperation) or anticipate (during competition) the virtual partner's grasp; (ii) an Interactive condition requiring the same adaptation, as well as a real-time selection of their action according to the virtual character's movement. To simulate a realistic human-human interaction, the virtual character would change its movement speed in consecutive trials according to participants' behaviour. Results demonstrate that visuo-motor interference-as indexed by movement kinematics (higher maximum wrist height during complementary compared to imitative power grips)-emerge in both cooperative and competitive motor interactions only when predictions about the partner's movements are needed to perform one's own action (interactive condition). These results support the idea that simulative imitation is heavily present when individuals need to match their behaviours closely.

Physiological and behavioral reactivity to social exclusion: a functional infrared thermal imaging study in patients with psoriasis.

Recent studies have shown that sympathetic nervous system (SNS) activity can be heavily impacted not only by basic threats to survival but also by threats to social bonds. In this study we explored the behavioral and physiological consequences of social exclusion/inclusion in patients with psoriasis, a disease frequently associated with the experience of being ostracized and with deficient emotion regulation skills. We employed a virtual ball-tossing game (Cyberball) to induce the experience of social exclusion/inclusion. We then used a Trust Game to measure the effects of this social modulation on trust. During Cyberball, infrared thermal imaging was used to record participants' facial temperature and thus obtain an online measure of SNS activation. Behavioral data showed that social exclusion shifted participants' trust toward unfamiliar players who had not previously excluded them. Physiological data indicated that in control participants, social exclusion triggered higher SNS activation than inclusion. No such effect was found in patients with psoriasis, whose SNS activity was the same during inclusion as it was during exclusion, suggesting that they benefit less from inclusive experiences than control participants. In addition, in patients but not in controls, higher SNS activation during social exclusion was linked to higher monetary investment toward unfamiliar players, a result in keeping with the social reconnection hypothesis, according to which emotions triggered by social rejection can be regulated by investing in new social interactions. We also found that an increase in periorbital temperature is accompanied by a decrease in happiness ratings after social exclusion was experienced during the Cyberball game. NEW & NOTEWORTHY Previous research on emotional processes in psoriasis has mainly employed self-report measures. In this study we used thermal imaging to obtain an online measure of the sympathetic nervous system (SNS) activity during social exclusion and tested how this experience influenced subsequent trust. We found that being included was a less positive experience for patients compared with controls and that SNS activity during exclusion had a stronger influence on subsequent trust in patients than in controls.

Cognitive load and emotional processing in psoriasis: a thermal imaging study.

Psoriasis is a chronic dermatologic disease which is frequently associated with psychological distress. Although studies suggest a relationship between this condition and difficulties in emotion regulation, behavioral and physiological evidence about this link is scarce. We measured implicit emotion regulation abilities of psoriasis patients and a healthy control group by examining the impact of distracting emotional (positive, negative or neutral) images on a working memory task ("Emotional N-Back") which could present high (2-back) or low (1-back) cognitive workload. Moreover, we used Functional Infrared Thermal Imaging to record participants' facial temperature and obtain a measure of the activation of the autonomic system. Rising of temperature over the peri-orbital areas and the nose tip are believed to reflect the activation and the de-activation of the sympathetic system, respectively. Patients scored higher than controls on the "Lack of emotional clarity" sub-scale of the Difficulties in Emotion Regulation Scale. Compared to controls, who performed much better in the low vs. high cognitive load condition, patients showed a smaller accuracy difference between the two conditions. Moreover, patients showed less sympathetic (lower peri-orbital and higher nasal tip temperature) activity (especially in the negative and neutral blocks) during the high vs. low cognitive load condition, suggesting that the former condition might be less emotionally demanding for them. Patients benefit more than controls from the load-dependent interference effect when dealing with emotional information; thus, therapeutic techniques aiming at teaching how to use cognitive strategies to downregulate emotions might be particularly appropriated for them.

Embodying their own wheelchair modifies extrapersonal space perception in people with spinal cord injury.

Despite the many links between body representation, acting and perceiving the environment, no research has to date explored whether specific tool embodiment in conditions of sensorimotor deprivation influences extrapersonal space perception. We tested 20 spinal cord injured (SCI) individuals to investigate whether specific wheelchair embodiment interacts with extrapersonal space representation. As a measure of wheelchair embodiment, we used a Body View Enhancement Task in which participants (either sitting in their own wheelchair or in one which they had never used before) were asked to respond promptly to flashing lights presented on their above- and below-lesion body parts. Similar or slower reaction times (RT) to stimuli on the body and wheelchair indicate, respectively, the presence or absence of tool embodiment. The RTs showed that the participants embodied their own wheelchair but not the other one. Moreover, they coded their deprived lower limbs as external objects and, when not in their own wheelchair, also showed disownership of their intact upper limbs. To measure extrapersonal space perception, we used a novel, ad hoc designed paradigm in which the participants were asked to observe a 3D scenario by means of immersive virtual reality and estimate the distance of a flag positioned on a ramp. In healthy subjects, errors in estimation increased as the distance increased, suggesting that they mentally represent the physical distance. The same occurred with the SCI participants, but only when they were in their own wheelchair. The results demonstrate for the first time that tool embodiment modifies extrapersonal space estimations.

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.

Error, rather than its probability, elicits specific electrocortical signatures: a combined EEG-immersive virtual reality study of action observation.

Detecting errors in one's own actions, and in the actions of others, is a crucial ability for adaptable and flexible behavior. Studies show that specific EEG signatures underpin the monitoring of observed erroneous actions (error-related negativity, error positivity, mid-frontal theta oscillations). However, the majority of studies on action observation used sequences of trials where erroneous actions were less frequent than correct actions. Therefore, it was not possible to disentangle whether the activation of the performance monitoring system was due to an error, as a violation of the intended goal, or to a surprise/novelty effect, associated with a rare and unexpected event. Combining EEG and immersive virtual reality (IVR-CAVE system), we recorded the neural signal of 25 young adults who observed, in first-person perspective, simple reach-to-grasp actions performed by an avatar aiming for a glass. Importantly, the proportion of erroneous actions was higher than correct actions. Results showed that the observation of erroneous actions elicits the typical electrocortical signatures of error monitoring, and therefore the violation of the action goal is still perceived as a salient event. The observation of correct actions elicited stronger alpha suppression. This confirmed the role of the alpha-frequency band in the general orienting response to novel and infrequent stimuli. Our data provide novel evidence that an observed goal error (the action slip) triggers the activity of the performance-monitoring system even when erroneous actions, which are, typically, relevant events, occur more often than correct actions and thus are not salient because of their rarity. NEW & NOTEWORTHY Activation of the performance-monitoring system (PMS) is typically investigated when errors in a sequence are comparatively rare. However, whether the PMS is activated by errors per se or by their infrequency is not known. Combining EEG-virtual reality techniques, we found that observing frequent (70%) action errors performed by avatars elicits electrocortical error signatures suggesting that deviation from the prediction of how learned actions should correctly deploy, rather than its frequency, is coded in the PMS.

Violation of expectations about movement and goal achievement leads to Sense of Agency reduction.

The control of one's own movements and of their impact on the external world generates a feeling of control referred to as Sense of Agency (SoA). SoA is experienced when actions match predictions and is reduced by unpredicted events. The present study investigated the contribution of monitoring two fundamental components of action-movement execution and goal achievement-that have been most often explored separately in previous research. We have devised a new paradigm in which participants performed goal-directed actions while viewing an avatar's hand in a mixed-reality scenario. The hand performed either the same action or a different one, simultaneously or after various delays. Movement of the virtual finger and goal attainment were manipulated, so that they could match or conflict with the participants' expectations. We collected judgments of correspondence (an explicit index of SoA that overcomes the tendency to over-attribute actions to oneself) by asking participants if the observed action was synchronous or not with their action. In keeping with previous studies, we found that monitoring both movement execution and goal attainment is relevant for SoA. Moreover, we expanded previous findings by showing that movement information may be a more constant source of SoA modulation than goal information. Indeed, an incongruent movement impaired SoA irrespective of delay duration, while a missed goal did so only when delays were short. Our novel paradigm allowed us to simultaneously manipulate multiple action features, a characteristic that makes it suitable for investigating the contribution of different sub-components of action in modulating SoA in healthy and clinical populations.

Embodying Others in Immersive Virtual Reality: Electro-Cortical Signatures of Monitoring the Errors in the Actions of an Avatar Seen from a First-Person Perspective.

Brain monitoring of errors in one's own and other's actions is crucial for a variety of processes, ranging from the fine-tuning of motor skill learning to important social functions, such as reading out and anticipating the intentions of others. Here, we combined immersive virtual reality and EEG recording to explore whether embodying the errors of an avatar by seeing it from a first-person perspective may activate the error monitoring system in the brain of an onlooker. We asked healthy participants to observe, from a first- or third-person perspective, an avatar performing a correct or an incorrect reach-to-grasp movement toward one of two virtual mugs placed on a table. At the end of each trial, participants reported verbally how much they embodied the avatar's arm. Ratings were maximal in first-person perspective, indicating that immersive virtual reality can be a powerful tool to induce embodiment of an artificial agent, even through mere visual perception and in the absence of any cross-modal boosting. Observation of erroneous grasping from a first-person perspective enhanced error-related negativity and medial-frontal theta power in the trials where human onlookers embodied the virtual character, hinting at the tight link between early, automatic coding of error detection and sense of embodiment. Error positivity was similar in 1PP and 3PP, suggesting that conscious coding of errors is similar for self and other. Thus, embodiment plays an important role in activating specific components of the action monitoring system when others' errors are coded as if they are one's own errors. SIGNIFICANCE STATEMENT: Detecting errors in other's actions is crucial for social functions, such as reading out and anticipating the intentions of others. Using immersive virtual reality and EEG recording, we explored how the brain of an onlooker reacted to the errors of an avatar seen from a first-person perspective. We found that mere observation of erroneous actions enhances electrocortical markers of error detection in the trials where human onlookers embodied the virtual character. Thus, the cerebral system for action monitoring is maximally activated when others' errors are coded as if they are one's own errors. The results have important implications for understanding how the brain can control the external world and thus creating new brain-computer interfaces.

Brain activity induced by implicit processing of others' pain and pleasure.

Studies indicate that both explicit and implicit processing of affectively charged stimuli may be reflected in specific behavioural markers and physiological signatures. Here, we investigated whether the pleasantness ratings of a neutral target were affected by the subliminal perception of a painful (a slap) or pleasant (a caress) touch delivered to others. In particular, we combined the continuous flash suppression technique with the affective misattribution procedure to explore subliminal processing of observed pain and pleasure in others. Results show that participants rated the neutral target as more or less likeable depending on whether they were subliminally primed with the pleasant or painful facial expression, respectively. The fMRI activity associated with painful and pleasant subliminal priming was mainly present in the anterior prefrontal cortex and the primary sensorimotor cortex, respectively. Thus, our study provides behavioural and neuro-physiological evidence that: (i) emotional reactivity toward positive or negative states of others can occur at an entirely subliminal level; (ii) specific neural substrates underpin reactivity to positive- and negative-valence of social emotions. Hum Brain Mapp 38:5562-5576, 2017. © 2017 Wiley Periodicals, Inc.