Neural Responses to Heartbeats in the Default Network Encode the Self in Spontaneous Thoughts

The default network (DN) has been consistently associated with self-related cognition, but also to bodily state monitoring and autonomic regulation. We hypothesized that these two seemingly disparate functional roles of the DN are functionally coupled, in line with theories proposing that selfhood is grounded in the neural monitoring of internal organs, such as the heart. We measured with magnetoencephalograhy neural responses evoked by heartbeats while human participants freely mind-wandered. When interrupted by a visual stimulus at random intervals, participants scored the self-relatedness of the interrupted thought. They evaluated their involvement as the first-person perspective subject or agent in the thought (“I”), and on another scale to what degree they were thinking about themselves (“Me”). During the interrupted thought, neural responses to heartbeats in two regions of the DN, the ventral precuneus and the ventromedial prefrontal cortex, covaried, respectively, with the “I” and the “Me” dimensions of the self, even at the single-trial level. No covariation between self-relatedness and peripheral autonomic measures (heart rate, heart rate variability, pupil diameter, electrodermal activity, respiration rate, and phase) or alpha power was observed. Our results reveal a direct link between selfhood and neural responses to heartbeats in the DN and thus directly support theories grounding selfhood in the neural monitoring of visceral inputs. More generally, the tight functional coupling between self-related processing and cardiac monitoring observed here implies that, even in the absence of measured changes in peripheral bodily measures, physiological and cognitive functions have to be considered jointly in the DN

Heart Is Deceitful Above All Things : Threat Expectancy Induces the Illusory Perception of Increased Heartrate

The work was funded by Leverhulme Trust grant RPG-2019-248 to PB, and PhD studentship was awarded to EP from the Universities of Plymouth and Aberdeen. This work was also supported by the “Departments of Excellence 2023–2027” initiative of the Italian Ministry of University and Research for the Department of Neuroscience, Imaging and Clinical Sciences (DNISC) of the University of Chieti-Pescara, and by the “Search for Excellence” initiative of the University of Chieti-Pescar to FF. The research was also supported by EU - NextGenerationEU - MUR-Fondo Promozione e Sviluppo - DM 737/2021; Project: INTRIGUE, Interoception and Fatigue: predicting and treating pathological and transient fatigue to MC.Peer reviewedPostprin

The role of interoception in cognition, and its application to autism spectrum disorders

Traditionally a distinction was drawn between cognitive and sensorimotor processes, with little consideration of communication between the two. However, many findings are incompatible with this separation (e.g. Lebedev & Wise, 2002; Patel, Fleming & Kilner, 2012). One particular domain where this is evidenced is interoception. Interoception has been defined as the sensing of the physiological condition of the body (Craig, 2002). While it has long been clear that interoception is of fundamental importance for homeostasis, it is increasingly being recognised as integral for multiple domains of cognition, including emotion. For example, those with greater access to their interoceptive states experience emotions more intensely (e.g. Wiens, Mezzacappa, & Katkin, 2000). These findings bare on our understanding of autism. For some time, exteroceptive sensory abnormalities has been recognised in autism, with such symptoms now included in the diagnostic criteria. Far less research has considered how interoception is implicated in autism. The reports of autistic people and their caregivers, in addition to a few empirical investigations, suggest that interoceptive processing is altered in autism. It is therefore possible that these interoceptive alterations are implicated in the cognitive symptoms of autism. In this PhD I conducted a series of experiments to test the hypothesis that afferent signals from the body, including interoceptive sensations, are involved in cognition, and that the processing of these signals is altered in autism. More specifically, I tested the role of bodily afferents in metacognition, movement, anxiety, and emotion. I also sought to determine if there are interoceptive differences in the three domains of interoception delineated by Garfinkel and colleagues (Garfinkel & Critchley, 2013; Garfinkel, Seth, Barrett, Suzuki, & Critchley, 2015) in autistic children and adolescents, having previously only been evaluated previously in autistic adults. Finally, I investigated whether differences in emotion processing in autism were related to interoception

Symptoms of depersonalisation/derealisation disorder as measured by brain electrical activity: A systematic review

Depersonalisation/derealisation disorder (DPD) refers to frequent and persistent detachment from bodily self and disengagement from the outside world. As a dissociative disorder, DPD affects 1–2 % of the population, but takes 7–12 years on average to be accurately diagnosed. In this systematic review, we comprehensively describe research targeting the neural correlates of core DPD symptoms, covering publications between 1992 and 2020 that have used electrophysiological techniques. The aim was to investigate the diagnostic potential of these relatively inexpensive and convenient neuroimaging tools. We review the EEG power spectrum, components of the event-related potential (ERP), as well as vestibular and heartbeat evoked potentials as likely electrophysiological biomarkers to study DPD symptoms. We argue that acute anxiety- or trauma-related impairments in the integration of interoceptive and exteroceptive signals play a key role in the formation of DPD symptoms, and that future research needs analysis methods that can take this integration into account. We suggest tools for prospective studies of electrophysiological DPD biomarkers, which are urgently needed to fully develop their diagnostic potential

Emotion matters: Different psychophysiological responses to expressive and non-expressive full-body movements

We explore dance video clip stimuli as a means to test human observers' accuracy in detecting genuine emotional expressivity in full-body movements. Stimuli of every-day-type full-body expressions of emotions usually use culturally very recognizable actions (e.g. fist shaking for anger, etc). However, expressive dance movement stimuli can be created to contain fully abstract movements. The expressivity results from subtle variations in the body movements of the expressor, and emotions cannot be recognised by observers via particular actions (e.g. fist shaking, etc). Forty-one participants watched and rated 24 pairs of short dance videos –from a published normalised dance stimuli library– in randomised order (N = 48). Of each carefully matched pair, one version of the full-body movement sequence had been danced to be emotionally genuinely expressive (clip a), while the other version of the same sequence (clip b) had been danced –while technically correct– without any emotional expressivity. Participants rated (i) expressivity (to test their accuracy; block 1), and (ii) how much they liked each movement (an implicit measure to test their emotional response (“liking”); block 2). Participants rated clips that were intended to be expressive as more expressive (part 1: expressivity ratings), and liked those expressive clips more than the non-expressive clips (part 2: liking ratings). Besides, their galvanic skin response differed, depending on the category of clips they were watching (expressive vs. non-expressive), and this relationship was modulated by interceptive accuracy and arts experience. Results are discussed in relation to the Body Precision Hypothesis and the Hypothesis of Constructed Emotion

Neural correlates of conscious and unconscious somatosensory processing

Every day there are somatosensory stimuli on our skin that we perceive one moment and the next not, despite their unchanged physical presence (e.g., insects, wind, clothing). Yet, which are the physiological determinants and neural correlates that accompany external stimuli to enter consciousness or not? To address this question and inform theories of consciousness, this dissertation presents three empirical studies that used weak electrical finger-nerve stimulation which led - despite being physically identical - to subjective experiences of stimulus presence and absence. The first two studies investigated the interaction of tactile conscious perception with two dominant body rhythms: the cardiac and respiratory cycle. The third study investigated the configuration of neural networks being involved in this near-threshold phenomenon. Tactile conscious perception changed over the course of the cardiac cycle (increased detection during diastole) and respiration was tuned such that stimuli occurred more likely during late inspiration / early expiration, resulting in increased detection during early expiration. On the neural level, conscious perception was accompanied by global broadcasting of sensory content across the brain without substantial reconfiguration of the whole-brain functional network in terms of graph metrics. The cardiac cycle effect on conscious tactile perception is a result of cognitive processes which model and predict our body’s internal state to inform perception and guide behavior (e.g., tuning respiration). This perceptual integration of interoceptive and exteroceptive 'beliefs' is also an explanation for widely distributed brain activity differences without whole-brain functional network changes when a tactile stimulus is perceived

Neural-heart interactions in the healthy and injured brain

Introduction Integrating internal and external signals is fundamental for perceiving and interacting with the world via the body. In particular, interoceptive predictive coding frameworks describe these integrated mechanisms as vital for embodied selfhood, emotional experience, and a unified first-person perspective. By definition, a disorder of consciousness patient has dysfunctional awareness of their self and their environment. Despite the dual diagnostic criteria, research has focused almost exclusively on external perceptual awareness, leaving internal self-related aspects of awareness largely unexplored. Thus, we sought to detect neural markers of self-related interoceptive processing with the aim that their detection may predict the recovery of self-awareness in acute unresponsive disorders of consciousness. Experiment one First, we aimed to identify neural markers of interoceptive (i.e., cardiac) and exteroceptive (i.e., auditory) integration in healthy individuals. We presented sequences of sounds at a short delay (i.e., perceived synchronous) or long delay (i.e., perceived asynchronous) from the heartbeat, with half the trials including an omission. We analysed heart-evoked potentials (i.e., HEPs) during omissions to measure pure predictive mechanisms without contaminating auditory responses. Pre-omission HEP responses differed across short delay and long delay trials, potentially reflecting differences in heartbeat-driven expectations of sounds. Furthermore, attending to internal heartbeat sensations modulated omission-evoked responses, supporting the role of attentional-precision in regulating cross-modal predictive mechanisms (i.e., state precision). However, we did not observe modulation of HEP/omission-evoked responses by individual difference in interoceptive ability, which doesn't support the proposed regulating role of trait precision in predictive coding frameworks. Therefore, HEP mechanisms of interoceptive and exteroceptive integration operate partially under interoceptive predictive coding. However, we observed inconsistent evidence of modulation by precision-weighting. Experiment two Second, we sought to determine whether the lack of observed trait precision modulation (i.e., by interoceptive ability) and, therefore, inconsistency with precision- weighting resulted from individual differences in the perceived timing of heartbeat sensations. Thus, in experiment two, we tailored the perceived synchronous cardio-audio delays to each individual to test the influence of trait precision more sensitively. Despite this, we observed no significant modulation of HEPs by state or trait precision. Nonetheless, we replicated the robust HEP effect indicative of cardio-audio expectation. Thus, overall, our findings are inconsistent with a precision-weighted predictive coding view. However, it could be that participants relied less on attentional/state precision under a more individually-tailored task. Furthermore, assessing interoceptive ability is challenging, and thus, our interoceptive performance measures may not accurately reflect trait precision. Experiment three Finally, cortical processing of heartbeats at rest is thought to index self-related aspects of awareness, such as embodied selfhood and the formation of a first-person perspective. Hence, we investigated the prognostic potential of resting HEPs and cardiac measures in acute unresponsive patients. We observed no convincing evidence of HEPs or cardiac measures predicting recovery from acute unresponsiveness, three or six months post-assessment. This lack of evidence suggests resting HEPs are not useful for consciousness prognoses. However, greater prognostic value may be found in HEPs during high-level self-processing or interoceptive-exteroceptive integration (i.e., Experiments one and two). Discussion In summary, we observed robust HEP evidence of interoceptive signals guiding expectations of exteroceptive stimuli. However, we observed inconsistent evidence of modulation of HEPs by state precision and no evidence of modulation by trait precision. Thus, we need more explicit definitions of the manipulation and measurement of precision in predictive coding frameworks to test their influence on interoceptive predictive mechanisms accurately. Finally, although previous evidence indicated the diagnostic value of HEPs, we observed no convincing evidence of their prognostic potential. It is possible that during rest, self-cognitive mechanisms reflected in HEPs are reduced. Therefore, investigating HEPs during tasks involving high-level self-processing or interoceptive-exteroceptive integration may be more valuable for awareness prognoses

Sex differences in interoceptive accuracy:A meta-analysis

Interoceptive accuracy, the ability to correctly perceive internal signals arising from the body, is thought to be disrupted in numerous mental and physical health conditions. Whilst evidence suggests poorer interoceptive accuracy in females compared to males, raising the possibility that interoceptive differences may relate to sex differences in mental and physical health, results concerning sex differences in interoceptive accuracy are mixed. Given such ambiguity, this meta-analysis aimed to establish the presence or absence of sex differences in interoceptive accuracy across cardiac, respiratory, and gastric domains. A review of 7956 abstracts resulted in 93 eligible studies. Results demonstrated superior accuracy in males across cardiac, but not gastric, tasks, while findings on respiratory tasks were mixed. Effect sizes were consistent across cardiac tasks, but instability and/or moderate heterogeneity was observed across other domains, likely due to the small number of eligible studies. Despite such limitations, results indicate the possibility of sex differences across interoception tasks and domains. Methodological limitations concerning the influence of physiological factors, and directions for future research are discussed

Impact of hypnosis on psychophysiological measures: A scoping literature review.

Exploring psychophysiological changes during hypnosis can help to better understand the nature and extent of the hypnotic phenomenon by characterizing its influence on the autonomic nervous system (ANS), in addition to its central brain effects. Hypnosis is thought to induce a relaxation response, yet studies using objective psychophysiological measures alongside hypnosis protocols show various results. We review this literature and clarify the effects of hypnosis on psychophysiological indices of ANS activity and more specifically of the stress/relaxation response, such as heart rate variability and electrodermal activity. Studies reporting psychophysical measures during hypnosis were identified by a series of Pubmed searches. Data was extracted with an interest for the influence of hypnotizability and effects of specific suggestions or tasks on the findings. We found 49 studies comprising 1315 participants, 45 concerning healthy volunteers and only 4 on patients. Sixteen compared high vs. low hypnotizable people; 30 measured heart rate, 18 measured heart rate variability, 25 electrodermal activity, and 23 respiratory signals as well as other physiological parameters. Globally, results converge to show reductions in sympathetic responses and/or increases in parasympathetic tone under hypnosis. Several methodological limitations are underscored, such as older studies (N = 16) using manual analyses, small sample sizes (<30, N = 31), as well as uncontrolled multiple comparisons. Nevertheless, we confirm that hypnosis leads to a physiological relaxation response and highlight promising avenues for this research. Suggestions are made for guiding future work in this field