Gut markers of bodily self-consciousness in men.

Bodily self-consciousness, the state of mind that allows humans to be aware of their own body, forms the backdrop for almost every human experience, yet its underpinnings remain elusive. Here we combine an ingestible, minimally invasive capsule with surface electrogastrography to probe if gut physiology correlates with bodily self-consciousness in a sample of healthy men during a virtual bodily illusion. We discover that specific patterns of stomach and bowel activity (temperature, pressure, and pH) covary with specific facets of bodily self-consciousness (feelings of body location, agency, and disembodiment). These results uncover the hitherto untapped potential of minimally invasive probes to study the link between mental and gut states and show the significance of deep visceral organs in the self-conscious perception of ourselves as embodied beings.

Anosognosia for limb and bucco-facial apraxia as inferred from the recognition of gestural errors.

Anosognosia is a multifaceted syndrome characterized by a lack of awareness of motor, cognitive, or emotional deficits. While most studies have focused on basic motor disorders such as hemiplegia, only recently, the issue of whether anosognosia also concerns higher-order motor disorders like apraxia has been addressed. Here, we explore the existence of a specific form of anosognosia for apraxia in forty patients with uni-hemispheric vascular lesions. The patients were requested to imitate actions involving upper limb or bucco-facial body parts and then judge their performance. Successively, they were also asked to observe video recordings of the same actions performed by themselves or by other patients and judge the accuracy of the displayed actions. The comparison of participants versus examiner judgement and between error recognition of others' versus self's actions was considered as an index of awareness deficit for the online and offline conditions, respectively. Evidence was found that awareness deficits occurred both immediately after action execution (online anosognosia) and in the video recording task (offline anosognosia). Moreover, bucco-facial and limb apraxic patients were specifically unaware of their errors in bucco-facial and limb actions, respectively, indicating for the first time a topographical organization of the syndrome. Our approach allowed us to distinguish awareness deficits from more general disorders in error recognition; indeed, anosognosic patients were able to identify errors when the same action was executed by another patient but not when the video showed their own actions. Finally, we provide evidence that anosognosia for apraxia might be associated with frontal cortical and subcortical networks.

Visual similarity and psychological closeness are neurally dissociable in the brain response to vicarious pain.

Personal and vicarious experience of pain activate partially overlapping brain networks. This brain activity is further modulated by low- and high-order factors, e.g., the perceived intensity of the model's pain and the model's similarity with the onlooker, respectively. We investigated which specific aspect of similarity modulates such empathic reactivity, focusing on the potential differentiation between visual similarity and psychological closeness between the onlooker and different types of models. To this aim, we recorded fMRI data in neurotypical participants who observed painful and tactile stimuli delivered to an adult human hand, a baby human hand, a puppy dog paw, and an anthropomorphic robotic hand. The interaction between type of vicarious experience (pain, touch) and nature of model (adult, baby, dog, robot) showed that the right supramarginal gyrus (rSMG) was selectively active for visual similarity (more active during vicarious pain for the adult and baby models), while the anterior cingulate cortex (ACC) was more sensitive to psychological closeness (specifically linked to vicarious pain for the baby model). These findings indicate that visual similarity and psychological closeness between onlooker and model differentially affect the activity of brain regions specifically implied in encoding interindividual sharing of sensorimotor and affective aspects of vicarious pain, respectively.

Midline frontal and occipito-temporal activity during error monitoring in dyadic motor interactions.

Discrepancies between sensory predictions and action outcome are at the base of error coding. However, these phenomena have mainly been studied focussing on individual performance. Here, we explored EEG responses to motor prediction errors during a human-avatar interaction and show that Theta/Alpha activity of the frontal error-monitoring system works in phase with activity of the occipito-temporal node of the action observation network. Our motor interaction paradigm required healthy individuals to synchronize their reach-to-grasp movements with those of a virtual partner in conditions that did (Interactive) or did not require (Cued) movement prediction and adaptation to the partner's actions. Crucially, in 30% of the trials the virtual partner suddenly and unpredictably changed its movement trajectory thereby violating the human participant's expectation. These changes elicited error-related neuromarkers (ERN/Pe - Theta/Alpha modulations) over fronto-central electrodes during the Interactive condition. Source localization and connectivity analyses showed that the frontal Theta/Alpha activity induced by violations of the expected interactive movements was in phase with occipito-temporal Theta/Alpha activity. These results expand current knowledge about the neural correlates of on-line interpersonal motor interactions linking the frontal error-monitoring system to visual, body motion-related, responses.

The "embreathment" illusion highlights the role of breathing in corporeal awareness.

Recent theories posit that physiological signals contribute to corporeal awareness, the basic feeling that one has a body (body ownership) that acts according to one's will (body agency) and occupies a specific position (body location). Combining physiological recordings with immersive virtual reality, we found that an ecological mapping of real respiratory patterns onto a virtual body illusorily changes corporeal awareness. This new way of inducing a respiratory bodily illusion, called "embreathment," revealed that breathing is almost as important as visual appearance for inducing body ownership and more important than any other cue for body agency. These effects were moderated by individual levels of interoception, as assessed through a standard heartbeat-counting task and a new "pneumoception" task. By showing that respiratory, visual, and spatial signals exert a specific and weighted influence on the fundamental feeling that one is an embodied agent, we pave the way for a comprehensive hierarchical model of corporeal awareness.NEW & NOTEWORTHY Our body is the only object we sense from the inside; however, it is unclear how much inner physiology contributes to the global sensation of having a body and controlling it. We combine respiration recordings with immersive virtual reality and find that making a virtual body breathe like the real body gives an illusory sense of ownership and agency over the avatar, elucidating the role of a key physiological process like breathing in corporeal awareness.

The enfacement illusion boosts facial mimicry.

Facial mimicry, the automatic imitation of another person's emotion, is a mechanism underlying emotion recognition and emotional contagion, a phylogenetically conserved form of empathy that precedes later developing empathic skills. We tested the possibility to increase facial mimicry by blurring self-other distinction via the enfacement illusion. To do so we delivered synchronous, versus asynchronous, visuo-tactile interpersonal multisensory stimulation on the observer and expresser's faces and then recorded surface facial EMG while participants observed videos of happy and sad facial expressions displayed by the expresser. Our results show that synchronous visuo-tactile stimulation can indeed enhance facial mimicry and that this depends on participants' baseline tendency to mimic.. Our findings could set the basis for developing novel interventions for conditions characterized by reduced empathic and emotion recognition skills, including autism and schizophrenia.

Bound to the group and blinded by the leader: ideological leader-follower dynamics in a trust economic game.

Understanding the dynamics of trustworthiness in ideological contexts could influence human societies, affect electoral campaigns and ultimately impact democracy. We tested trust behaviour towards political leaders in a sample of 121 opposing/supporting voters assigned as trustors in an iterative trust game (TG). In two experiments, a famous Italian conservative leader (i.e. Silvio Berlusconi) or a famous non-politician were used as trustees in a predefined un/trustworthy TG, while trustors believed that mathematical algorithms reproduced trustee's real behaviour. Results revealed that depending on the group, voters either relied on the situation and adjusted to the behaviour of the out-group leader (in our case left-wing voters), or on their disposition for group-loyalty with respect for authority, thus failing to adjust to the behaviour of the in-group leader (in our case right-wing voters). Our findings suggest that: (i) complex voter-leader relations in politics are reflected in the simple trustor-trustee financial interactions from behavioural economics, and (ii) being bound to one's group and one's leader may affect the trust economic decisions of the followers.

Midfrontal theta transcranial alternating current stimulation modulates behavioural adjustment after error execution.

Cognitive control during conflict monitoring, error processing, and post-error adjustment appear to be associated with the occurrence of midfrontal theta (MFÏ´). While this association is supported by correlational EEG studies, much less is known about the possible causal link between MFÏ´ and error and conflict processing. In the present study, we aimed to explore the role of band-specific effects in modulating the error system during a conflict resolution. In turn, we delivered transcranial alternating current stimulation (tACS) at different frequency bands (delta δ, theta θ, alpha α, beta ß, gamma γ) and sham stimulation over the medial frontal cortex (MFC) in 36 healthy participants performing a modified version of the Flanker task. Task performance and reports about the sensations (e.g. visual flickering, cutaneous burning) induced by the different frequency bands, were also recorded. We found that online θ-tACS increased the response speed to congruent stimuli after error execution with respect to sham stimulation. Importantly, the accuracy following the errors did not decrease because of speed-accuracy trade off. Moreover, tACS evoked visual and somatosensory sensations were significantly stronger at α-tACS and ß-tACS compared to other frequencies. Our findings suggest that theta activity plays a causative role in modulating behavioural adjustments during perceptual choices in a stimulus-response conflict task.

Transitory Inhibition of the Left Anterior Intraparietal Sulcus Impairs Joint Actions: A Continuous Theta-Burst Stimulation Study.

Although temporal coordination is a hallmark of motor interactions, joint action (JA) partners do not simply synchronize; rather, they dynamically adapt to each other to achieve a joint goal. We created a novel paradigm to tease apart the processes underlying synchronization and JA and tested the causal contribution of the left anterior intraparietal sulcus (aIPS) in these behaviors. Participants had to synchronize their congruent or incongruent movements with a virtual partner in two conditions: (i) being instructed on what specific action to perform, independently from what action the partner performed (synchronization), and (ii) being instructed to adapt online to the partner's action (JA). Offline noninvasive inhibitory brain stimulation (continuous theta-burst stimulation) over the left aIPS selectively modulated interpersonal synchrony in JA by boosting synchrony during congruent interactions and impairing it during incongruent ones, while leaving performance in the synchronization condition unaffected. These results suggest that the left aIPS plays a causal role in supporting online adaptation to a partner's action goal, whereas it is not necessarily engaged in social situations where the goal of the partner is irrelevant. This indicates that, during JAs, the integration of one's own and the partner's action goal is supported by aIPS.

Theta synchronization over occipito-temporal cortices during visual perception of body parts.

Categorical clustering in the visual system is thought to have evolved as a function of intrinsic (intra-areal) and extrinsic (interareal) connectivity and experience. In the visual system, the extrastriate body area (EBA), an occipito-temporal region, responds to full body and body part images under the organizational principle of their functional/semantic meaning. Although frequency-specific modulations of neural activity associated with perceptive and cognitive functions are increasingly attracting the interest of neurophysiologists and cognitive neuroscientists, perceiving single body parts with different functional meaning and full body images induces time-frequency modulations over occipito-temporal electrodes are yet to be described. Here, we studied this issue by measuring EEG in participants who passively observed fingers, hands, arms and faceless full body images with four control plant stimuli, each bearing hierarchical analogy with the body stimuli. We confirmed that occipito-temporal electrodes (compatible with the location of EBA) show a larger event-related potential (ERP, N190) for body-related images. Furthermore, we identified a body part-specific (i.e. selective for hands and arms) theta event-related synchronization increase under the same electrodes. This frequency modulation associated with the perception of body effectors over occipito-temporal cortices is in line with recent findings of categorical organization of neural responses to human effectors in the visual system.

Come together: human-avatar on-line interactions boost joint-action performance in apraxic patients.

Limb apraxia (LA) is a high-order motor disorder linked to left-hemisphere damage. It is characterized by defective execution of purposeful actions upon delayed imitation, or verbal command when the actions are performed in isolated, non-naturalistic, conditions. Whether interpersonal interactions provide social affordances that activate neural resources different from those requested by individual action execution, which may improve LA performance, is unknown. To fill this gap, we measured interaction performance, behavioral and kinematic indexes of left-brain damaged patients with/without LA in a social reach-to-grasp task involving two different degrees of spatio-temporal interactivity with an avatar. We found that LA patients' impairment in coordinating with the virtual partner was abolished in highly interactive conditions (where patients selected their actions on-line based on the behavior of the virtual partner) with respect to low interactive conditions (where actions were selected beforehand based on abstract instructions). Voxel-based-Lesion-Symptom-Mapping indicated that impairments in low-interactive conditions were underpinned by lesions of premotor, motor and insular areas, and of the basal ganglia. Our approach expands current understanding of the behavioral and neural correlates of interactive motor performance by highlighting the important role of social affordances, and provides novel, potentially important, views on rehabilitation of higher-order motor cognition disorders.

Catching on it early: Bodily and brain anticipatory mechanisms for excellence in sport.

Programming and executing a subsequent move is inherently linked to the ability to anticipate the actions of others when interacting. Such fundamental social ability is particularly important in sport. Here, we discuss the possible mechanisms behind the highly sophisticated anticipation skills that characterize experts. We contend that prediction in sports might rely on a finely tuned perceptual system that endows experts with a fast, partially unconscious, pickup of relevant cues. Furthermore, we discuss the role of the multimodal, perceptuomotor, multiple-duty cells (mirror neurons) that play an important function in action anticipation by means of an inner motor simulation process. Finally, we suggest the role of predictive coding, interoception, and the enteric nervous system as the processual and biological support for intuition and "gut feelings" in sports-the missing link that might explain outstanding expert performance based on action anticipation.

Visual appearance of a virtual upper limb modulates the temperature of the real hand: a thermal imaging study in Immersive Virtual Reality.

To explore the link between Sense of Embodiment (SoE) over a virtual hand and physiological regulation of skin temperature, 24 healthy participants were immersed in virtual reality through a Head Mounted Display and had their real limb temperature recorded by means of a high-sensitivity infrared camera. Participants observed a virtual right upper limb (appearing either normally, or with the hand detached from the forearm) or limb-shaped non-corporeal control objects (continuous or discontinuous wooden blocks) from a first-person perspective. Subjective ratings of SoE were collected in each observation condition, as well as temperatures of the right and left hand, wrist and forearm. The observation of these complex, body and body-related virtual scenes resulted in increased real hand temperature when compared to a baseline condition in which a 3d virtual ball was presented. Crucially, observation of non-natural appearances of the virtual limb (discontinuous limb) and limb-shaped non-corporeal objects elicited high increase in real hand temperature and low SoE. In contrast, observation of the full virtual limb caused high SoE and low temperature changes in the real hand with respect to the other conditions. Interestingly, the temperature difference across the different conditions occurred according to a topographic rule that included both hands. Our study sheds new light on the role of an external hand's visual appearance and suggests a tight link between higher-order bodily self-representations and topographic regulation of skin temperature.

The Role of Audio-Visual Feedback in a Thought-Based Control of a Humanoid Robot: A BCI Study in Healthy and Spinal Cord Injured People.

The efficient control of our body and successful interaction with the environment are possible through the integration of multisensory information. Brain-computer interface (BCI) may allow people with sensorimotor disorders to actively interact in the world. In this study, visual information was paired with auditory feedback to improve the BCI control of a humanoid surrogate. Healthy and spinal cord injured (SCI) people were asked to embody a humanoid robot and complete a pick-and-place task by means of a visual evoked potentials BCI system. Participants observed the remote environment from the robot's perspective through a head mounted display. Human-footsteps and computer-beep sounds were used as synchronous/asynchronous auditory feedback. Healthy participants achieved better placing accuracy when listening to human footstep sounds relative to a computer-generated sound. SCI people demonstrated more difficulty in steering the robot during asynchronous auditory feedback conditions. Importantly, subjective reports highlighted that the BCI mask overlaying the display did not limit the observation of the scenario and the feeling of being in control of the robot. Overall, the data seem to suggest that sensorimotor-related information may improve the control of external devices. Further studies are required to understand how the contribution of residual sensory channels could improve the reliability of BCI systems.

Motor imagery in spinal cord injured people is modulated by somatotopic coding, perspective taking, and post-lesional chronic pain.

Motor imagery (MI) allows one to mentally represent an action without necessarily performing it. Importantly, however, MI is profoundly influenced by the ability to actually execute actions, as demonstrated by the impairment of this ability as a consequence of lesions in motor cortices, limb amputations, movement limiting chronic pain, and spinal cord injury. Understanding MI and its deficits in patients with motor limitations is fundamentally important as development of some brain-computer interfaces and daily life strategies for coping with motor disorders are based on this ability. We explored MI in a large sample of patients with spinal cord injury (SCI) using a comprehensive battery of questionnaires to assess the ability to imagine actions from a first-person or a third-person perspective and also imagine the proprioceptive components of actions. Moreover, we correlated MI skills with personality measures and clinical variables such as the level and completeness of the lesion and the presence of chronic pain. We found that the MI deficits (1) concerned the body parts affected by deafferentation and deefferentation, (2) were present in first- but not in third-person perspectives, and (3) were more altered in the presence of chronic pain. MI is thus closely related to bodily perceptions and representations. Every attempt to devise tools and trainings aimed at improving autonomy needs to consider the cognitive changes due to the body-brain disconnection.

Interactions Between Body and Social Awareness in Yoga.

BACKGROUND/OBJECTIVE: Bodily processes have been intimately linked to social-cognitive and affective functions, such as compassion and empathy. Yet, little is known about how awareness of bodily processes influences social awareness and vice versa, especially in nonobservational but experiential investigations. This study investigated the relationship between psychometrically reported body and social awareness (including altruism, empathy, perspective-taking, and compassion) in 90 yoga and yoga-/mediation-naive control participants. In modern postural yoga, advanced practitioners claim both increased compassion and inner focus. METHODS: Multiple regression analyses were conducted to predict (1) the level of yoga practice from body awareness and social awareness skills in the yoga group and (2) body awareness from social skills in both groups. RESULTS: Body awareness and compassion were significant positive and independent predictors of yoga expertise. This finding supports practitioners' anecdotal claims but also implies that both functions tap into different aspects of yoga expertise. When body awareness was predicted, altruism emerged as a significant negative predictor in the yoga group (but not control group) as a function of yoga practice. CONCLUSION: These results might compellingly suggest that, despite high compassion, heightened bodily self-awareness might increase a self-centred perspective and limit altruistic acts in advanced yoga practitioners.

Thermal signatures of voluntary deception in ecological conditions.

Deception is a pervasive phenomenon that greatly influences dyadic, groupal and societal interactions. Behavioural, physiological and neural signatures of this phenomenon have imporant implications for theoretical and applied research, but, because it is difficult for a laboratory to replicate the natural context in which deception occurs, contemporary research is still struggling to find such signatures. In this study, we tracked the facial temperature of participants who decided whether or not to deceive another person, in situations where their reputation was at risk or not. We used a high-sensitivity infrared device to track temperature changes to check for unique patterns of autonomic reactivity. Using a region-of-interest based approach we found that prior to any response there was a minimal increase in periorbital temperature (which indexes sympathetic activation, together with reduced cheek temperature) for the self-gain lies in the reputation-risk condition. Crucially, we found a rise in nose temperature (which indexes parasympathetic activation) for self-gain lies in the reputation-risk condition, not only during response preparation but also after the choice was made. This finding suggests that the entire deception process may be tracked by the nose region. Furthermore, this nasal temperature modulation was negatively correlated with machiavellian traits, indicating that sympathetic/parasympathetic regulation is less important for manipulative individuals who may care less about the consequences of lie-related moral violations. Our results highlight a unique pattern of autonomic reactivity for spontaneous deception in ecological contexts.

Social cues to joint actions: the role of shared goals.

In daily life, we do not just move independently from how others move. Rather, the way we move conveys information about our cognitive and affective attitudes toward our conspecifics. However, the implicit social substrate of our movements is not easy to capture and isolate given the complexity of human interactive behaviors. In this perspective article we discuss the crucial conditions for exploring the impact of "interpersonal" cognitive/emotional dimensions on the motor behavior of individuals interacting in realistic contexts. We argue that testing interactions requires one to build up naturalistic and yet controlled scenarios where participants reciprocally adapt their movements in order to achieve an overarching "shared goal." We suggest that a shared goal is what singles out real interactions from situations where two or more individuals contingently but independently act next to each other, and that "interpersonal" socio-emotional dimensions might fail to affect co-agents' behaviors if real interactions are not at place. We report the results of a novel joint-grasping task suitable for exploring how individual sub-goals (i.e., correctly grasping an object) relate to, and depend from, the representation of "shared goals."

Causative role of left aIPS in coding shared goals during human-avatar complementary joint actions.

Successful motor interactions require agents to anticipate what a partner is doing in order to predictively adjust their own movements. Although the neural underpinnings of the ability to predict others' action goals have been well explored during passive action observation, no study has yet clarified any critical neural substrate supporting interpersonal coordination during active, non-imitative (complementary) interactions. Here, we combine non-invasive inhibitory brain stimulation (continuous Theta Burst Stimulation) with a novel human-avatar interaction task to investigate a causal role for higher-order motor cortical regions in supporting the ability to predict and adapt to others' actions. We demonstrate that inhibition of left anterior intraparietal sulcus (aIPS), but not ventral premotor cortex, selectively impaired individuals' performance during complementary interactions. Thus, in addition to coding observed and executed action goals, aIPS is crucial in coding 'shared goals', that is, integrating predictions about one's and others' complementary actions.

Virtual lesion of right posterior superior temporal sulcus modulates conscious visual perception of fearful expressions in faces and bodies.

The posterior Superior Temporal Suclus (pSTS) represents a central hub in the complex cerebral network for person perception and emotion recognition as also suggested by its heavy connections with face- and body-specific cortical (e.g., the fusiform face area, FFA and the extrastriate body area, EBA) and subcortical structures (e.g., amygdala). Information on whether pSTS is causatively involved in sustaining conscious visual perception of emotions expressed by faces and bodies is lacking. We explored this issue by combining a binocular rivalry procedure (where emotional and neutral face and body postures rivaled with house images) with off-line, 1-Hz repetitive transcranial magnetic stimulation (rTMS). We found that temporary inhibition of the right pSTS reduced perceptual dominance of fearful faces and increased perceptual dominance of fearful bodies, while leaving unaffected the perception of neutral face and body images. Inhibition of the vertex had no effect on conscious visual perception of neutral or emotional face or body stimuli. Thus, the right pSTS plays a causal role in shortening conscious vision of fearful faces and in prolonging conscious vision of fearful bodies. These results suggest that pSTS selectively modulates the activity of segregated networks involved in the conscious visual perception of emotional faces or bodies. We speculate that the opposite role of the right pSTS for conscious perception of fearful face and body may be explained by the different connections that this region entertains with face- and body-selective visual areas as well as with amygdalae and premotor regions.