Building the bodily self-awareness: Evidence for the convergence between interoceptive and exteroceptive information in a multilevel kernel density analysis study

Heartbeat-evoked potentials following voluntary hyperventilation in epilepsy patients: respiratory influences on cardiac interoception

Introduction

Current evidence indicates a modulating role of respiratory processes in cardiac interoception, yet whether altered breathing patterns influence heartbeat-evoked potentials (HEP) remains inconclusive.

Methods

Here, we examined the effects of voluntary hyperventilation (VH) as part of a clinical routine examination on scalp-recorded HEPs in epilepsy patients (N = 80).

Results

Using cluster-based permutation analyses, HEP amplitudes were compared across pre-VH and post-VH conditions within young and elderly subgroups, as well as for the total sample. No differences in the HEP were detected for younger participants or across the full sample, while an increased late HEP during pre-VH compared to post-VH was fond in the senior group, denoting decreased cardiac interoceptive processing after hyperventilation.

Discussion

The present study, thus, provides initial evidence of breathing-related HEP modulations in elderly epilepsy patients, emphasizing the potential of HEP as an interoceptive neural marker that could partially extend to the representation of pulmonary signaling. We speculate that aberrant CO2-chemosensing, coupled with disturbances in autonomic regulation, might constitute the underlying pathophysiological mechanism behind the obtained effect. Available databases involving patient records of routine VH assessment may constitute a valuable asset in disentangling the interplay of cardiac and ventilatory interoceptive information in various patient groups, providing thorough clinical data to parse, as well as increased statistical power and estimates of effects with higher precision through large-scale studies.

Schizophrenia and the bodily self

Despite the historically consolidated psychopathological perspective, on the one hand, contemporary organicistic psychiatry often highlights abnormalities in neurotransmitter systems like dysregulation of dopamine transmission, neural circuitry, and genetic factors as key contributors to schizophrenia. Neuroscience, on the other, has so far almost entirely neglected the first-person experiential dimension of this syndrome, mainly focusing on high-order cognitive functions, such as executive function, working memory, theory of mind, and the like. An alternative view posits that schizophrenia is a self-disorder characterized by anomalous self-experience and awareness. This view may not only shed new light on the psychopathological features of psychosis but also inspire empirical research targeting the bodily and neurobiological changes underpinning this disorder. Cognitive neuroscience can today address classic topics of phenomenological psychopathology by adding a new level of description, finally enabling the correlation between the first-person experiential aspects of psychiatric diseases and their neurobiological roots. Recent empirical evidence on the neurobiological basis of a minimal notion of the self, the bodily self, is presented. The relationship between the body, its motor potentialities and the notion of minimal self is illustrated. Evidence on the neural mechanisms underpinning the bodily self, its plasticity, and the blurring of self-other distinction in schizophrenic patients is introduced and discussed. It is concluded that brain-body function anomalies of multisensory integration, differential processing of self- and other-related bodily information mediating self-experience, might be at the basis of the disruption of the self disorders characterizing schizophrenia.

Cardiac interoception in Anorexia Nervosa: A resting-state heartbeat-evoked potential study

OBJECTIVE

A deficit in interoception - the ability to perceive, interpret and integrate afferent signals about the physiological state of the body - has been shown in Anorexia Nervosa (AN), and linked to altered hunger sensations, body dysmorphia, and abnormal emotional awareness. The present high-density electroencephalography (hdEEG) study aims to assess cardiac interoception in AN and to investigate its neural correlates, using an objective neurophysiological measure.

METHOD

Heartbeat-evoked potentials (HEPs) were computed from 5 min of resting-state EEG and electrocardiogram (ECG) data and compared between individuals with AN (N = 22) and healthy controls (HC) (N = 19) with waveform, topographic, and source imaging analyses.

RESULTS

Differences in the cortical representation of heartbeats were present between AN and HC at a time window of 332-348 ms after the ECG R-peak. Source imaging analyses revealed a right-sided hypoactivation in AN of brain regions linked to interoceptive processing, such as the anterior cingulate and orbitofrontal areas.

CONCLUSIONS

To the best of our knowledge, this is the first study using hdEEG to localise the underlying sources of HEPs in AN. Results point to altered interoceptive processing during resting-state in AN. As our participants had a short duration of illness, this might not be the consequence of prolonged starvation. Interventions targeted at interoception could provide an additional tool to facilitate recovery.

The Neurophysiology of Interoceptive Disruptions in Trauma-Exposed Populations

In the aftermath of psychological trauma, many individuals experience perturbations in interoception, a term that broadly references the ability to accurately detect body signals and integrate these signals with emotional states. These interoceptive disruptions can manifest in different ways, including blunting or amplification of sensitivity to internal physiological signals. In this chapter we review extant neurophysiological research on interoception in trauma-exposed populations, with a particular focus on the effects of chronic interpersonal trauma, such as childhood maltreatment and racial discrimination. We explore research that used different types of interoceptive assays, from self-report measures to electrophysiological and neuroimaging tools to characterize the disruptions in pain perception, interoceptive acuity, and physiological responses that may arise after a traumatic event. Finally, we discuss interventions that are designed to target interoceptive mechanisms, from exposure-based therapies to mindfulness-based practices, as well as future directions in trauma interoception research.

Shared and distinctive neural substrates of generalized anxiety disorder with or without depressive symptoms and their roles in prognostic prediction

BACKGROUND

The neurophysiological mechanisms underlying generalized anxiety disorder (GAD) with or without depressive symptoms are obscure. This study aimed to uncover them and assess their predictive value for treatment response.

METHODS

We enrolled 98 GAD patients [58 (age: 33.22 ± 10.23 years old, males/females: 25/33) with and 40 (age: 33.65 ± 10.49 years old, males/females: 14/26) without depressive symptoms] and 54 healthy controls (HCs, age: 32.28 ± 10.56 years old, males/females: 21/33). Patients underwent clinical assessments and resting-state functional MRI (rs-fMRI) at baseline and after 4-week treatment with paroxetine, while HCs underwent rs-fMRI at baseline only. Regional homogeneity (ReHo) was employed to measure intrinsic brain activity. We compared ReHo in patients to HCs and examined changes in ReHo within the patient groups after treatment. Support vector regression (SVR) analyses were conducted separately for each patient group to predict the patients' treatment response.

RESULTS

Both patient groups exhibited higher ReHo in the middle/superior frontal gyrus decreased ReHo in different brain regions compared to HCs. Furthermore, differences in ReHo were detected between the two patient groups. After treatment, the patient groups displayed distinct ReHo change patterns. By utilizing SVR based on baseline abnormal ReHo, we effectively predicted treatment response of patients (p-value for correlation < 0.05).

LIMITATIONS

The dropout rate was relatively high.

CONCLUSIONS

This study identified shared and unique neural substrates in GAD patients with or without depressive symptoms, potentially serving as biomarkers for treatment response prediction. Comorbid depressive symptoms were associated with differences in disease manifestation and treatment response compared to pure GAD cases.

Subcortical contributions to the sense of body ownership

The sense of body ownership (i.e. the feeling that our body or its parts belong to us) plays a key role in bodily self-consciousness and is believed to stem from multisensory integration. Experimental paradigms such as the rubber hand illusion have been developed to allow the controlled manipulation of body ownership in laboratory settings, providing effective tools for investigating malleability in the sense of body ownership and the boundaries that distinguish self from other. Neuroimaging studies of body ownership converge on the involvement of several cortical regions, including the premotor cortex and posterior parietal cortex. However, relatively less attention has been paid to subcortical structures that may also contribute to body ownership perception, such as the cerebellum and putamen. Here, on the basis of neuroimaging and neuropsychological observations, we provide an overview of relevant subcortical regions and consider their potential role in generating and maintaining a sense of ownership over the body. We also suggest novel avenues for future research targeting the role of subcortical regions in making sense of the body as our own.

The Body in Neurosciences: Representation, Perception and Space Processing

The Special Issue "The Body in Neurosciences: Representation, Perception and Space Processing" deals with the understanding of body processing in terms of the multisensorial perception of bodily related information, interoception, and mental representation, as well as its relationship with the peripersonal, interpersonal, and extrapersonal spaces, integrating findings from normal and pathological functioning [...].

Me, Myself, and I: Neural Activity for Self versus Other across Development

Although adults and children differ in self-vs.-other perception, a developmental perspective on this discriminative ability at the brain level is missing. This study examined neural activation for self-vs.-other in a sample of 39 participants spanning four different age groups, from 4-year-olds to adults. Self-related stimuli elicited higher neural activity within two brain regions related to self-referential thinking, empathy, and social cognition processes. Second, stimuli related to 'others' (i.e., unknown peer) elicited activation within nine additional brain regions. These regions are associated with multisensory processing, somatosensory skills, language, complex visual stimuli, self-awareness, empathy, theory of mind, and social recognition. Overall, activation maps were gradually increasing with age. However, patterns of activity were non-linear within the medial cingulate cortex for 'self' stimuli and within the left middle temporal gyrus for 'other' stimuli in 7-10-year-old participants. In both cases, there were no self-vs.-other differences. It suggests a critical period where the perception of self and others are similarly processed. Furthermore, 11-19-year-old participants showed no differences between others and self within the left inferior orbital gyrus, suggesting less distinction between self and others in social learning. Understanding the neural bases of self-vs.-other discrimination during development can offer valuable insights into how social contexts can influence learning processes during development, such as when to introduce peer-to-peer teaching or group learning.

Neurophysiological changes associated with vibroacoustically-augmented breath-focused mindfulness for dissociation: targeting interoception and attention

BACKGROUND

Dissociative symptoms can emerge after trauma and interfere with attentional control and interoception; disruptions to these processes are barriers to mind-body interventions such as breath-focused mindfulness (BFM). To overcome these barriers, we tested the use of an exteroceptive augmentation to BFM, using vibrations equivalent to the amplitude of the auditory waveform of the actual breath, delivered via a wearable subwoofer in real time (VBFM). We tested whether this device enhanced interoceptive processes, attentional control and autonomic regulation in trauma-exposed women with dissociative symptoms.

METHODS

65 women, majority (82%) Black American, aged 18-65 completed self-report measures of interoception and 6 BFM sessions, during which electrocardiographic recordings were taken to derive high-frequency heart rate variability (HRV) estimates. A subset (n = 31) of participants completed functional MRI at pre- and post-intervention, during which they were administered an affective attentional control task.

RESULTS

Compared to those who received BFM only, women who received VBFM demonstrated greater increases in interoception, particularly their ability to trust body signals, increased sustained attention, as well as increased connectivity between nodes of emotion processing and interoceptive networks. Intervention condition moderated the relationship between interoception change and dissociation change, as well as the relationship between dissociation and HRV change.

CONCLUSIONS

Vibration feedback during breath focus yielded greater improvements in interoception, sustained attention and increased connectivity of emotion processing and interoceptive networks. Augmenting BFM with vibration appears to have considerable effects on interoception, attention and autonomic regulation; it could be used as a monotherapy or to address trauma treatment barriers.

Self-touch facilitates the recognition of the dis-owned left hand in somatoparaphrenia: a single case study

We investigated whether self-administered tactile stimulation could act as a temporary restorative mechanism for body ownership disorders, both implicitly and explicitly. We tested this hypothesis in a patient with somatoparaphrenia, who displayed increased accuracy in explicitly recognizing their left hand during self-touch. Furthermore, the patient implicitly perceived their hand and the experimenter's hand as more belonging to their own body compared to conditions where vision was the sole sensory input. These findings highlight the importance of self-touch in maintaining a coherent body representation, while also demonstrating the potential dissociation between the recovery of explicit and implicit perceptions of body ownership.

Disentangling the Neural Correlates of Agency, Ownership and Multisensory Processing

The experience of the self as an embodied agent in the world is an essential aspect of human consciousness. This experience arises from the feeling of control over one's bodily actions, termed the Sense of Agency, and the feeling that the body belongs to the self, Body Ownership. Despite long-standing philosophical and scientific interest in the relationship between the body and brain, the neural systems involved in Body Ownership and Sense of Agency, and especially their interactions, are not yet understood. In this preregistered study using the Moving Rubber Hand Illusion inside an MR-scanner, we aimed to uncover the relationship between Body Ownership and Sense of Agency in the human brain. Importantly, by using both visuomotor and visuotactile stimulations and measuring online trial-by-trial fluctuations in the illusion magnitude, we were able to disentangle brain systems related to objective sensory stimulation and subjective judgments of the bodily-self. Our results indicate that at both the behavioral and neural levels, Body Ownership and Sense of Agency are strongly interrelated. Multisensory regions in the occipital and fronto-parietal regions encoded convergence of sensory stimulation conditions. The subjective judgments of the bodily-self were related to BOLD fluctuations in the Somatosensory cortex and in regions not activated by the sensory conditions, such as the insular cortex and precuneus. Our results highlight the convergence of multisensory processing in specific neural systems for both Body Ownership and Sense of Agency with partially dissociable regions for subjective judgments in regions of the Default Mode Network.

Combining the Inner Self with the Map of the Body: Evidence for White Matter Contribution to the Relation Between Interoceptive Sensibility and Nonaction-oriented Body Representation

Very recent studies on healthy individuals suggest that changes in the sensibility toward internal bodily sensations across the lifespan affect the ability to mentally represent one's body, in terms of action-oriented and nonaction-oriented body representation (BR). Little is known about the neural correlates of this relation. Here we fill this gap using the neuropsychological model provided by focal brain damage. Sixty-five patients with unilateral stroke (20 with left and 45 with right brain damage, LBD and RBD, respectively) participated in this study. Both action-oriented BR and nonaction-oriented BR were tested; interoceptive sensibility was assessed as well. First, we tested whether interoceptive sensibility predicted action-oriented BR and nonaction-oriented BR, in RBD and LBD separately. Then, a track-wise hodological lesion-deficit analysis was performed in a subsample of twenty-four patients to test the brain network supporting this relation. We found that interoceptive sensibility predicted the performances in the task tapping nonaction-oriented BR. The higher interoceptive sensibility was, the worse patients performed. This relation was associated with the disconnection probability of the corticospinal tract, the fronto-insular tract, and the pons. We expand over the previous findings on healthy individuals, supporting the idea that high levels of interoceptive sensibility negatively affect BR. Specific frontal projections and frontal u-shaped tracts may play a pivotal role in such an effect, likely affecting the development of a first-order representation of the self within the brainstem autoregulatory centers and posterior insula and of a second-order representation of the self within the anterior insula and higher-order prefrontal areas.

Relating different Dimensions of Bodily Experiences: Review and proposition of an integrative model relying on phenomenology, predictive brain and neuroscience of the self

How we mentally experience our body has been studied in a variety research domains. Each of these domains focuses in its own ways on different aspects of the body, namely the neurophysiological, perceptual, affective or social components, and proposes different conceptual taxonomies. It is therefore difficult to find one's way through this vast literature and to grasp the relationships between the different dimensions of bodily experiences. In this narrative review, we summarize the existing research directions and present their limits. We propose an integrative framework, grounded in studies on phenomenal consciousness, self-consciousness and bodily self-consciousness, that can provide a common basis for evaluating findings on different dimensions of bodily experiences. We review the putative mechanisms, relying on predictive processes, and neural substrates that support this model. We discuss how this model enables a conceptual assessment of the interrelationships between multiple dimensions of bodily experiences and potentiate interdisciplinary approaches.

Neural substrates of interoceptive sensibility: An integrated study in normal and pathological functioning

In early studies interoception strictly referred to the awareness of visceral sensations, but recent theories have expanded this concept to denote the ongoing status of the body, including somatosensory feelings. Here, we integrated data from normal and pathological functioning to disclose neural underpinnings of interoceptive sensibility, taking into account the crucial distinction between visceral and somatosensory feelings. Twenty-seven healthy young individuals underwent structural MRI (including T1w images and DTI). Voxel-wise analyses of the gyrification index (GI) and fractional anisotropy (FA) data were performed to assess the relation between interoceptive sensibility and surface morphometry and anatomical connectivity. Thirty-three unilateral brain-damaged patients took part in this study for Voxel-Based Lesion-Symptom Mapping (VLSM) and track-wise hodological lesion-deficit analysis (TWH). All participants completed the Self-Awareness Questionnaire (SAQ), a self-report tool assessing interoceptive sensibility of visceral (F1) and somatosensory feelings (F2). Tract-Based Spatial Statistics showed that F2 was positively associated with FA in the bilateral anterior thalamic radiation, corticospinal tract, cingulum, forceps, inferior longitudinal, fronto-occipital, superior longitudinal, and uncinate fasciculi; no significant association was detected for F1. However, F1 was positively associated with GI in the left anterior cingulate cortex. VLSM showed that F1 mainly relies on the right posterior insula, whereas F2 is related mostly to subcortical nuclei and surrounding white matter in the right hemisphere. Accordingly, patients with disconnection of the anterior thalamic projection, corticospinal tract, inferior fronto-occipital, inferior longitudinal, uncinate and superior longitudinal fasciculus III showed lower scores on F2. Overall, results support the dissociation between interoceptive sensibility of visceral and somatosensory feelings.

The Role of the Skin in Interoception: A Neglected Organ?

In the past 2 decades, interoception has received increasing attention in the fields of psychology and cognitive science, as well as neuroscience and physiology. A plethora of studies adopted the perception of cardiac signals as a proxy for interoception. However, recent findings have cast doubt on the methodological and intrinsic validity of the tasks used thus far. Therefore, there is an ongoing effort to improve the existing cardiac interoceptive tasks and to identify novel channels to target the perception of the physiological state of the body. Amid such scientific abundancy, one could question whether the field has been partially neglecting one of our widest organs in terms of dimensions and functions: the skin. According to some views grounded on anatomical and physiological evidence, skin-mediated signals such as affective touch, pain, and temperature have been redefined as interoceptive. However, there is no agreement in this regard. Here, we discuss some of the anatomical, physiological, and experimental arguments supporting the scientific study of interoception by means of skin-mediated signals. We argue that more attention should be paid to the skin as a sensory organ that monitors the bodily physiological state and further propose thermosensation as a particularly attractive model of skin-mediated interoception.

The neuroscience of body memory: Recent findings and conceptual advances

The body is a very special object, as it corresponds to the physical component of the self and it is the medium through which we interact with the world. Our body awareness includes the mental representation of the body that happens to be our own, and traditionally has been defined in terms of body schema and body image. Starting from the distinction between these two types of representations, the present paper tries to reconcile the literature around body representations under the common framework of body memory. The body memory develops ontogenetically from birth and across all the life span and is directly linked to the development of the self. Therefore, our sense of self and identity is fundamentally based on multisensory knowledge accumulated in body memory, so that the sensations collected by our body, stored as implicit memory, can unfold in the future, under suitable circumstances. Indeed, these sets of bodily information had been proposed as possible key factors underpinning several mental health illnesses. Following this perspective, the Embodied Medicine approach put forward the use of advanced technologies to alter the dysfunctional body memory to enhance people's well-being. In the last sections, recent experimental pieces of evidence will be illustrated that targeted specifically bodily information for increasing health and wellbeing, by means of two strategies: interoceptive feedback and bodily illusions. See also Figure 1(Fig. 1).

Sense of self in mind and body: an eLORETA-EEG study

The human brain engages the sense of self through both semantic and somatic self-referential processing (SRP). Alpha and theta oscillations have been found to underlie SRP but have not been compared with respect to semantic and somatic SRP. We recorded electroencephalography (EEG) from 50 participants during focused internal attention on life roles (e.g. "friend") and outer body (e.g. "arms") compared to resting state and an external attention memory task and localized the sources of on-scalp alpha (8-12 Hz) and theta (4-8 Hz) EEG signals with exact low-resolution tomography. Logarithm of F-ratios was calculated to compare differences in alpha and theta power between SRP conditions, resting state, and external attention. Results indicated that compared to resting state, semantic SRP induced lower theta in the frontal cortex and higher theta in the parietal cortex, whereas somatic SRP induced lower alpha in the frontal and insula cortex and higher alpha in the parietal cortex. Furthermore, results indicated that compared to external attention, both semantic and somatic SRP induced higher alpha in the dorsolateral prefrontal cortex with lateralized patterns based on task condition. Finally, an analysis directly comparing semantic and somatic SRP indicated frontal-parietal and left-right lateralization of SRP in the brain. Our results suggest the alpha and theta oscillations in the frontal, parietal, and the insula cortex may play crucial roles in semantic and somatic SRP.

Modeling affective touch pleasantness across skin types at the individual level reveals a reliable and stable basic function

Touch is perceived most pleasant when delivered at velocities known to optimally activate the C-tactile afferent system. At the group level, pleasantness ratings of touch delivered at velocities in the range between 0.3 and 30 cm/s follow an inverted-U shape curve, with maximum pleasantness between 1 and 10 cm/s. However, the prevalence, reliability, and stability of this function at the individual level and across skin types based on hair density remains unknown. Here, we tested a range of seven velocities (0.3, 1, 3, 6, 9, 18, and 27 cm/s) delivered with a soft brush, on both hairy (forearm and dorsal hand) and nonhairy skin (palm) in 123 participants. Our results suggest that the relationship between pleasantness and velocity of touch is significantly best described by a negative quadratic model at the individual level in the majority of participants both on hairy (67.1%) and nonhairy (62.6%) skin, a larger extent than previously reported. Higher interoceptive accuracy and self-reported depression were related to a better fit of the quadratic model and the steepness of the curve, respectively. The prevalence of the quadratic model at the individual level was stable across body sites (62.6%, experiment 1), across two experimental sessions (73%-78%, experiment 2), and regardless of the number of repetitions of each velocity (experiment 3). Thus, the individual perception of tactile pleasantness follows a characteristic velocity-dependent function across skin types and shows trait characteristics. Future studies can investigate further the possibility to use affective touch as a behavioral biomarker for mental health disorders.NEW & NOTEWORTHY Touch is perceived as most pleasant when delivered at slow, caress-like velocities, known to activate C-tactile afferents. At the group level, tactile pleasantness and velocity of touch show a reliable pattern of relationship on hairy skin. Here, we found that the perception of tactile pleasantness follows a consistent pattern also at the individual level, across skin types and testing sessions. However, individual differences in interoceptive abilities and self-reported depression do play a role.

Melanocortin 4 receptor agonism enhances sexual brain processing in women with hypoactive sexual desire disorder

BACKGROUND

Hypoactive sexual desire disorder (HSDD) is characterized by a persistent deficiency of sexual fantasies and desire for sexual activity, causing marked distress and interpersonal difficulty. It is the most prevalent female sexual health problem globally, affecting approximately 10% of women, but has limited treatment options. Melanocortin 4 receptor (MC4R) agonists have emerged as a promising therapy for women with HSDD, through unknown mechanisms. Studying the pathways involved is crucial for our understanding of normal and abnormal sexual behavior.

METHODS

Using psychometric, functional neuroimaging, and hormonal analyses, we conducted a randomized, double-blinded, placebo-controlled, crossover clinical study to assess the effects of MC4R agonism compared with placebo on sexual brain processing in 31 premenopausal heterosexual women with HSDD.

RESULTS

MC4R agonism significantly increased sexual desire for up to 24 hours after administration compared with placebo. During functional neuroimaging, MC4R agonism enhanced cerebellar and supplementary motor area activity and deactivated the secondary somatosensory cortex, specifically in response to visual erotic stimuli, compared with placebo. In addition, MC4R agonism enhanced functional connectivity between the amygdala and the insula during visual erotic stimuli compared with placebo.

CONCLUSION

These data suggest that MC4R agonism enhanced sexual brain processing by reducing self-consciousness, increasing sexual imagery, and sensitizing women with HSDD to erotic stimuli. These findings provide mechanistic insight into the action of MC4R agonism in sexual behavior and are relevant to the ongoing development of HSDD therapies and MC4R agonist development more widely.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04179734.

FUNDING

This is an investigator-sponsored study funded by AMAG Pharmaceuticals Inc., the Medical Research Council (MRC) (MR/T006242/1), and the National Institute for Health Research (NIHR) (CS-2018-18-ST2-002 and RP-2014-05-001).

Investigation of Brain Activation Patterns Related to the Feminization or Masculinization of Body and Face Images across Genders

Previous studies demonstrated sex-related differences in several areas of the human brain, including patterns of brain activation in males and females when observing their own bodies and faces (versus other bodies/faces or morphed versions of themselves), but a complex paradigm touching multiple aspects of embodied self-identity is still lacking. We enrolled 24 healthy individuals (12 M, 12 F) in 3 different fMRI experiments: the vision of prototypical body silhouettes, the vision of static images of the face of the participants morphed with prototypical male and female faces, the vision of short videos showing the dynamic transformation of the morphing. We found differential sexual activations in areas linked to self-identity and to the ability to attribute mental states: In Experiment 1, the male group activated more the bilateral thalamus when looking at sex congruent body images, while the female group activated more the middle and inferior temporal gyrus. In Experiment 2, the male group activated more the supplementary motor area when looking at their faces; the female group activated more the dorsomedial prefrontal cortex (dmPFC). In Experiment 3, the female group activated more the dmPFC when observing either the feminization or the masculinization of their face. The defeminization produced more activations in females in the left superior parietal lobule and middle occipital gyrus. The performance of all classifiers built using single ROIs exceeded chance level, reaching an area under the ROC curves > 0.85 in some cases (notably, for Experiment 2 using the V1 ROI). The results of the fMRI tasks showed good agreement with previously published studies, even if our sample size was small. Therefore, our functional MRI protocol showed significantly different patterns of activation in males and females, but further research is needed both to investigate the gender-related differences in activation when observing a morphing of their face/body, and to validate our paradigm using a larger sample.

Self-Reported Body Awareness: Validation of the Postural Awareness Scale and the Multidimensional Assessment of Interoceptive Awareness (Version 2) in a Non-clinical Adult French-Speaking Sample

Body awareness refers to the individual ability to process signals originating from within the body, which provide a mapping of the body’s internal landscape (interoception) and its relation with space and movement (proprioception). The present study aims to evaluate psychometric properties and validate in French two self-report measures of body awareness: the Postural Awareness Scale (PAS), and the last version of the Multidimensional Assessment of Interoceptive Awareness questionnaire (version 2, MAIA-2). We collected data in a non-clinical, adult sample (N = 308; 61% women, mean age 35 ± 12 years) using online survey, and a subset of the original sample (n = 122; 62% women, mean age 44 ± 11 years) also completed the retest control. Factor analyses and reliability analyses were conducted. Construct validity of the PAS and the MAIA-2 were examined by testing their association with each other, and with self-report measures of personality (Big Five Inventory), alexithymia (Toronto Alexithymia Scale) and dispositional trait mindfulness (Freiburg Mindfulness Inventory). Factor analyses of the PAS supported the same two-factor structure as previously published versions (in other languages). For the MAIA-2, factor analyses suggested that a six-factor structure, excluding Not-Worrying and Not-Distracting factors, could successfully account for a common general factor of self-reported interoception. We found satisfactory internal consistency, construct validity, and reliability over time for both the PAS and the MAIA-2. Altogether, our findings suggest that the French version of the PAS and the MAIA-2 are reliable self-report tools to assess both components of body awareness (proprioception and interoception dimension, respectively).

Spatial-topographic nestedness of interoceptive regions within the networks of decision making and emotion regulation: Combining ALE meta-analysis and MACM analysis

Prominent theories propose that interoception modulates our behavioral and emotional responses involving decision-making and emotion regulation. Are the regions implicated in interoception also spatially related to and possibly nested within the networks of decision making and emotion regulation? Addressing this question, we performed three meta-analyses of functional magnetic resonance imaging studies to identify the regions that are commonly activated by the three domains using activation likelihood estimation (ALE). Additionally, we assessed the coactivation pattern of identified common regions using meta-analytic connectivity modeling (MACM). The results showed major overlaps of interoception with both decision making and emotion regulation in specifically the right dorsal anterior insula. The pairwise contrast analyses confirmed this finding and revealed conjunction-based activities in decision making and emotion regulation in the dorsal anterior cingulate cortex (dACC). MACM based on the identified insula revealed a widespread convergent coactivation pattern with the left anterior insula, dACC, and bilateral thalamus which, together, constitute the salience network. Among these co-activated regions, bilateral insula and the dACC were shared among all three domains. These results suggest that the regions mediating interoception including intero-exteroceptive integration and salience attribution are contained and thus spatially nested within the more extensive networks recruited during decision making and emotion regulation.

Left and right temporal-parietal junctions (TPJs) as "match/mismatch" hedonic machines: A unifying account of TPJ function

Experimental and theoretical studies have tried to gain insights into the involvement of the Temporal Parietal Junction (TPJ) in a broad range of cognitive functions like memory, attention, language, self-agency and theory of mind. Recent investigations have demonstrated the partition of the TPJ in discrete subsectors. Nonetheless, whether these subsectors play different roles or implement an overarching function remains debated. Here, based on a review of available evidence, we propose that the left TPJ codes both matches and mismatches between expected and actual sensory, motor, or cognitive events while the right TPJ codes mismatches. These operations help keeping track of statistical contingencies in personal, environmental, and conceptual space. We show that this hypothesis can account for the participation of the TPJ in disparate cognitive functions, including "humour", and explain: a) the higher incidence of spatial neglect in right brain damage; b) the different emotional reactions that follow left and right brain damage; c) the hemispheric lateralisation of optimistic bias mechanisms; d) the lateralisation of mechanisms that regulate routine and novelty behaviours. We propose that match and mismatch operations are aimed at approximating "free energy", in terms of the free energy principle of decision-making. By approximating "free energy", the match/mismatch TPJ system supports both information seeking to update one's own beliefs and the pleasure of being right in one's own' current choices. This renewed view of the TPJ has relevant clinical implications because the misfunctioning of TPJ-related "match" and "mismatch" circuits in unilateral brain damage can produce low-dimensional deficits of active-inference and predictive coding that can be associated with different neuropsychological disorders.

Exploring the role of interoception in autobiographical memory recollection

The way we perceive signals coming from the inside of the body (i.e., interoception) may influence the processing of information related to the self. In this study, we investigated whether interoceptive sensibility may play a role in autobiographical memory processes. We evaluated 41 healthy participants with a modified version of the Autobiographical Memory Test, also assessing specificity, vividness, emotional valence, and intensity for autobiographical and public memories. Participants completed a self-report questionnaire measuring interoceptive sensibility. Results showed that autobiographical memories were recalled with higher specificity, vividness, and emotional intensity than public memories. Interestingly, we found that participants with (self-reported) high interoceptive sensibility recalled more positive events in the autobiographical compared to the public condition. Our findings provided new evidence on the selective role of physiological aspects of bodily self-awareness in autobiographical memory, suggesting that interoception is fundamental for supporting adaptive emotion regulation processes when recollecting engrams related to the self.

Differential contributions of serotonergic and dopaminergic functional connectivity to the phenomenology of LSD

RATIONALE

LSD is the prototypical psychedelic. Despite a clear central role of the 5HT2a receptor in its mechanism of action, the contributions of additional receptors for which it shows affinity and agonist activity remain unclear.

OBJECTIVES

We employed receptor-enriched analysis of functional connectivity by targets (REACT) to explore differences in functional connectivity (FC) associated with the distributions of the primary targets of LSD-the 5HT1a, 5HT1b, 5HT2a, D1 and D2 receptors.

METHODS

We performed secondary analyses of an openly available dataset (N = 15) to estimate the LSD-induced alterations in receptor-enriched FC maps associated with these systems. Principal component analysis (PCA) was employed as a dimension reduction strategy for subjective experiences associated with LSD captured by the Altered States of Consciousness (ASC) questionnaire. Correlations between these principal components as well as VAS ratings of subjective effects with receptor-enriched FC were explored.

RESULTS

Compared to placebo, LSD produced differences in FC when the analysis was enriched with each of the primary serotonergic and dopaminergic receptors. Altered receptor-enriched FC showed relationships with the subjective effects of LSD on conscious experience, with serotonergic and dopaminergic systems being predominantly associated with perceptual effects and perceived selfhood as well as cognition respectively. These relationships were dissociable, with different receptors showing the same relationships within, but not between, the serotonergic and dopaminergic systems.

CONCLUSIONS

These exploratory findings provide new insights into the pharmacology of LSD and highlight the need for additional investigation of non-5HT2a-mediated mechanisms.

Embodying an artificial hand increases blood flow to the investigated limb [version 3; peer review: 2 approved]

Background

The autonomic nervous system is the main determinant of the blood flow directed towards a body part, and it is tightly connected to the representation of the body in the brain; would the experimental modulation of the sense of limb ownership affect its blood perfusion?

Methods

In healthy participants, we employed the rubber hand illusion paradigm to modulate limb ownership while we monitored the brachial artery blood flow and resistance index within the investigated limb.

Results

In all conditions with brush-stroking, we found an initial drop in the blood flow due to tactile stimulation. Subsequently, in the illusion condition (where both the rubber and real hand synchronous brush-stroking were present), the blood flow rose significantly faster and reached significantly higher values. Moreover, the increase in blood flow correlated with the extent of embodiment as measured by questionnaires and correlated negatively with the change of peripherical vascular resistance.

Conclusions

These findings suggest that modulating the representation of a body part impacts its blood perfusion.

Environment and body-brain interplay affect inhibition and decision-making

The fine-tuned interplay of brain and body underlies human ability to cope with changes in the internal and external milieus. Previous research showed that cardiac interoceptive changes (e.g., cardiac phase) affect cognitive functions, notably inhibition that is a key element for adaptive behaviour. Here we investigated the influence on cognition of vestibular signal, which provides the brain with sensory information about body position and movement. We used a centrifuge-based design to disrupt vestibular signal in healthy human volunteers while their inhibition and decision-making functions were assessed with the stop-signal paradigm. Participants performed the standard and a novel, sensorial version of the stop-signal task to determine whether disrupted vestibular signal influences cognition as a function of its relevance to the context. First, we showed that disrupted vestibular signal was associated with a larger variability of longest inhibition latencies, meaning that participants were even slower to inhibit in the trials where they had the most difficulty inhibiting. Second, we revealed that processing of bodily information, as required in the sensorial stop-signal task, also led to a larger variability of longest inhibition latencies, which was all the more important when vestibular signal was disrupted. Lastly, we found that such a degraded response inhibition performance was due in part to the acceleration of decision-making process, meaning that participants made a decision more quickly even when strength of sensory evidence was reduced. Taken together, these novel findings provide direct evidence that vestibular signal affects the cognitive functions of inhibition and decision-making.

Altered regional brain activity and functional connectivity patterns in major depressive disorder: A function of childhood trauma or diagnosis?

Childhood trauma (CT) is a non-specific risk factor for major depressive disorder (MDD). However, the neurobiological mechanisms of MDD with CT remain unclear. In the present study, we sought to determine the specific brain regions associated with CT and MDD etiology. Fractional amplitude of low-frequency fluctuation (fALFF) and functional connectivity (FC) analyses were performed to assess alterations of intrinsic brain activity in MDD with CT, MDD without CT, healthy controls with CT, and healthy controls without CT. Two-by-two factorial analyses were performed to examine the effects of the factors "MDD" and "CT" on fALFF and FC. Moderator analysis was used to explore whether the severity of depression moderated the relationship between CT and aberrant fALFF. We found that the etiological effects of MDD and CT exhibited negative impacts on brain dysfunction including altered fALFF in the left postcentral gyrus, left lingual gyrus, left paracentral lobule (PCL), and left cuneus. Decreased FC was observed in the following regions: (i) the left lingual gyrus seed and the left fusiform gyrus as well as the right calcarine cortex; (ii) the left PCL seed and the left supplementary motor area, left calcarine cortex, left precentral gyrus, and right cuneus; (iii) the left postcentral gyrus seed and left superior parietal lobule, right postcentral gyrus, and left precentral gyrus. Furthermore, the severity of depression acted as a moderator in the relationship between CT and aberrant fALFF in the left PCL. These data indicate that MDD patients with and without trauma exposure are clinically and neurobiologically distinct.

Structural Features Predict Sexual Trauma and Interpersonal Problems in Borderline Personality Disorder but Not in Controls: A Multi-Voxel Pattern Analysis

Child trauma plays an important role in the etiology of Bordeline Personality Disorder (BPD). Of all traumas, sexual trauma is the most common, severe and most associated with receiving a BPD diagnosis when adult. Etiologic models posit sexual abuse as a prognostic factor in BPD. Here we apply machine learning using Multiple Kernel Regression to the Magnetic Resonance Structural Images of 20 BPD and 13 healthy control (HC) to see whether their brain predicts five sources of traumas: sex abuse, emotion neglect, emotional abuse, physical neglect, physical abuse (Child Trauma Questionnaire; CTQ). We also applied the same analysis to predict symptom severity in five domains: affective, cognitive, impulsivity, interpersonal (Zanarini Rating Scale for Borderline Personality Disorder; Zan-BPD) for BPD patients only. Results indicate that CTQ sexual trauma is predicted by a set of areas including the amygdala, the Heschl area, the Caudate, the Putamen, and portions of the Cerebellum in BPD patients only. Importantly, interpersonal problems only in BPD patients were predicted by a set of areas including temporal lobe and cerebellar regions. Notably, sexual trauma and interpersonal problems were not predicted by structural features in matched healthy controls. This finding may help elucidate the brain circuit affected by traumatic experiences and connected with interpersonal problems BPD suffer from.

Attention to body parts prompts thermoregulatory reactions in Body Integrity Dysphoria

In healthy subjects, the transient perturbation of body part ownership is accompanied by regional skin temperature decrease. This observation leaves an open question about a possible body part-specific thermoregulatory response in pathological conditions, in which the sense of ownership over that body part is altered. For instance, Body Integrity Dysphoria (BID), a poorly understood neuropsychiatric disorder, is characterised by the non-acceptance of one or more of one's extremities. This unsettling feeling pervasively captures the individuals' attention towards the unwanted limb. Previous studies characterised BID in terms of absent ownership feeling with preserved ownership judgment. We explored for the first time whether this altered feeling is also associated with a specific thermoregulatory response. We recorded thermal image sequences of circumscribed regions of the limbs' skin in seven individuals with BID desiring to remove one leg while they were invited to focus their attention toward one particular limb (arm or leg). Their event-related thermoregulatory pattern was compared to a group of healthy matched controls. In individuals with BID but not in control persons, we found a bilateral decrease in leg temperature when focusing their attention on either the unwanted or accepted leg. The event-related thermoregulatory response for both upper limbs was similar between individuals with BID and healthy controls. Our results suggest that the alteration of the sense of body ownership in neuropsychiatric conditions such as BID may critically rest on specific event-related thermoregulatory patterns in response to modulation of attention to body parts.

Region-of-interest analysis approaches in neuroimaging studies of body ownership: An activation likelihood estimation meta-analysis

How do we feel that we own our body? By manipulating the integration of multisensory signals and creating the illusory experience of owning external body parts and entire bodies, researchers have investigated the neurofunctional correlates of body ownership. Recent attempts to synthesize the neuroimaging literature of body ownership through meta-analysis have shown partly inconsistent results. A large proportion of functional magnetic resonance imaging (fMRI) findings on body ownership include analyses based on regions of interest (ROIs). This approach can produce inflated findings when results are synthesized in meta-analyses. We conducted a systematic search of the fMRI literature of ownership of body parts and entire bodies. Three activation likelihood estimation (ALE) meta-analyses were conducted, testing the impact of including ROI-based findings. When both whole-brain and ROI-based results were included, frontal and posterior parietal multisensory areas were associated with body ownership. When only ROI-based results were included, larger areas of the frontal and posterior parietal cortices and the middle occipital gyrus were associated with body ownership. A whole-brain meta-analysis, excluding ROI-based results, found no significant convergence of activation across the brain. These findings highlight the difficulty of quantitatively synthesizing a neuroimaging field where a large part of the literature is based on findings from ROI-based analyses. We discuss these findings in the light of current practices within this field of research and highlight current problems of meta-analytic approaches of body ownership. We recommend the sharing of unthresholded data as a means to facilitate future meta-analyses of the neuroimaging literature of body ownership.

Embodying an artificial hand increases blood flow to the investigated limb

Background: The autonomic nervous system is the main determinant of the blood flow directed towards a body part, and it is tightly connected to the representation of the body in the brain; would the experimental modulation of the sense of ownership of the limb affect its blood perfusion? Methods: In healthy participants, we employed the rubber hand illusion paradigm to modulate limb ownership while we monitored the brachial artery blood flow and resistance of the investigated limb. Results: In all conditions with brush-stroking, we found an initial drop in the blood flow due to tactile stimulation. Subsequently, in the illusion condition where both the rubber and real hand experience synchronous brush-stroking, the blood flow rose significantly faster and reached significantly higher values. Moreover, the increase in blood flow correlated to the embodiment level measured by questionnaires and, negatively, to the change of peripherical vascular resistance. Conclusions: These findings demonstrate that modulating the representation of a body part impacts its blood perfusion.

Precision control for a flexible body representation

Adaptive body representation requires the continuous integration of multisensory inputs within a flexible 'body model' in the brain. The present review evaluates the idea that this flexibility is augmented by the contextual modulation of sensory processing 'top-down'; which can be described as precision control within predictive coding formulations of Bayesian inference. Specifically, I focus on the proposal that an attenuation of proprioception may facilitate the integration of conflicting visual and proprioceptive bodily cues. Firstly, I review empirical work suggesting that the processing of visual vs proprioceptive body position information can be contextualised 'top-down'; for instance, by adopting specific attentional task sets. Building up on this, I review research showing a similar contextualisation of visual vs proprioceptive information processing in the rubber hand illusion and in visuomotor adaptation. Together, the reviewed literature suggests that proprioception, despite its indisputable importance for body perception and action control, can be attenuated top-down (through precision control) to facilitate the contextual adaptation of the brain's body model to novel visual feedback.

Health emergencies and interoceptive sensibility modulate the perception of non-evidence-based drug use: Findings from the COVID-19 outbreak

Scientific evidence plays an important role in the therapeutic decision-making process. What happens when physicians are forced to make therapeutic decisions under uncertainty? The absence of scientific guidelines at the beginning of a pandemic due to an unknown virus, such as COVID-19, could influence the perceived legitimacy of the application of non-evidence-based therapeutic approaches. This paper reports on a test of this hypothesis, in which we administered an ad hoc questionnaire to a sample of 64 Italian physicians during the first wave of the COVID-19 pandemic in Italy (April 2020). The questionnaire statements regarding the legitimacy of off-label or experimental drugs were framed according to three different scenarios (Normality, Emergency and COVID-19). Furthermore, as the perception of internal bodily sensations (i.e., interoception) modulates the decision-making process, we tested participants' interoceptive sensibility using the Multidimensional Assessment of Interoceptive Awareness (MAIA). The results showed that participants were more inclined to legitimate non-evidence-based therapeutic approaches in the COVID-19 and Emergency scenarios than the Normality scenario. We also found that scores on the MAIA Trusting subscale positively predicted this difference. Our findings demonstrate that uncertain medical scenarios, involving a dramatic increase in patient volume and acuity, can increase risk-taking in therapeutic decision-making. Furthermore, individual characteristics of health care providers, such as interoceptive ability, should be taken into account when constructing models to prevent the breakdown of healthcare systems in cases of severe emergency.

Could Brain-Computer Interface Be a New Therapeutic Approach for Body Integrity Dysphoria?

Patients suffering from body integrity dysphoria (BID) desire to become disabled, arising from a mismatch between the desired body and the physical body. We focus here on the most common variant, characterized by the desire for amputation of a healthy limb. In most reported cases, amputation of the rejected limb entirely alleviates the distress of the condition and engenders substantial improvement in quality of life. Since BID can lead to life-long suffering, it is essential to identify an effective form of treatment that causes the least amount of alteration to the person's anatomical structure and functionality. Treatment methods involving medications, psychotherapy, and vestibular stimulation have proven largely ineffective. In this hypothesis article, we briefly discuss the characteristics, etiology, and current treatment options available for BID before highlighting the need for new, theory driven approaches. Drawing on recent findings relating to functional and structural brain correlates of BID, we introduce the idea of brain-computer interface (BCI)/neurofeedback approaches to target altered patterns of brain activity, promote re-ownership of the limb, and/or attenuate stress and negativity associated with the altered body representation.

Presence, flow, and narrative absorption: an interdisciplinary theoretical exploration with a new spatiotemporal integrated model based on predictive processing

Presence, flow, narrative absorption, immersion, transportation, and similar subjective phenomena are studied in many different disciplines, mostly in relation to mediated experiences (books, film, VR, games). Moreover, since real, virtual, or fictional agents are often involved, concepts like identification and state empathy are often linked to engaging media use. Based on a scoping review that identified similarities in the wording of various questionnaire items conceived to measure different phenomena, we categorize items into the most relevant psychological aspects and use this categorization to propose an interdisciplinary systematization. Then, based on a framework of embodied predictive processing, we present a new cognitive model of presence-related phenomena for mediated and non-mediated experiences, integrating spatial and temporal aspects and also considering the role of fiction and media design. Key processes described within the model are: selective attention, enactment of intentions, and interoception. We claim that presence is the state of perceived successful agency of an embodied mind able to correctly enact its predictions. The difference between real-life and simulated experiences ("book problem," "paradox of fiction") lays in the different precision weighting of exteroceptive and interoceptive signals.

Subsurface Confinement: Evidence from Submariners of the Benefits of Mindfulness

Objectives

The subsurface ballistic missile nuclear submarine (SSBN) is an extreme professional environment in which personnel are both isolated and confined during patrols, which can last longer than 2 months. This environment is known to degrade submariners’ mood and cognition.

Methods

This exploratory, empirical study followed a cohort of 24 volunteer submariners. Dispositional mindfulness was assessed with the Freiburg Mindfulness Inventory, in order to identify two groups (mindful and non-mindful) and compare change in emotional state, interoception, and health behaviors during the patrol.

Results

Overall, psychological health deteriorated during the patrol. However, mindful submariners demonstrated better psychological adaptation and interoception than the non-mindful group. This was associated with better subjective health behaviors (sleeping and eating).

Conclusions

Dispositional mindfulness appears to protect against the negative effects of long-term containment in a professional environment, such as a submarine patrol. Our work highlights that mindfulness may help individuals to cope with stress in such situations. Developing mindfulness could also be an important preventive healthcare measure during quarantine imposed by the outbreak of a serious infectious disease.

Exploring the Interaction Between Handedness and Body Parts Ownership by Means of the Implicit Association Test

The experience of owning a body is built upon the integration of exteroceptive, interoceptive, and proprioceptive signals. Recently, it has been suggested that motor signals could be particularly important in producing the feeling of body part ownership. One thus may hypothesize that the strength of this feeling may not be spatially uniform; rather, it could vary as a function of the degree by which different body parts are involved in motor behavior. Given that our dominant hand plays a leading role in our motor behavior, we hypothesized that it could be more strongly associated with one’s self compared to its non-dominant counterpart. To explore whether this possible asymmetry manifests as a stronger implicit association of the right hand (vs left hand) with the self, we administered the Implicit Association Test to a group of 70 healthy individuals. To control whether this asymmetric association is human-body specific, we further tested whether a similar asymmetry characterizes the association between a right (vs left) animal body part with the concept of self, in an independent sample of subjects (N = 70, 140 subjects total). Our results revealed a linear relationship between the magnitude of the implicit association between the right hand with the self and the subject’s handedness. In detail, the strength of this association increased as a function of hand preference. Critically, the handedness score did not predict the association of the right-animal body part with the self. These findings suggest that, in healthy individuals, the dominant and non-dominant hands are differently perceived at an implicit level as belonging to the self. We argue that such asymmetry may stem from the different roles that the two hands play in our adaptive motor behavior.

Time is body: Multimodal evidence of crosstalk between interoception and time estimation

Theoretical approaches propose a blending between interoception and time estimation. Interoception might constitute a neurophysiological mechanism for encoding duration. However, no study has assessed the convergence between interoception and time estimation using behavioral, neurophysiological, and functional anatomy signatures. We examined the multimodal convergence between interoception and time estimation using a two-fold approach. In study 1, we developed a dual design combining interoception (measuring heartbeat detection - HBD, and heartbeat evoked potential - HEP) with a time estimation paradigm (TEP, estimation of duration of a 120 s interval). In study 2, we performed a conjoint metanalysis (Multi-level Kernel Density Analysis, MKDA) of neuroimaging, including reports of interoception and time estimation. Both studies provide convergent evidence of time estimation's significant involvement in behavioral, electrophysiological (enhanced HEP), and neuroimaging (overlapping cluster in the right insula and operculum) signatures of interoception. Convergent results from both studies offer direct support for a shared mechanism of interoception and time estimation.

Interoceptive Awareness Is Negatively Related to the Exteroceptive Manipulation of Bodily Self-Location

The perception of being located within one's body (i.e., bodily self-location) is an essential feature of everyday self-experience. However, by manipulating exteroceptive input, healthy participants can easily be induced to perceive themselves as being spatially dislocated from their physical bodies. It has previously been suggested that interoception, i.e., the processing of inner physiological signals, contributes to the stability of body representations; however, this relationship has not previously been tested for different dimensions of interoception and bodily self-location. In the present study, using an advanced automatized setup, we systematically manipulated participants' perspective of their own body (first- vs third-person perspective) as well as the synchrony of visuotactile stimulation (synchronous vs asynchronous). The malleability of bodily self-location was assessed using a questionnaire targeting in-body and out-of-body experiences. Participants also performed a heartbeat discrimination task to assess their interoceptive accuracy (behavioral performance), interoceptive sensibility (confidence in their interoceptive abilities), and interoceptive awareness (meta-cognitive representation of interoceptive signals). Bodily self-location was significantly influenced by perspective, with third-person perspective being associated with stronger out-of-body experiences compared to first-person perspective. Furthermore, there was a significant perspective × stimulation interaction, with subsequent analyses showing that participants reported out-of-body experiences particularly under third-person perspective combined with synchronous visuotactile stimulation. Correlation and regression analyses revealed that meta-cognitive interoceptive awareness was specifically and negatively related to the exteroceptively mediated malleability of body experiences. These results indicate that the perception of the self being located within one's body relies on the interaction of exteroceptive input and higher-order interoceptive abilities. This has implications for theoretical considerations about the bodily self in health as well as for the understanding of disturbed bodily self-processing in clinical contexts.

Bilateral skin temperature drop and warm sensibility decrease following modulation of body part ownership through mirror-box illusion

The implicit and explicit awareness of owning a body and its parts is a constant accompaniment in our everyday life and our interaction with the outside world. The way in which we build and maintain a coherent sense of body ownership is not fully understood. It has been postulated that the integration between exteroceptive, interoceptive, and proprioceptive signals may play a fundamental role in the sense of body ownership. For instance, studies on healthy subjects and brain-damaged patients have suggested that alterations in the sense of body ownership are coupled with autonomic signal changes, such as thermoregulatory reactions. However, the available evidence is conflicting, possibly due to shortcomings in the experimental paradigm that previous studies have adopted. In this study, we explore the relationship between body ownership, thermoregulation, and thermal sensitivity through a novel application of the mirror-box illusion paradigm, overcoming some of the limitations of previous studies. We find a bilateral decrease in hand skin temperature, together with reduced thermal sensitivity for warm thermal stimuli following the induction of the illusion of ownership towards the participant's reflected hand. These findings demonstrate the importance of the orchestration of exteroceptive (e.g., visual), autonomic (e.g., body temperature) and proprioceptive (e.g., position and movement of the body) signals in maintaining a coherent sense of body ownership.

Skipping a Beat: Heartbeat-Evoked Potentials Reflect Predictions during Interoceptive-Exteroceptive Integration

Several theories propose that emotions and self-awareness arise from the integration of internal and external signals and their respective precision-weighted expectations. Supporting these mechanisms, research indicates that the brain uses temporal cues from cardiac signals to predict auditory stimuli and that these predictions and their prediction errors can be observed in the scalp heartbeat-evoked potential (HEP). We investigated the effect of precision modulations on these cross-modal predictive mechanisms, via attention and interoceptive ability. We presented auditory sequences at short (perceived synchronous) or long (perceived asynchronous) cardio-audio delays, with half of the trials including an omission. Participants attended to the cardio-audio synchronicity of the tones (internal attention) or the auditory stimuli alone (external attention). Comparing HEPs during omissions allowed for the observation of pure predictive signals, without contaminating auditory input. We observed an early effect of cardio-audio delay, reflecting a difference in heartbeat-driven expectations. We also observed a larger positivity to the omissions of sounds perceived as synchronous than to the omissions of sounds perceived as asynchronous when attending internally only, consistent with the role of attentional precision for enhancing predictions. These results provide support for attentionally modulated cross-modal predictive coding and suggest a potential tool for investigating its role in emotion and self-awareness.

A multidimensional and multi-feature framework for cardiac interoception

Interoception (the sensing of inner-body signals) is a multi-faceted construct with major relevance for basic and clinical neuroscience research. However, the neurocognitive signatures of this domain (cutting across behavioral, electrophysiological, and fMRI connectivity levels) are rarely reported in convergent or systematic fashion. Additionally, various controversies in the field might reflect the caveats of standard interoceptive accuracy (IA) indexes, mainly based on heartbeat detection (HBD) tasks. Here we profit from a novel IA index (md) to provide a convergent multidimensional and multi-feature approach to cardiac interoception. We found that outcomes from our IA-md index are associated with -and predicted by- canonical markers of interoception, including the hd-EEG-derived heart-evoked potential (HEP), fMRI functional connectivity within interoceptive hubs (insular, somatosensory, and frontal networks), and socio-emotional skills. Importantly, these associations proved more robust than those involving current IA indexes. Furthermore, this pattern of results persisted when taking into consideration confounding variables (gender, age, years of education, and executive functioning). This work has relevant theoretical and clinical implications concerning the characterization of cardiac interoception and its assessment in heterogeneous samples, such as those composed of neuropsychiatric patients.

Building the bodily self-awareness: Evidence for the convergence between interoceptive and exteroceptive information in a multilevel kernel density analysis study

Exteroceptive and interoceptive signals shape and sustain the bodily self-awareness. The existence of a set of brain areas, supporting the integration of information coming from the inside and the outside of the body in building the sense of bodily self-awareness has been postulated, yet the evidence remains limited, a matter of discussion never assessed quantitatively. With the aim of unrevealing where in the brain interoceptive and exteroceptive signals may converge, we performed a meta-analysis on imaging studies of the sense of body ownership, modulated by external visuotactile stimulation, and studies on interoception, which involves the self-awareness for internal bodily sensations. Using a multilevel kernel density analysis, we found that processing of stimuli of the two domains converges primarily in the supramarginal gyrus bilaterally. Furthermore, we found a right-lateralized set of areas, including the precentral and postcentral, and superior temporal gyri. We discuss these results and propose this set of areas as ideal candidates to match multiple body-related signals contributing to the creation of a multidimensional representation of the bodily self.