Altered Interoceptive Processing in Generalized Anxiety Disorder-A Heartbeat-Evoked Potential Research

Posture-Dependent Modulation of Interoceptive Processing in Young Male Participants: A Heartbeat-Evoked Potential Study

Interoception, the internal perception of bodily states such as heartbeat and hunger, plays a crucial role in shaping cognitive and emotional states. Since postural control affects cognitive and emotional processing, exploring postural effects on interoception could help uncover the neural mechanisms underlying its effects on cognition and emotion. In this study, we aimed to investigate how different postures affect interoception by using heartbeat-evoked potentials (HEPs), which reflect the cortical processing of cardiac signals. Two experiments were conducted; Experiment 1 involved 47 healthy male participants comparing sitting and standing postures, and Experiment 2 involved 24 healthy male participants comparing stable and unstable standing conditions. HEPs were analyzed using cluster-based permutation analysis to identify statistically significant spatiotemporal clusters. In Experiment 1, significant clusters were identified over central electrodes (Cz, C1, C2, FCz, and FC1) within the post-R-wave interval of 304-572 ms, revealing significantly lower HEP amplitudes during standing compared to sitting [W = 80, p < 0.001, r = 0.62]. In Experiment 2, HEP amplitudes were significantly lower during unstable standing compared to stable standing [t(20) = 2.9, p = 0.0099, d = 0.62]. Furthermore, we found no significant correlations between HEP changes and physiological changes such as cardiac activity and periodic and aperiodic brain activity. These findings suggest postural differences modulate interoceptive processing, with standing postures attenuating HEP amplitudes, probably because of a redistribution of attentional resources from interoceptive to somatosensory (proprioceptive) and vestibular processing, necessary for maintaining standing posture. This study provides insights into the neural mechanisms underlying posture-interoception interaction.

Allostatic Interoceptive Overload Across Psychiatric and Neurological Conditions

Emerging theories emphasize the crucial role of allostasis (anticipatory and adaptive regulation of the body's biological processes) and interoception (integration, anticipation, and regulation of internal bodily states) in adjusting physiological responses to environmental and bodily demands. In this review, we explore the disruptions in integrated allostatic interoceptive mechanisms in psychiatric and neurological disorders, including anxiety, depression, Alzheimer's disease, and frontotemporal dementia. We assess the biological mechanisms associated with allostatic interoception, including whole-body cascades, brain structure and function of the allostatic interoceptive network, heart-brain interactions, respiratory-brain interactions, the gut-brain-microbiota axis, peripheral biological processes (inflammatory, immune), and epigenetic pathways. These processes span psychiatric and neurological conditions and call for developing dimensional and transnosological frameworks. We synthesize new pathways to understand how allostatic interoceptive processes modulate interactions between environmental demands and biological functions in brain disorders. We discuss current limitations of the framework and future transdisciplinary developments. This review opens a new research agenda for understanding how allostatic interoception involves brain predictive coding in psychiatry and neurology, allowing for better clinical application and the development of new therapeutic interventions.

The Limbic System in Co-Occurring Substance Use and Anxiety Disorders: A Narrative Review Using the RDoC Framework

Substance use disorders (SUDs) and anxiety disorders (ADs) are highly comorbid, a co-occurrence linked to worse clinical outcomes than either condition alone. While the neurobiological mechanisms involved in SUDs and anxiety disorders are intensively studied separately, the mechanisms underlying their comorbidity remain an emerging area of interest. This narrative review explores the neurobiological processes underlying this comorbidity, using the Research Domain Criteria (RDoC) framework to map disruptions in positive valence, negative valence, and cognitive systems across the three stages of the addiction cycle: binge/intoxication, withdrawal/negative affect, and preoccupation/anticipation. Anxiety and substance use play a reciprocal role at each stage of addiction, marked by significant psychosocial impairment and dysregulation in the brain. A more thorough understanding of the neural underpinnings involved in comorbid SUDs and anxiety disorders will contribute to more tailored and effective therapeutic interventions and assessments.

Exploring the Link Between Interoception and Symptom Severity in Premature Ventricular Contractions

Background/Objectives: The physiological basis underlying symptomatic versus asymptomatic premature ventricular contractions (PVCs) remains poorly understood. However, symptomatic PVCs can significantly impair quality of life. In patients without structural heart disease, symptom intensity is crucial for guiding management strategies and determining the need for medical or surgical intervention. In this study, we aimed, for the first time, to examine the associations between PVC symptoms and cardiac interoception. Methods: This study included 34 participants with PVCs (20 women; median age = 42 years; 17 participants had asymptomatic PVCs) without concomitant disorders. Interoception was assessed through interoceptive accuracy (IA) probed by two behavioral tests-mental tracking (MT) and heartbeat detection (HBD)-and the neurophysiological marker of cardiac interoception, the heartbeat-evoked potentials (HEPs). Symptom intensity scores reported by patients served as the response variable in the regression analysis, with IA and HEP as predictors. Other factors such as sex, age, percent of body fat, trait anxiety, and alexithymia were added to the models as confounding variables. Results: IAMT was significantly higher in patients with symptomatic PVCs. IAMT and HEP modulation for the HBD task were associated with symptom intensity. A combined regression model incorporating both metrics showed the highest predictive accuracy for symptom severity. Adding confounding variables improved model quality (lower AIC); however, only the male sex emerged as a significant negative predictor for symptom intensity. Conclusions: Our findings confirm a significant association between interoception and PVC symptom severity. Integrating behavioral and neurophysiological interoception measures enhances symptom prediction accuracy, suggesting new ways to develop diagnostic and non-invasive treatment strategies targeting interoception in PVC management.

Sensory Processing and Anxiety: Within and Beyond the Autism Spectrum

In this article, we briefly overview how the expression, measurement, and treatment of anxiety in autism may be different from the general population. We review the literature on links between sensory processing differences and anxiety, which show transdiagnostic patterns but are an especially prominent feature of anxiety in autism. Specifically, we focus on how the sense of interoception, i.e., how we perceive sensory information from within our bodies, contributes to anxiety in autism. We present new findings integrating multimodal interoceptive measures and total anxiety symptoms in a sample of n = 38 non-autistic and n = 43 autistic individuals, ages 8-55 years. Using principal components analysis, we found two components relating to interoceptive confusion (i.e., self-reported ability to localize and interpret interoceptive cues): one component that closely relates to anxiety symptoms and one component that is distinct from anxiety. Interoceptive perception (i.e., performance on a lab-based task) was uniformly related to interoceptive confusion when distinguished from anxiety but showed complex relations with total anxiety symptoms. Combined, these findings suggest meaningful subtypes of interoceptive difficulties and their interrelationship with anxiety. We present conclusions and future directions for consideration of individual differences, toward creating a personalized understanding of anxiety-interoception links.

Exploring the relationship between cardiac awareness and balance

Postural balance requires the interplay between several physiological signals. Indirect evidence suggests that the perception of signals arising from the autonomic nervous system might play a role (e.g. cardiac awareness). Here, we tested this hypothesis by investigating the relationship between postural control and cardiac awareness (i.e. interoception) in a sample of N = 70 healthy individuals. Postural control was measured using a medical robotic device, while cardiac awareness was evaluated using the heartbeat counting task. A within-subject design included two platform configurations (static, unstable) and two visual feedback conditions (eyes open, eyes closed). For each condition, we measured the sway area and the range of oscillation of the platform, as well as the range of oscillation and the quantity of movement of participants' trunk. In the "platform unstable, eyes closed" condition, participants with higher cardiac awareness demonstrated a significantly smaller sway area and reduced oscillations of both the platform and their trunk. These findings hint at a potential link between interoception and postural control, suggesting that the perception of internal body signals might sustain balance.

The Insular Cortex: An Interface Between Sensation, Emotion and Cognition

The insula is a complex brain region central to the orchestration of taste perception, interoception, emotion, and decision-making. Recent research has shed light on the intricate connections between the insula and other brain regions, revealing the crucial role of this area in integrating sensory, emotional, and cognitive information. The unique anatomical position and extensive connectivity allow the insula to serve as a critical hub in the functional network of the brain. We summarize its role in interoceptive and exteroceptive sensory processing, illustrating insular function as a bridge connecting internal and external experiences. Drawing on recent research, we delineate the insular involvement in emotional processes, highlighting its implications in psychiatric conditions, such as anxiety, depression, and addiction. We further discuss the insular contributions to cognition, focusing on its significant roles in time perception and decision-making. Collectively, the evidence underscores the insular function as a dynamic interface that synthesizes diverse inputs into coherent subjective experiences and decision-making processes. Through this review, we hope to highlight the importance of the insula as an interface between sensation, emotion, and cognition, and to inspire further research into this fascinating brain region.

Factor structure and psychometric properties of the Body Perception Questionnaire-Short Form (BPQ-SF); The Persian version

BACKGROUND

Body perception is considered an important physiological marker in physical and mental disorders, therefore, its valid and reliable quantification is indeed necessary. Due to the lack of a Persian version of an instrument with validated psychometric properties for evaluating body perception, this study aimed to investigate the factorial structure, reliability, and validity of body perception questionnaire-Short Form (BPQ-SF) among Iranian adults.

METHODS

A total of 748 participants (mean age = 31.74; 57%female) were included in the analysis. Participants were recruited using the online survey method. Confirmatory factor analysis (CFA) was performed and concurrent validity was determined by computing Pearson's correlation coefficient between BPQ_SF, Depression Anxiety Stress Scale (DASS), and somatization subscale of Symptom-Checklist-90 (SOM). Internal consistency (using Cronbach's alpha and McDonald's omega), and composite reliability were also evaluated.

RESULTS

The result of the CFA yielded three factors: Body Awareness, Subdiaphragmatic Reactivity, and Supradiaphragmatic Reactivity. Cronbach's alpha values for all BPQ_SF items were 0.94. Moreover, Concurrent validity between BPQ, SOM, and DASS was determined to be between 0.44 to 0.94. and had good internal consistency (McDonald's Omega range: .74-.93 Cronbach's alpha range: .76-.94).

CONCLUSIONS

The BPQ-SF demonstrated good psychometric properties among Iranians thus can be used to reliably assess body perception.

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.

Heartbeat-evoked neural response abnormalities in generalized anxiety disorder during peripheral adrenergic stimulation

Hyperarousal symptoms in generalized anxiety disorder (GAD) are often incongruent with the observed physiological state, suggesting that abnormal processing of interoceptive signals is a characteristic feature of the disorder. To examine the neural mechanisms underlying interoceptive dysfunction in GAD, we evaluated whether adrenergic modulation of cardiovascular signaling differentially affects the heartbeat-evoked potential (HEP), an electrophysiological marker of cardiac interoception, during concurrent electroencephalogram and functional magnetic resonance imaging (EEG-fMRI) scanning. Intravenous infusions of the peripheral adrenergic agonist isoproterenol (0.5 and 2.0 micrograms, μg) were administered in a randomized, double-blinded and placebo-controlled fashion to dynamically perturb the cardiovascular system while recording the associated EEG-fMRI responses. During the 0.5 μg isoproterenol infusion, the GAD group (n = 24) exhibited significantly larger changes in HEP amplitude in an opposite direction than the healthy comparison (HC) group (n = 24). In addition, the GAD group showed significantly larger absolute HEP amplitudes than the HC group during saline infusions, when cardiovascular tone did not increase. No significant group differences in HEP amplitude were identified during the 2.0 μg isoproterenol infusion. Using analyzable blood oxygenation level-dependent fMRI data from participants with concurrent EEG-fMRI data (21 GAD and 21 HC), we found that the aforementioned HEP effects were uncorrelated with fMRI signals in the insula, ventromedial prefrontal cortex, dorsal anterior cingulate cortex, amygdala, and somatosensory cortex, brain regions implicated in cardiac signal processing in prior fMRI studies. These findings provide additional evidence of dysfunctional cardiac interoception in GAD and identify neural processes at the electrophysiological level that may be independent from blood oxygen level-dependent responses during peripheral adrenergic stimulation.

Low-intensity focused ultrasound to the human insular cortex differentially modulates the heartbeat-evoked potential: a proof-of-concept study

Background

The heartbeat evoked potential (HEP) is a brain response time-locked to the heartbeat and a potential marker of interoceptive processing. The insula and dorsal anterior cingulate cortex (dACC) are brain regions that may be involved in generating the HEP. Low-intensity focused ultrasound (LIFU) is a non-invasive neuromodulation technique that can selectively target sub-regions of the insula and dACC to better understand their contributions to the HEP.

Objective

Proof-of-concept study to determine whether LIFU modulation of the anterior insula (AI), posterior insula (PI), and dACC influences the HEP.

Methods

In a within-subject, repeated-measures design, healthy human participants (n=16) received 10 minutes of stereotaxically targeted LIFU to the AI, PI, dACC or Sham at rest during continuous electroencephalography (EEG) and electrocardiography (ECG) recording on separate days. Primary outcome was change in HEP amplitudes. Relationships between LIFU pressure and HEP changes were examined using linear mixed modelling. Peripheral indices of visceromotor output including heart rate and heart rate variability (HRV) were explored between conditions.

Results

Relative to sham, LIFU to the PI, but not AI or dACC, decreased HEP amplitudes; this was partially explained by increased LIFU pressure. LIFU did not affect time or frequency dependent measures of HRV.

Conclusions

These results demonstrate the ability to modulate HEP amplitudes via non-invasive targeting of key interoceptive brain regions. Our findings have implications for the causal role of these areas in bottom-up heart-brain communication that could guide future work investigating the HEP as a marker of interoceptive processing in healthy and clinical populations.

Heartbeat-evoked neural response abnormalities in generalized anxiety disorder during peripheral adrenergic stimulation

Hyperarousal symptoms in generalized anxiety disorder (GAD) are often incongruent with the observed physiological state, suggesting that abnormal processing of interoceptive signals is a characteristic feature of the disorder. To examine the neural mechanisms underlying interoceptive dysfunction in GAD, we evaluated whether adrenergic modulation of cardiovascular signaling differentially affects the heartbeat evoked potential (HEP), an electrophysiological marker of cardiac interoception, during concurrent electroencephalogram and functional magnetic resonance imaging (EEG-fMRI) scanning. Intravenous infusions of the peripheral adrenergic agonist isoproterenol (0.5 and 2.0 micrograms, μg) were administered in a randomized, double-blinded and placebo-controlled fashion to dynamically perturb the cardiovascular system while recording the associated EEG-fMRI responses. During the 0.5 μg isoproterenol infusion, the GAD group (n=24) exhibited significantly larger changes in HEP amplitude in an opposite direction than the HC group (n=24). In addition, the GAD group showed significantly larger absolute HEP amplitudes than HC during saline infusions, when cardiovascular tone did not increase. No significant group differences in HEP amplitude were identified during the 2.0 μg isoproterenol infusion. Using analyzable blood oxygenation level dependent fMRI data from participants with concurrent EEG-fMRI data (21 GAD and 21 HC), we found that the aforementioned HEP effects were uncorrelated with fMRI signals in the insula, ventromedial prefrontal cortex, dorsal anterior cingulate cortex, amygdala, and somatosensory cortex, brain regions implicated in cardiac signal processing according to prior fMRI studies. These findings provide additional evidence of dysfunctional cardiac interoception in GAD and identify neural processes at the electrophysiological level that may be independent from blood oxygen level-dependent responses during peripheral adrenergic stimulation.

A Primer on Interoception and its Importance in Psychiatry

Interoception is the perception of signals from inside the body. It plays a significant role in the nervous, cardiovascular, respiratory, gastrointestinal, genitourinary, and endocrine systems. It is also closely related to the autonomic nervous system and inflammatory pathways and plays a significant role in our optimal functioning. Recently, interoception has gained more attention in neuropsychiatric research. Anatomical and physiological aspects of interoception like relevant brain areas, the role of the vagus nerve, and the autonomic nervous system are gradually being understood. Different facets of interoception like interoceptive attention, detection, magnitude, discrimination, accuracy, awareness, and appraisal have been proposed and their assessments and importance are being evaluated. Further, interoception is often dysregulated or abnormal in psychiatric disorders. It has been implicated in the psychopathology, etiopathogenesis, clinical features and treatment of mood, anxiety, psychotic, personality and addiction-related disorders. This narrative review attempts to provide a nuanced understanding of the pathway(s), components, functions, assessments, and problems of interoception and will help us to detect its disturbances and evaluate its impact on psychiatric disorders, leading to a better perspective and management. This will also advance interoception-related research.

Brain State Relays Self-Processing and Heartbeat-Evoked Cortical Responses

The self has been proposed to be grounded in interoceptive processing, with heartbeat-evoked cortical activity as a neurophysiological marker of this processing. However, inconsistent findings have been reported on the relationship between heartbeat-evoked cortical responses and self-processing (including exteroceptive- and mental-self-processing). In this review, we examine previous research on the association between self-processing and heartbeat-evoked cortical responses and highlight the divergent temporal-spatial characteristics and brain regions involved. We propose that the brain state relays the interaction between self-processing and heartbeat-evoked cortical responses and thus accounts for the inconsistency. The brain state, spontaneous brain activity which highly and continuously changes in a nonrandom way, serves as the foundation upon which the brain functions and was proposed as a point in an extremely high-dimensional space. To elucidate our assumption, we provide reviews on the interactions between dimensions of brain state with both self-processing and heartbeat-evoked cortical responses. These interactions suggest the relay of self-processing and heartbeat-evoked cortical responses by brain state. Finally, we discuss possible approaches to investigate whether and how the brain state impacts the self-heart interaction.

Modelling mood updating: a proof of principle study

BACKGROUND

Recent developments in computational psychiatry have led to the hypothesis that mood represents an expectation (prior belief) on the likely interoceptive consequences of action (i.e. emotion). This stems from ideas about how the brain navigates its external world by minimising an upper bound on surprisal (free energy) of sensory information and echoes developments in other perceptual domains.

AIMS

In this paper we aim to present a simple partial observable Markov decision process that models mood updating in response to stressful or non-stressful environmental fluctuations while seeking to minimise surprisal in relation to prior beliefs about the likely interoceptive signals experienced with specific actions (attenuating or amplifying stress and pleasure signals).

METHOD

We examine how, by altering these prior beliefs we can model mood updating in depression, mania and anxiety.

RESULTS

We discuss how these models provide a computational account of mood and its related psychopathology and relate it to previous research in reward processing.

CONCLUSIONS

Models such as this can provide hypotheses for experimental work and also open up the potential modelling of predicted disease trajectories in individual patients.

Central control of cardiac activity as assessed by intra-cerebral recordings and stimulations

Some of the most important integrative control centers for the autonomic nervous system are located in the brainstem and the hypothalamus. However, growing recent neuroimaging evidence support that a set of cortical regions, named the central autonomic network (CAN), is involved in autonomic control and seems to play a major role in continuous autonomic cardiac adjustments to high-level emotional, cognitive or sensorimotor cortical activities. Intracranial explorations during stereo-electroencephalography (SEEG) offer a unique opportunity to address the question of the brain regions involved in heart-brain interaction, by studying: (i) direct cardiac effects produced by the electrical stimulation of specific brain areas; (ii) epileptic seizures inducing cardiac modifications; (iii) cortical regions involved in cardiac interoception and source of cardiac evoked potentials. In this review, we detail the available data assessing cardiac central autonomic regulation using SEEG, address the strengths and also the limitations of this technique in this context, and discuss perspectives. The main cortical regions that emerge from SEEG studies as being involved in cardiac autonomic control are the insula and regions belonging to the limbic system: the amygdala, the hippocampus, and the anterior and mid-cingulate. Although many questions remain, SEEG studies have already demonstrated afferent and efferent interactions between the CAN and the heart. Future studies in SEEG should integrate these afferent and efferent dimensions as well as their interaction with other cortical networks to better understand the functional heart-brain interaction.

Difference analysis of multidimensional electroencephalogram characteristics between young and old patients with generalized anxiety disorder

Growing evidences indicate that age plays an important role in the development of mental disorders, but few studies focus on the neuro mechanisms of generalized anxiety disorder (GAD) in different age groups. Therefore, this study attempts to reveal the neurodynamics of Young_GAD (patients with GAD under the age of 50) and Old_GAD (patients with GAD over 50 years old) through statistical analysis of multidimensional electroencephalogram (EEG) features and machine learning models. In this study, 10-min resting-state EEG data were collected from 45 Old_GAD and 33 Young_GAD. And multidimensional EEG features were extracted, including absolute power (AP), fuzzy entropy (FE), and phase-lag-index (PLI), on which comparison and analyses were performed later. The results showed that Old_GAD exhibited higher power spectral density (PSD) value and FE value in beta rhythm compared to theta, alpha1, and alpha2 rhythms, and functional connectivity (FC) also demonstrated significant reorganization of brain function in beta rhythm. In addition, the accuracy of machine learning classification between Old_GAD and Young_GAD was 99.67%, further proving the feasibility of classifying GAD patients by age. The above findings provide an objective basis in the field of EEG for the age-specific diagnosis and treatment of GAD.

A predictive coding framework of allostatic-interoceptive overload in frontotemporal dementia

Recent allostatic-interoceptive explanations using predictive coding models propose that efficient regulation of the body's internal milieu is necessary to correctly anticipate environmental needs. We review this framework applied to understanding behavioral variant frontotemporal dementia (bvFTD) considering both allostatic overload and interoceptive deficits. First, we show how this framework could explain divergent deficits in bvFTD (cognitive impairments, behavioral maladjustment, brain atrophy, fronto-insular-temporal network atypicality, aberrant interoceptive electrophysiological activity, and autonomic disbalance). We develop a set of theory-driven predictions based on levels of allostatic interoception associated with bvFTD phenomenology and related physiopathological mechanisms. This approach may help further understand the disparate behavioral and physiopathological dysregulations of bvFTD, suggesting targeted interventions and strengthening clinical models of neurological and psychiatric disorders.

Effects of 24-h acute total sleep deprivation on physiological coupling in healthy young adults

Sleep deprivation is associated with dysregulation of the autonomic nervous system, adverse cardiovascular events, cognitive and complex motor performance impairment. Less is known about the effects of acute total sleep deprivation (ATSD) on physiological coupling. We aimed to determine the effects of 24-h ATSD on the physiological coupling between complex subsystems by evaluating the cardiorespiratory, cardiovascular and cortico-cardiac interactions. This study enrolled 38 young healthy participants aged 23.2 ± 2.4 years. Multiple synchronous physiological signals including electrocardiography, photoplethysmography, bio-electrical impedance, electroencephalography, and continuous hemodynamic data, were performed over a baseline night after regular sleep and after a night with 24-h ATSD in the supine position. The magnitude squared coherence, phase synchronization index, and heartbeat evoked potential amplitudes, were obtained from 10-min synchronous physiological recordings to estimate the coupling strength between two time series. Parameters of hemodynamic characteristics and heart rate variability were also calculated to quantify autonomic regulation. Results indicated that the magnitude squared coherence (0.38 ± 0.17 vs. 0.29 ± 0.12, p = 0.015) between respiration and heart rate variability along with the magnitude squared coherence (0.36 ± 0.18 vs. 0.27 ± 0.13, p = 0.012) between respiration and pulse transit time were significantly decreased after 24-h ATSD. There were no significant differences (all p > 0.05) in phase synchronization indices, heartbeat evoked potential amplitudes as well as other analyzed measurements between baseline and 24-h ATSD states. We conclude that exposure to 24-h ATSD appears to weaken the cardiorespiratory and respiratory-cardiovascular coupling strength of young healthy adults. These findings suggest that physiological coupling analysis may serve as a complementary approach for characterizing and understanding the complex effects of sleep deprivation.

Enhanced top-down sensorimotor processing in somatic anxiety

Functional neuroimaging research on anxiety has traditionally focused on brain networks associated with the psychological aspects of anxiety. Here, instead, we target the somatic aspects of anxiety. Motivated by the growing appreciation that top-down cortical processing plays a crucial role in perception and action, we used resting-state functional MRI data from the Human Connectome Project and Dynamic Causal Modeling (DCM) to characterize effective connectivity among hierarchically organized regions in the exteroceptive, interoceptive, and motor cortices. In people with high (fear-related) somatic arousal, top-down effective connectivity was enhanced in all three networks: an observation that corroborates well with the phenomenology of anxiety. The anxiety-associated changes in connectivity were sufficiently reliable to predict whether a new participant has mild or severe somatic anxiety. Interestingly, the increase in top-down connections to sensorimotor cortex were not associated with fear affect scores, thus establishing the (relative) dissociation between somatic and cognitive dimensions of anxiety. Overall, enhanced top-down effective connectivity in sensorimotor cortices emerges as a promising and quantifiable candidate marker of trait somatic anxiety.

Allostatic-Interoceptive Overload in Frontotemporal Dementia

BACKGROUND

The predictive coding theory of allostatic-interoceptive load states that brain networks mediating autonomic regulation and interoceptive-exteroceptive balance regulate the internal milieu to anticipate future needs and environmental demands. These functions seem to be distinctly compromised in behavioral variant frontotemporal dementia (bvFTD), including alterations of the allostatic-interoceptive network (AIN). Here, we hypothesize that bvFTD is typified by an allostatic-interoceptive overload.

METHODS

We assessed resting-state heartbeat evoked potential (rsHEP) modulation as well as its behavioral and multimodal neuroimaging correlates in patients with bvFTD relative to healthy control subjects and patients with Alzheimer's disease (N = 94). We measured 1) resting-state electroencephalography (to assess the rsHEP, prompted by visceral inputs and modulated by internal body sensing), 2) associations between rsHEP and its neural generators (source location), 3) cognitive disturbances (cognitive state, executive functions, facial emotion recognition), 4) brain atrophy, and 5) resting-state functional magnetic resonance imaging functional connectivity (AIN vs. control networks).

RESULTS

Relative to healthy control subjects and patients with Alzheimer's disease, patients with bvFTD presented more negative rsHEP amplitudes with sources in critical hubs of the AIN (insula, amygdala, somatosensory cortex, hippocampus, anterior cingulate cortex). This exacerbated rsHEP modulation selectively predicted the patients' cognitive profile (including cognitive decline, executive dysfunction, and emotional impairments). In addition, increased rsHEP modulation in bvFTD was associated with decreased brain volume and connectivity of the AIN. Machine learning results confirmed AIN specificity in predicting the bvFTD group.

CONCLUSIONS

Altogether, these results suggest that bvFTD may be characterized by an allostatic-interoceptive overload manifested in ongoing electrophysiological markers, brain atrophy, functional networks, and cognition.

Interoception Dysfunction Contributes to the Negative Emotional Bias in Major Depressive Disorder

Background

Previous research studies have demonstrated that impaired interoception is involved in emotional information processing in major depressive disorder (MDD). Heartbeat-evoked potential (HEP) amplitudes, an index for interoception, could be manipulated by emotional faces in healthy people. Considering negative emotional bias is the core characteristic in MDD, we hypothesized that interoception dysfunction was associated with the negative emotional bias in MDD.

Methods

An electroencephalogram (EEG) study under an emotional faces task was applied to explore the relationship between interoception and emotional bias. HEPs before emotional faces stimuli were used to predict the late positive potential (LPP) amplitudes and it worked as an index of emotional bias. Twenty-seven patients with MDD and 27 healthy controls (HCs) participated in this study. Source analysis gave an auxiliary description for results in sensory level.

Results

Major depressive disorders (MDDs) had poor performance in the heartbeat count task (HCT) and attenuate HEP average amplitudes (455-550 ms). Compared with HCs, cluster-based permutation t-tests revealed that MDDs had attenuated LPP amplitudes (300-1,000 ms) over centroparietal regions and enhanced LPP amplitudes over frontocentral regions. Furthermore, abnormal attenuated HEPs could predict aberrant LPPs under sad face stimuli in MDDs, which could be associated with the dysfunction of the anterior cingulate cortex (ACC) and right insula.

Conclusion

Mediated by ACC and insula, interoception dysfunction contributes to the negative emotional bias of MDD, highlighting the importance of interoception in the disorder.

Past and Future Explanations for Depersonalization and Derealization Disorder: A Role for Predictive Coding

Depersonalization (DP) and derealization (DR) refer to states of dissociation in which one feels a sense of alienation in relation to one's self and environment, respectively. Whilst transient episodes often diminish without treatment, chronic experiences of DP and DR may last for years, with common treatments lacking a strong evidence base for their efficacy. We propose a theoretical explanation of DP and DR based on interoceptive predictive coding, and discuss how transient experiences of DP and DR may be induced in the non-clinical population using virtual reality. Further, we review the use of heartbeat evoked potentials in detecting the neural correlates of DP and DR allowing for an objective measure of these experiences in the non-clinical population. Finally, we discuss how the induction and detection of transient experiences of DP and DR in the non-clinical population could shed light on how the brain constructs one's sense of self and reality.

The heartbeat evoked potential is a questionable biomarker in nightmare disorder: A replication study

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Perogamvros et al. (2013) examined heart beat evoked potential (HEP) in nightmare sufferers.

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Increased HEP was proposed to be a robust biomarker in nightmare disorder.

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We aimed to replicate the original study in two separate and larger databases.

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We did not confirm the original finding showing differential HEP in REM sleep.

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Our data cast doubts on the utility of HEP as a biomarker in nightmare disorder.

Frequent nightmares are highly prevalent and constitute a risk factor for a wide range of psychopathological conditions. Despite its prevalence and clinical relevance however, the pathophysiological mechanisms of nightmares are poorly understood. A recent study (Perogamvros et, al 2019) examined the heart beat evoked potential (HEP) in a small group of nightmare sufferers (N = 11) and matched healthy controls (N = 11) and observed markedly different (Hedges’ g = 1.42 [0.62–2.22]) HEP response across the groups during Rapid Eye Movement (REM) sleep. Moreover, the HEP correlated with depression scores in the nightmare group only. The authors concluded that the HEP in REM sleep could be used as a trait-like biomarker reflecting pathological emotional-and sleep regulation in nightmare disorder. To replicate the above study, we performed the same analyses of HEPs in two separate, and larger databases comprising the polysomnographic recordings of nightmare sufferers and matched controls (N_{Study 1} = 39 ; N_{Study 2} = 41). In contrast to the original findings, we did not observe significant differences in HEP across the two groups in either of the two databases. Moreover, we found no associations between depression scores and HEP amplitudes in the relevant spatiotemporal cluster. Our data cast doubts on the utility of HEP as a biomarker in the diagnostic and treatment procedures of nightmare disorder and suggests that the interpretation of HEP as a marker of impaired arousal and emotional processing during REM sleep is premature and requires further validation.

Auricular transcutaneous vagus nerve stimulation modulates the heart-evoked potential

BACKGROUND

There is active interest in biomarker discovery for transcutaneous auricular vagus nerve stimulation (taVNS). However, greater understanding of the neurobiological mechanisms is needed to identify candidate markers. Accumulating evidence suggests that taVNS influences activity in solitary and parabrachial nuclei, the primary brainstem relays for the transmission of visceral sensory afferents to the insula. The insula mediates interoception, which concerns the representation and regulation of homeostatic bodily states. Consequently, interoceptive pathways may be relevant to taVNS mechanisms of action.

HYPOTHESES

We hypothesized that taVNS would modulate an EEG-derived marker of interoceptive processing known as the heart-evoked potential (HEP). We also hypothesized that taVNS-induced HEP effects would be localizable to the insula.

METHODS

Using a within-subject, sham-controlled design in 43 healthy adults, we recorded EEG and ECG concurrent to taVNS. Using ECG and EEG data, we extracted HEPs. Estimation of the cortical sources of the taVNS-dependent HEP responses observed at the scalp were computed using the Boundary Element Method and weighted Minimum Norm Estimation. Statistics were calculated using cluster-based permutation methods.

RESULTS

taVNS altered HEP amplitudes at frontocentral and centroparietal electrode sites at various latencies. The taVNS-dependent HEP effect was localized to the insula, operculum, somatosensory cortex, and orbital and ventromedial prefrontal regions.

CONCLUSION

The results support the hypothesis that taVNS can access the insula as well as functionally and anatomically connected ventral prefrontal regions. HEPs may serve as an objective, non-invasive outcome parameter for the cortical effects of taVNS.

Anti-Heartbeat-Evoked Potentials Performance in Event-Related Potentials-Based Mental Workload Assessment

The aim of this study was to determine the effect of heartbeat-evoked potentials (HEPs) on the performance of an event-related potential (ERP)-based classification of mental workload (MWL). We produced low- and high-MWLs using a mental arithmetic task and measured the ERP response of 14 participants. ERP trials were divided into three conditions based on the effect of HEPs on ERPs: ERP_HEP, containing the heartbeat in a period of 280–700ms in ERP epochs after the target; ERP_A-HEP, not including the heartbeat within the same period; and ERP_T, all trials including ERP_A-HEP and ERP_HEP. We then compared MWL classification performance using the amplitude and latency of the P600 ERP among the three conditions. The ERP_A-HEP condition achieved an accuracy of 100% using a radial basis function-support vector machine (with 10-fold cross-validation), showing an increase of 14.3 and 28.6% in accuracy compared to ERP_T (85.7%) and ERP_HEP (71.4%), respectively. The results suggest that evoked potentials caused by heartbeat overlapped or interfered with the ERPs and weakened the ERP response to stimuli. This study reveals the effect of the evoked potentials induced by heartbeats on the performance of the MWL classification based on ERPs.

Weaker implicit interoception is associated with more negative body image: Evidence from gastric-alpha phase amplitude coupling and the heartbeat evoked potential

Interoception refers to the processing of internal bodily stimuli, while body image refers to appearance-related perceptions, affect, and cognitions. Previous research has found that body image is associated with self-reported and behavioural indices of interoception. Here, we extended this research by examining associations between measures of positive (i.e., body appreciation, functionality appreciation) and negative body image (i.e., body shame, weight preoccupation) and two electrophysiological indices of interoceptive processing, namely the heartbeat evoked potential (HEP) and gastric-alpha phase-amplitude coupling (PAC), in a sample of 36 adults. Significant negative associations were identified between the indices of negative body image and the interoception variables. Specifically, more negative HEP amplitude and lower gastric-alpha PAC were both associated with greater body shame and weight preoccupation. However, no significant associations were identified for the indices of positive body image. These findings extend previous work by demonstrating that there are significant associations between negative body image and previously unexplored components of cardiac and gastric interoception. This, in turn, could have important clinical applications, such as the HEP and gastric-alpha PAC both serving as biomarkers of negative body image.

Out-of-step: brain-heart desynchronization in anxiety disorders

Imaging studies in anxiety disorders (AD) show abnormal functional connectivity primarily in the salience network (SN), somatomotor network (SMN), and default mode network (DMN). However, it is not clear how precisely these network changes occur including their relation to psychopathological symptoms. Here, we show that the functional networks affected in AD overlap with cortical regions that receive visceral inputs (the so-called central/visceral autonomic network). Focusing on cardiac afferents, we suggest that network changes in AD may be due to reduced phase synchronization between ongoing neural and cardiac activity. This neuro-cardiac desynchronization occurs due to the abnormal phase resetting of neural activity at the onset of each heartbeat, as measured by a lower intertrial coherence and heartbeat-evoked potential. Biochemically, cardiac afferents reach subcortical serotonergic raphe nuclei and noradrenergic locus coeruleus (among others) which, in turn, are known to reciprocally modulate the DMN and SMN/SN on the cortical level. Consistent with the network changes in AD, decreases in serotonergic and noradrenergic activity are known to increase connectivity in both SMN and SN while, at the same time, they decrease DMN connectivity. SMN and SN increases, in turn, lead to increased emotional arousal/anxiety and bodily awareness whereas decreased DMN connectivity leads to an unstable sense-of-self in AD. Finally, we integrate our proposal with interoceptive predictive processing models suggesting neuro-cardiac desynchronization as a mechanism for "noisy" bottom-up information leading to a persistently uncertain bodily state in top-down models. In sum, integrating theories on active interference and hyperarousal, we propose a precise neuro-cardiac and biochemically -driven mechanisms for key psychopathological symptoms of AD.

Evidence toward the potential absence of relationship between temporal and spatial heartbeats perception

Many interoceptive tasks (i.e. measuring the sensitivity to bodily signals) are based upon heartbeats perception. However, the temporal perception of heartbeats-when heartbeats are felt-varies among individuals. Moreover, the spatial perception of heartbeats-where on the body heartbeats are felt-has not been characterized in relation to temporal. This study used a multi-interval heartbeat discrimination task in which participants judged the timing of their own heartbeats in relation to external tones. The perception of heartbeats in both time and spatial domains, and relationship between these domains was investigated. Heartbeat perception occurred on average ~ 250 ms after the ECG R-wave, most frequently sampled from the left part of the chest. Participants' confidence in discriminating the timing of heartbeats from external tones was maximal at 0 ms (tone played at R-wave). Higher confidence was related to reduced dispersion of sampling locations, but Bayesian statistics indicated the absence of relationship between temporal and spatial heartbeats perception. Finally, the spatial precision of heartbeat perception was related to state-anxiety scores, yet largely independent of cardiovascular parameters. This investigation of heartbeat perception provides fresh insights concerning interoceptive signals that contribute to emotion, cognition and behaviour.

The manifestation of individual differences in sensitivity to punishment during resting state is modulated by eye state

Structural and functional neuroimaging studies have shown that brain areas associated with fear and anxiety (defensive system areas) are modulated by individual differences in sensitivity to punishment (SP). However, little is known about how SP is related to brain functional connectivity and the factors that modulate this relationship. In this study, we investigated whether a simple methodological manipulation, such as performing a resting state with eyes open or eyes closed, can modulate the manifestation of individual differences in SP. To this end, we performed an exploratory fMRI resting state study in which a group of participants (n = 88) performed a resting state with eyes closed and another group (n = 56) performed a resting state with eyes open. All participants completed the Sensitivity to Punishment and Sensitivity to Reward Questionnaire. Seed-based functional connectivity analyses were performed in the amygdala, hippocampus, and periaqueductal gray (PAG). Our results showed that the relationship between SP and left amygdala-precuneus and left hippocampus-precuneus functional connectivity was modulated by eye state. Moreover, in the eyes open group, SP was negatively related to the functional connectivity between the PAG and amygdala and between the PAG and left hippocampus, and it was positively related to the functional connectivity between the amygdala and hippocampus. Together, our results may suggest underlying differences in the connectivity between anxiety-related areas based on eye state, which in turn would affect the manifestation of individual differences in SP.

The synergistic effect between interoceptive accuracy and alcohol use disorder status on pain sensitivity

BACKGROUND

Interoceptive accuracy and pain sensitivity are both risk factors in the development of alcohol use disorder (AUD). However, the synergistic association between these two factors has not been investigated in an AUD sample. Therefore, the aim of the current study was to investigate whether the association between interoceptive accuracy and sensitivity to pain differed across AUD status.

METHODS

The study group included 165 individuals diagnosed with AUD (88.1% men) and 110 healthy controls (HCs; 74.5% men). Interoceptive accuracy was assessed with the Schandry Task. The Pain Sensitivity Questionnaire was utilized to measure sensitivity to pain. Anxiety, biological sex, and age were included as covariates in a model examining the role of AUD status as a moderator in the association between interoceptive accuracy and pain sensitivity.

RESULTS

A significant interaction was found between interoceptive accuracy and AUD status (b = -4.580, 95% CI = [-8.137, -1.022], p = 0.012, ΔR² = 0.032). Findings indicate that interoceptive accuracy was negatively associated with pain sensitivity among individuals with AUD, while there was a trend for an opposite association among healthy controls.

CONCLUSION

We hypothesize that persistent alcohol drinking may contribute to disruption of the normative association between interoception and pain. Future studies should be conducted to develop knowledge on this association and to investigate its possible therapeutic significance and implications.

Progressive brain structural alterations assessed via causal analysis in patients with generalized anxiety disorder

Accumulating neuroimaging studies implicate widespread brain structural alterations in patients with generalized anxiety disorder (GAD), but little is known regarding the temporal information of these changes and their causal relationships. In this study, a morphometric analysis was performed on T1-weighted structural images, and the progressive changes in the gray matter volume (GMV) in GAD were simulated by dividing the patients into different groups from low illness duration to high illness duration. The duration was defined as the interval between the onset of GAD and the time for magnetic resonance imaging collection. Then, a causal structural covariance network analysis was conducted to describe the causal relationships of the brain structural alterations in GAD. With increased illness duration, the GMV reduction in GAD originated from the subgenual anterior cingulate cortex (sgACC) and propagated to the bilateral ventromedial prefrontal cortex, right dorsomedial prefrontal cortex, left inferior temporal gyrus, and right insula. Intriguingly, the sgACC and the right insula had positive causal effects on each other. Moreover, both sgACC and right insula exhibited positive causal effects on the parietal cortex and negative effects on the posterior cingulate cortex, dorsolateral prefrontal cortex, visual cortex, and temporal lobe. The opposite causal effects were noted on the somatosensory and the ventrolateral prefrontal cortices. In conclusion, patients with GAD show gradual GMV reduction with increasing ilness duration. Furthermore, the causal effects of the sgACC and the right insula GMV reduction with shifts of duration may provide an important new avenue for understanding the pathological anomalies in GAD.

Insula shows abnormal task-evoked and resting-state activity in first-episode drug-naïve generalized anxiety disorder

BACKGROUND

Interoception is associated with neural activity in the insula of healthy humans. On the basis of the somatic symptoms in generalized anxiety disorder (GAD), especially abnormal heartbeat perception, we hypothesized that abnormal activity in the insula was associated with interoceptive awareness in patients with GAD.

METHODS

We investigated the psychological correlates of interoceptive awareness in a sample of 34 patients with first-onset, drug-naïve GAD and 30 healthy controls (HCs). Furthermore, we compared blood oxygenation level-dependent responses between the two groups during a heartbeat perception task to assess task-evoked activity and its relationship with psychological measures. We also examined between-group differences in insular subregions resting-state functional connectivity (rsFC), and its relationship with anxiety severity.

RESULTS

Patients with GAD had significantly higher body perception scores than HCs. They also exhibited greater task-evoked activity in the left anterior insula, left posterior insula, and right anterior insula during interoceptive awareness than HCs. Left anterior insula activity was positively correlated with body awareness in patients with GAD, and rsFC between the left anterior insula and left medial prefrontal gyrus was negatively correlated with somatic anxiety severity.

CONCLUSIONS

Investigating a sample of first-episode, drug-naïve patients, our study demonstrated abnormal interoceptive awareness in patients with GAD and that this was related to abnormal anterior insular activity during both rest and task. These results shed new light on the psychological and neural substrates of somatic symptoms in GAD, and they may serve to establish abnormal interoceptive awareness as a neural and psychological marker of GAD.

Altered heartbeat perception sensitivity associated with brain structural alterations in generalised anxiety disorder

Background

Palpitation is a common complaint in generalised anxiety disorder (GAD). Brain imaging studies have investigated the neural mechanism of heartbeat perception in healthy volunteers. This study explored the neuroanatomical differences of altered heartbeat perception in patients with GAD using structural MRI.

Aims

Based on the strong somatic-interoceptive symptoms in GAD, we explored the regional structural brain abnormalities involved in heartbeat perception in patients with GAD.

Methods

This study was applied to the a priori regions using neuroanatomical theories of heartbeat perception, including the insula, anterior cingulate cortex, supplementary motor area and prefrontal cortex. A total of 19 patients with GAD and 19 healthy control subjects were enrolled. We used the FMRIB Software Library voxel-based morphometry software for estimating the grey matter volume of these regions of interest and analysed the correlation between heartbeat perception sensitivity and the volume of abnormal grey matter.

Results

Patients with GAD showed a significantly decreased volume of grey matter in their left medial prefrontal cortex, right orbital frontal cortex and anterior cingulate cortex. The grey matter volume of the left medial prefrontal cortex negatively correlated with heartbeat perception sensitivity in patients with GAD.

Conclusions

It should be the first study that shows heartbeat perception is associated with brain structure in GAD. Our findings suggest that the frontal region may play an important role in aberrant heartbeat perception processing in patients with GAD, and this may be an underlying mechanism resulting in the abnormal cardiovascular complaints in GAD. This is hypothesised as a ‘top-down’ deficiency, especially in the medial prefrontal cortex. This will provide the foundation for a more targeted region for neuromodulation intervention in the future.

Altered interoception in patients with borderline personality disorder: a study using heartbeat-evoked potentials

BACKGROUND

Patients with borderline personality disorder (BPD) experience difficulties in emotional awareness (alexithymia), and often develop dissociative symptoms, which may reflect broader deficits in interoceptive awareness. Whether this is associated with alterations in cortical processing of interoception is currently unknown.

METHODS

We utilized an electrophysiological marker of interoception, i.e. heartbeat-evoked potentials (HEP), and examined its relationship with electrocardiographic correlates of autonomic nervous system (ANS) functioning (heart rate variability), and with self-report measures of alexithymia, dissociation and borderline symptom severity in patients with BPD.

RESULTS

Individuals with BPD had higher HEP amplitudes over frontal electrodes compared to healthy controls. Sympathetic ANS activity was greater in BPD patients than in controls. Across groups, HEP amplitudes were associated with parasympathetic activity over central electrodes and correlated with alexithymia over frontal electrodes.

CONCLUSIONS

These findings support the idea that difficulties in emotional awareness in BPD are reflected in altered frontal electrophysiological markers of interception. Therefore, emotional awareness can be understood as failures of modulation between interoceptive and exteroceptive attention. Future research may aim to investigate whether altered interoception and its electrophysiological correlates are malleable by therapeutic intervention.