Self-other Discrimination Research Articles

Effects of observing own/others hand movement in different perspectives on mu rhythm suppression: an EEG study

BackgroundPrevious studies have reported that the sense of “self” is associated with specific brain regions and neural network activities. In addition, the mirror system, which functions when executing or observing an action, might contribute to differentiating the self from others and form the basis of the sense of self as a fundamental physical representation. This study investigated whether differences in mu suppression, an indicator of mirror system activity, reflect cognitions related to self-other discrimination.MethodsThe participants were 30 of healthy college students. The participants observed short video clips of hand movements performed by themselves or actors from two perspectives (i.e., first-person and third-person). The electroencephalogram (EEG) mu rhythm (8–13 Hz) was measured during video observation as an index of mirror neuron system activity. EEG activity related to self-detection was analyzed using participants’ hand movements as self-relevant stimuli.ResultsThe results showed that mu suppression in the 8–13-Hz range exhibited perspective-dependent responses to self/other stimuli. There was a significant self-oriented mu suppression response in the first-person perspective. However, the study found no significant response orientation in the third-person perspective. The results suggest that mirror system activity may involve self-other discrimination differently depending on the perspective.ConclusionsIn summary, this study examined the mirror system’s activity for self and others using the EEG’s mu suppression. As a result, it was suggested that differences in self and others or perspectives may influence mu suppression.

Temporal Properties of Self-Prioritization.

Using electroencephalogram (EEG), we tested the hypothesis that the association of a neutral stimulus with the self would elicit ultra-fast neural responses from early top-down feedback modulation to late feedforward periods for cognitive processing, resulting in self-prioritization in information processing. In two experiments, participants first learned three associations between personal labels (self, friend, stranger) and geometric shapes (Experiment 1) and three colors (Experiment 2), and then they judged whether the shape/color-label pairings matched. Stimuli in Experiment 2 were shown in a social communicative setting with two avatars facing each other, one aligned with the participant's view (first-person perspective) and the other with a third-person perspective. The color was present on the t-shirt of one avatar. This setup allowed for an examination of how social contexts (i.e., perspective taking) affect neural connectivity mediating self-related processing. Functional connectivity analyses in the alpha band (8-12 Hz) revealed that self-other discrimination was mediated by two distinct phases of neural couplings between frontal and occipital regions, involving an early phase of top-down feedback modulation from frontal to occipital areas followed by a later phase of feedforward signaling from occipital to frontal regions. Moreover, while social communicative settings influenced the later feedforward connectivity phase, they did not alter the early feedback coupling. The results indicate that regardless of stimulus type and social context, the early phase of neural connectivity represents an enhanced state of awareness towards self-related stimuli, whereas the later phase of neural connectivity may be associated with cognitive processing of socially meaningful stimuli.

The discrimination of self from other as a component of empathy.

Despite the centrality of empathy in human social life, there is no widely agreed definition or characterization of the concept of empathy. A common thread in many of the proposed definitions, however, is that empathy presupposes the discrimination of self and other on the grounds that, to empathize with another individual, the mental state of the target individual must first be distinguished from the empathizer's own mental state. The purpose of this study is to investigate this proposal empirically. We employed a paradigm in which participants rated the emotional valence and degree of arousal of 93 facial expressions of mental states. We asked participants to infer the mental state represented by each facial expression (the Other condition) as well as to describe the effect of the expression on their own mental state (the Self condition). An absolute difference score between the Other and the Self conditions was used as an index of a capacity for self-other discrimination. Empathy was measured using the Interpersonal Reactivity Index. Results show that individuals high in trait empathy discriminate between self and other to a significantly greater degree when judging mental states than individuals low in trait empathy. This suggests that the capacity for self-other discrimination may be a component of the capacity for empathy and that future investigations of the concept of empathy ought to retain it. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Electrophysiological correlates of self-prioritization

Personally relevant stimuli exert a powerful influence on social cognition. What is not yet fully understood, however, is how early in the processing stream self-relevance influences decisional operations. Here we used a shape-label matching task in conjunction with electroencephalography and computational modeling to explore this issue. A theoretically important pattern of results was observed. First, a standard self-prioritization effect emerged indicating that responses to self-related items were faster and more accurate than responses to other-related stimuli. Second, a hierarchical drift diffusion model analysis revealed that this effect was underpinned by the enhanced uptake of evidence from self-related stimuli. Third, self-other discrimination during matching trials was observed at both early posterior N1 and late centro-parietal P3 components. Fourth, whereas the N1 was associated with the rate of information accumulation during decisional processing, P3 activity was linked with the evidential requirements of response selection. These findings elucidate the electrophysiological correlates of self-prioritization.

No self-advantage in recognizing photographs of one’s own hand: experimental and meta-analytic evidence

Visually recognising one’s own body is important both for controlling movement and for one’s sense of self. Twenty previous studies asked healthy adults to make rapid recognition judgements about photographs of their own and other peoples’ hands. Some of these judgements involved explicit self-recognition: “Is this your hand or another person’s?” while others assessed self-recognition implicitly, comparing performance for self and other hands in tasks unrelated to self-other discrimination (e.g., left-versus-right; match-to-sample). We report five experiments with three groups of participants performing left-versus-right (Experiment 1) and self-versus-other discrimination tasks (Experiments 2 to 5). No evidence was found for better performance with self than with other stimuli, but some evidence was found for a self-disadvantage in the explicit task. Manipulating stimulus duration as a proxy for task difficulty revealed strong response biases in the explicit self-recognition task. Rather than discriminating between self and other stimuli, participants seem to treat self-other discrimination tasks as self-detection tasks, raising their criterion and consistently responding ‘not me’ when the task is difficult. A meta-analysis of 21 studies revealed no overall self-advantage, and suggested a publication bias for reports showing self-advantages in implicit tasks. Although this may appear counter-intuitive, we suggest that there may be no self-advantage in hand recognition.

Mimetic Self-Reflexivity and Intersubjectivity in Complementary and Alternative Medicine Practices: The Mirror Neuron System in Breast Cancer Survivorship.

This study examines complementary and alternative medicine (CAM) providers’ practices in the treatment of their breast cancer survivor (BCS) clients and interprets these practices within the context of existing neuroscientific research on the mirror neuron system (MNS). Purposive and snowball sampling was conducted to recruit CAM providers (N = 15) treating BCSs from integrative medicine centers, educational institutions, private practices, and professional medical associations across the United States. In-depth semi-structured interviewing (N = 252 single-spaced pages) and inductive qualitative content analysis reveal CAM therapeutic practices emphasize a diachronic form of mimetic self-reflexivity and a serendipitous form of mimetic intersubjectivity in BCS pain management to allow the providers to tune-in to their clients’ internal states over time and experience themselves as an embodied subject in an imaginative, shared space. By employing imagination and an intentional vulnerability in their embodied simulation of the others’ internal states, CAM providers co-create experiences of pain while recognizing what about the other remains an unknown. Although MNs provide the mechanism for imitation and simulation underlying empathy through a neuronally wired grasp of the other’s intentionality, the study suggests that examining mimetic self-reflexivity and intersubjectivity in the therapeutic space may allow for a shared simulation of participants’ subjective experiences of pain and potentially inform research on self-recognition and self-other discrimination as an index of self-awareness which implicates the MNS in embodied social cognition in imaginative ways.

Your action does matter to me: Examining the role of the co-actor's action-effects in resolving the self-other discrimination problem.

Sharing a task with another person can introduce the need to discriminate representations that refer to our own action from that of the other person's. The current understanding is that information about the stimulus event drives the self-other discrimination process, as it promotes (via the reactivation of feature codes) the representation that encodes the corresponding action. However, this mechanistic explanation relies on experimental situations in which stimulus event information (e.g., spatial location) is always and directly available. Thus, it remains unclear whether and how we could successfully discriminate between self- and other related action representations in the absence of such information. The present study addressed this unanswered question using a novel joint Simon task-based paradigm. We report the results of three experiments in which we manipulated the availability of stimulus event information into the contralateral space. Our findings demonstrate that participants are able to compensate for the absence of stimulus event information by relying on temporal features of their co-actor's action-effects (Experiment 1). Even more surprising was that participants continued to monitor the temporal features of their co-actor's actions even when given a verbal signal by their co-actor (Experiments 2a), or full access to the common workspace (Experiment 2b). Our results are strong evidence that the representation of actions is not purely stimulus driven. They suggest that the temporal dimension of the other person's actions is able to drive the self-other discrimination process, in the same way as other perceptual dimensions and feature codes that are shared with the stimulus event.

Visual Hand Recognition in Hand Laterality and Self-Other Discrimination Tasks: Relationships to Autistic Traits and Positive Body Image.

In a study concerning visual body part recognition, a “self-advantage” effect, whereby self-related body stimuli are processed faster and more accurately than other-related body stimuli, was revealed, and the emergence of this effect is assumed to be tightly linked to implicit motor simulation, which is activated when performing a hand laterality judgment task in which hand ownership is not explicitly required. Here, we ran two visual hand recognition tasks, namely, a hand laterality judgment task and a self-other discrimination task, to investigate (i) whether the self-advantage emerged even if implicit motor imagery was assumed to be working less efficiently and (ii) how individual traits [such as autistic traits and the extent of positive self-body image, as assessed via the Autism Spectrum Quotient (AQ) and the Body Appreciation Scale-2 (BAS-2), respectively] modulate performance in these hand recognition tasks. Participants were presented with hand images in two orientations [i.e., upright (egocentric) and upside-down (allocentric)] and asked to judge whether it was a left or right hand (an implicit hand laterality judgment task). They were also asked to determine whether it was their own, or another person’s hand (an explicit self-other discrimination task). Data collected from men and women were analyzed separately. The self-advantage effect in the hand laterality judgment task was not revealed, suggesting that only two orientation conditions are not enough to trigger this motor simulation. Furthermore, the men’s group showed a significant positive correlation between AQ scores and reaction times (RTs) in the laterality judgment task, while the women’s group showed a significant negative correlation between AQ scores and differences in RTs and a significant positive correlation between BAS-2 scores and dprime in the self-other discrimination task. These results suggest that men and women differentially adopt specific strategies and/or execution processes for implicit and explicit hand recognition tasks.

Are you as important as me? Self-other discrimination within trait-adjective processing

Healthy adults typically display enhanced processing for self- (relative to other-) relevant and positive (relative to negative) information. However, it is unclear whether these two biases interact to form a self-positivity bias, whereby self-positive information receives prioritized processing. It is also unclear how a blocked versus mixed referent design impacts reference and valence processing. We addressed these questions using behavioral and electrophysiological indices across two studies using a Self-Referential Encoding Task, followed by surprise recall and recognition tasks. Early (P1) and late (LPP) event-related potentials were time-locked to a series of trait adjectives, encoded relative to oneself or a fictional character, with referent presented in a blocked (Exp. 1) or mixed (Exp. 2) trial design. Regardless of study design, participants recalled and recognized more self- than other-relevant adjectives, and recognized more positive than negative adjectives. Additionally, participants demonstrated larger LPP amplitudes for self-relevant and positive adjectives. The LPP self-relevance effect emerged earlier and persisted longer in the blocked (400–800 ms) versus mixed design (600–800 ms). The LPP valence effect was not apparent in the blocked design, but appeared late in the mixed design (600–1200 ms). Critically, the interaction between self-relevance and valence appeared only behaviorally in the mixed design, suggesting that overall self-relevance and valence independently impact neural socio-cognitive processing.

Sensorimotor Induction of Auditory Misattribution in Early Psychosis.

Dysfunction of sensorimotor predictive processing is thought to underlie abnormalities in self-monitoring producing passivity symptoms in psychosis. Experimentally induced sensorimotor conflict can produce a failure in bodily self-monitoring (presence hallucination [PH]), yet it is unclear how this is related to auditory self-monitoring and psychosis symptoms. Here we show that the induction of sensorimotor conflict in early psychosis patients induces PH and impacts auditory-verbal self-monitoring. Participants manipulated a haptic robotic system inducing a bodily sensorimotor conflict. In experiment 1, the PH was measured. In experiment 2, an auditory-verbal self-monitoring task was performed during the conflict. Fifty-one participants (31 early psychosis patients, 20 matched controls) participated in the experiments. The PH was present in all participants. Psychosis patients with passivity experiences (PE+) had reduced accuracy in auditory-verbal self-other discrimination during sensorimotor stimulation, but only when sensorimotor stimulation involved a spatiotemporal conflict (F(2, 44) = 6.68, P = .002). These results show a strong link between robotically controlled alterations in sensorimotor processing and auditory misattribution in psychosis and provide evidence for the role of sensorimotor processes in altered self-monitoring in psychosis.

Altered self-recognition in patients with schizophrenia

Self-alienation is a common characterization of various disturbing experiences in patients with schizophrenia. A vivid example comes from patient reports of not recognizing themselves when inspecting their specular image in the mirror. By applying the multisensory paradigm of the Enfacement Illusion, this study empirically addresses the specular Self-Other discrimination in patients with schizophrenia. 35 patients diagnosed with schizophrenia and 35 healthy matched controls were enrolled in the study. Results found that the group of patients with schizophrenia had a significant skewed self-other discrimination towards the other at baseline. Furthermore, the effect of visuo-tactile stimulation on self-recognition in the schizophrenia patients was significantly altered after both synchronous and asynchronous stimulation compared to baseline. This contrasted with healthy controls which in line with earlier studies only had significantly different self-recognition after synchronous stimulation. The study thus suggests that patients with schizophrenia have deviations in their specular self-recognition compared to healthy controls. Moreover, that temporal factors in multisensory integration may contribute to alterations of self-related stimuli in patients with schizophrenia.

Simultaneous EEG-NIRS Measurement of the Inferior Parietal Lobule During a Reaching Task With Delayed Visual Feedback.

We investigated whether the inferior parietal lobule (IPL) responds in real-time to multisensory inconsistency during movement. The IPL is thought to be involved in both the detection of inconsistencies in multisensory information obtained during movement and that obtained during self-other discrimination. However, because of the limited temporal resolution of conventional neuroimaging techniques, it is difficult to distinguish IPL activity during movement from that during self-other discrimination. We simultaneously conducted electroencephalography (EEG) and near-infrared spectroscopy (NIRS) with the goal of examining IPL activity with a high spatiotemporal resolution during single reaching movements. Under a visual feedback-delay condition, gamma event-related synchronization (γ-ERS), i.e., an increase in gamma (31–47 Hz) EEG power occurred during reaching movements. This γ-ERS is considered to reflect processing of information about prediction errors. To integrate this temporal information with spatial information from the NIRS signals, we developed a new analysis technique that enabled estimation of the regions that show a hemodynamic response characterized by EEG fluctuation present in the visual feedback-delay condition. As a result, IPL activity was explained by γ-ERS specific to visual feedback delay during movements. Thus, we succeeded in demonstrating real-time activation of the IPL in response to multisensory inconsistency. However, we did not find any correlation between either IPL activity or γ-ERS with the sense of agency. Therefore, our results suggest that while the IPL is influenced by prediction error signals, it does not engage in direct processing underlying the conscious experience of making a movement, which is the foundation of self-other discrimination.

Researches on empathy: Methodologies and characteristics from a psychophysiological perspective

Empathy is an essential skill in our social lives, allowing us to understand and share others’ feelings. In the last decade, empathy has been a hot topic in cognitive neuroscience for its important role in social interaction. To date, there are a variety of definitions of the term “empathy”, such as “a reaction to the observed experiences of another” and “the ability to experience and understand what others feel without confusion between oneself and others”. Based on different definitions of empathy, different methodologies have been developed and adopted in the field of empathy research. Valid empathy questionnaires are developed to provide ones’ subjective evaluation about their empathy ability (i.e., trait empathy); behavioral paradigms are designed to measure individuals’ empathy levels under a specific context (i.e., state empathy); physiological techniques and brain imaging techniques are useful in detecting objective physiological signals related to empathy. However, some findings on empathy are mixed and inconsistent, which might be due to the different definitions and methodologies adopted by each study. To deepen our understanding of empathy and its psychological mechanisms, it is necessary to integrate different methodologies and interpret results from different aspects. To this end, this review first summarized how empathy is typically measured and quantified at different measurement levels with an emphasis on emotional empathy and cognitive empathy, given that existing studies on empathy mainly focus on the two categories and their combination. Specifically, methodologies in empathy research were introduced as followed: (1) Widely-used empathy questionnaires, including the detailed definitions and measurement dimensions; (2) classic experimental materials and behavioral paradigms for measuring emotional empathy and/or cognitive empathy; (3) empathy-related physiological signals detected by facial electromyography, electroencephalography (EEG), magnetoencephalography (MEG), and magnetic resonance imaging (MRI). Next, we discussed the advantages and disadvantages of each methodology and pointed out the difficulties in compiling findings from studies using different methodologies. For example, different empathy questionnaires applied to the same group may yield contradictory results and the quality of experimental stimulus in the same kind of empathy paradigms potentially influences participants’ brain activities. More importantly, the physiological signals (e.g. event-related potential components) recorded in empathy experiments are not “specific” but only “related” to empathy. Then, we suggested that researchers should carefully select appropriate methodologies according to their research needs. For instance, EEG is suitable for exploring empathic processing in the time domain, while functional magnetic resonance imaging (fMRI) is conducive to pinpoint the specific functions (e.g. self-other discrimination) of empathy-related brain regions. Finally, we proposed that the conceptual framework of empathy should be unified and more naturalistic paradigms should be developed to reveal the interactions among different empathic subprocesses in the future. In conclusion, this review highlights the importance of comparing and combining different methodologies in order to reveal the underlying mechanisms of empathy, which yields new insights into social interaction.

Malleability of the self: electrophysiological correlates of the enfacement illusion

Self-face representation is fundamentally important for self-identity and self-consciousness. Given its role in preserving identity over time, self-face processing is considered as a robust and stable process. Yet, recent studies indicate that simple psychophysics manipulations may change how we process our own face. Specifically, experiencing tactile facial stimulation while seeing similar synchronous stimuli delivered to the face of another individual seen as in a mirror, induces ‘enfacement’ illusion, i.e. the subjective experience of ownership of the other’s face and a bias in attributing to the self, facial features of the other person. Here we recorded visual Event-Related Potentials elicited by the presentation of self, other and morphed faces during a self-other discrimination task performed immediately after participants received synchronous and control asynchronous Interpersonal Multisensory Stimulation (IMS). We found that self-face presentation after synchronous as compared to asynchronous stimulation significantly reduced the late positive potential (LPP; 450–750 ms), a reliable electrophysiological marker of self-identification processes. Additionally, enfacement cancelled out the differences in LPP amplitudes produced by self- and other-face during the control condition. These findings represent the first direct neurophysiological evidence that enfacement may affect self-face processing and pave the way to novel paradigms for exploring defective self-representation and self-other interactions.

Self-reflection and self-esteem: ERP study of explicit self vs. other evaluation

Face recognition is an apparently straightforward but, in fact, complex ability, encompassing the activation of at least visual and somatosensory representations. Understanding how identity shapes the interplay between these face-related affordances could clarify the mechanisms of self-other discrimination. To this aim, we exploited the so-called “face inversion effect” (FIE), a specific bias in the mental rotation of face images (of other people): with respect to inanimate objects, face images require longer time to be mentally rotated from the upside-down. Via the FIE, which suggests the activation of somatosensory mechanisms, we assessed identity-related changes in the interplay between visual and somatosensory affordances between self- and other-face representations. Methodologically, to avoid the potential interference of the somatosensory feedback associated with musculoskeletal movements, we introduced the tracking of gaze direction to record participants’ response. Response times from twenty healthy participants showed the larger FIE for self- than other-faces, suggesting that the impact of somatosensory affordances on mental representation of faces varies according to identity. The present study lays the foundations of a quantifiable method to implicitly assess self-other discrimination, with possible translational benefits for early diagnosis of face processing disturbances (e.g. prosopagnosia), and for neurophysiological studies on self-other discrimination in ethological settings.

Whose emotion is it? Measuring self-other discrimination in romantic relationships during an emotional evaluation paradigm.

In healthy subjects, emotional stimuli, positive stimuli in particular, are processed in a facilitated manner as are stimuli related to the self. These preferential processing biases also seem to hold true for self-related positive stimuli when compared to self-related negative or other-related positive stimuli suggesting a self-positivity bias in affective processing. The present study investigates the stability of this self-positivity bias and its possible extension to the emotional other in a sample of N = 147 participants including single participants (n = 61) and individuals currently in a romantic relationship (n = 86) reporting moderate to high levels of passionate love. Participants were presented a series of emotional and neutral words that could be related to the reader’s self (e.g., “my pleasure”, “my fear”), or to an insignificant third person, unknown to the reader (e.g., “his pleasure”, “his fear”) or devoid of any person reference (e.g., “the pleasure”, “the fear”). The task was to read the words silently and to evaluate the word pairs in reference to one’s own feelings elicited during reading. Results showed a self-positivity bias in emotional judgments in all participants, particularly in men. Moreover, participants in a romantic relationship (women and men) evaluated positive, other-related stimuli more often as valence-congruent with one’s own feelings than single participants. Taken together, these findings support the idea of a self-positivity bias in healthy subjects and an expansion of this bias while being in a romantic relationship.

The influence of passionate love on self-other discrimination during joint action.

Prior research on romantic relationships suggests that being in love involves a blurring of self-other cognitive boundaries. However, this research has focused so far on conceptual self-representation, related to the individual's traits or interests. The present study tested the hypothesis that passionate love involves a reduced discrimination between the self and the romantic partner at a bodily level, as indexed by an increased Joint Simon effect (JSE), and we further examined whether this self-other discrimination correlated with the passion felt for the partner. As predicted, we found an increased JSE when participants performed the Joint Simon Task with their romantic partner compared with a friend of the opposite sex. Providing support for the self-expansion model of love (Aron and Aron in Pers Relatsh 3(1):45-58, 1996), this result indicates that romantic relationships blur the boundaries between the self and the romantic partner at a bodily level. Furthermore, the strength of romantic feelings was positively correlated with the magnitude of the JSE when sharing the task with the romantic partner.

Self-Reference Emerges Earlier than Emotion during an Implicit Self-Referential Emotion Processing Task: Event-Related Potential Evidence.

Self-referential emotion refers to the process of evaluating emotional stimuli with respect to the self. Processes indicative of a self-positivity bias are reflected in electroencephalogram (EEG) signals at ~400 ms when the task does not require a discrimination of self from other. However, when distinguishing between self-referential and other-referential emotions is required, previous studies have shown inconsistent temporal dynamics of EEG signals in slightly different tasks. Based on the observation of early self–other discrimination, we hypothesized that self would be rapidly activated in the early stage to modulate emotional processing in the late stage during an implicit self-referential emotion. To test this hypothesis, we employed an implicit task in which participants were asked to judge the order of Chinese characters of trait adjectives preceded by a self (“I”) or other pronoun (“He” or “She”). This study aimed to explore the difference of social-related emotional evaluation from self-reference; the other pronoun was not defined to a specific person, rather it referred to the general concept. Sixteen healthy Chinese subjects participated in the experiment. Event-related potentials (ERPs) showed that there were self-other discrimination effects in the N1 (80–110 ms) and P1 (170–200 ms) components in the anterior brain. The emotional valence was discriminated in the later component of N2 (220–250 ms). The interaction between self-reference and emotional valence occurred during the late positive potential (LPP; 400–500 ms). Moreover, there was a positive correlation between response time (RT) and N1 in the self-reference condition based on the positive-negative contrast, suggesting a modulatory effect of the self-positivity bias. The results indicate that self-reference emerges earlier than emotion and then combines with emotional processing in an implicit task. The findings extend the view that the self plays a highly integrated and modulated role in self-referential emotion processing.

Implicit self-other discrimination affects the interplay between multisensory affordances of mental representations of faces

Face recognition is an apparently straightforward but, in fact, complex ability, encompassing the activation of at least visual and somatosensory representations. Understanding how identity shapes the interplay between these face-related affordances could clarify the mechanisms of self-other discrimination. To this aim, we exploited the so-called “face inversion effect” (FIE), a specific bias in the mental rotation of face images (of other people): with respect to inanimate objects, face images require longer time to be mentally rotated from the upside-down. Via the FIE, which suggests the activation of somatosensory mechanisms, we assessed identity-related changes in the interplay between visual and somatosensory affordances between self- and other-face representations. Methodologically, to avoid the potential interference of the somatosensory feedback associated with musculoskeletal movements, we introduced the tracking of gaze direction to record participants’ response. Response times from twenty healthy participants showed the larger FIE for self- than other-faces, suggesting that the impact of somatosensory affordances on mental representation of faces varies according to identity. The present study lays the foundations of a quantifiable method to implicitly assess self-other discrimination, with possible translational benefits for early diagnosis of face processing disturbances (e.g. prosopagnosia), and for neurophysiological studies on self-other discrimination in ethological settings.

The Medial Frontal Cortex Mediates Self-Other Discrimination in the Joint Simon Task

Abstract. Interacting with other individuals confronts cognitive control systems with the problem of how to distinguish between self-generated (internally triggered) and other-generated (externally triggered) action events. Recent neuroscience studies identified two core brain regions, the anterior medial frontal cortex (aMFC) and the right temporo-parietal junction (rTPJ), to be potentially involved in resolving this problem either by enhancing self-generated versus other-generated event representations (via aMFC) and/or by inhibiting event representations that are externally triggered (via rTPJ). Using transcranial direct current stimulation (tDCS), we investigated the role of the aMFC and the rTPJ for the online control of self-generated versus other-generated event representations in a joint Simon task. In two experimental sessions, participants received anodal, cathodal, or sham tDCS (1 mA intensity applied for 20 min), while performing an auditory joint Simon task. In addition to a general performance enhancement during cathodal (inhibitory) and anodal (excitatory) stimulation with increased practice, we found a significantly increased joint Simon effect (JSE) during cathodal stimulation of the aMFC (Experiment 1), as compared to sham stimulation. No modulation of the JSE was found during stimulation of the rTPJ (Experiment 2). By enhancing self-generated event representations the aMFC seems to be crucially involved in resolving the self-other discrimination problem in the joint Simon task.