Palpitations in Women With Breast Cancer Are Associated With Polymorphisms for Neurotransmitter Genes.

OBJECTIVES: To evaluate for associations between the occurrence of palpitations reported by women prior to breast cancer surgery and single nucleotide polymorphisms (SNPs) for neurotransmitter genes. SAMPLE & SETTING: A total of 398 women, who were scheduled for unilateral breast cancer surgery, provided detailed information on demographic and clinical characteristics and the occurrence of palpitations prior to breast cancer surgery. METHODS & VARIABLES: The occurrence of palpitations was assessed using a single item (i.e., "heart races/pounds" in the past week ["yes"/"no"]). Blood samples were collected for genomic analyses. Multiple logistic regression analyses were used to identify associations between the occurrence of palpitations and variations in neurotransmitter genes. RESULTS: Nine SNPs and two haplotypes among 11 candidate genes were associated with the occurrence of palpitations. These genes encode for a number of neurotransmitters and/or their receptors, including serotonin, norepinephrine, dopamine, gamma-amino butyric acid, Substance P, and neurokinin. IMPLICATIONS FOR NURSING: These findings suggest that alterations in a variety of neurotransmitters contribute to the development of this symptom.

Somatic symptom distress is not related to cardioceptive accuracy.

OBJECTIVE: (Cardiac) interoception was long considered a key mechanism behind symptom perception in persistent somatic symptoms (PSS). In this study, we aimed to extend earlier findings to clarify this potential interoceptive mechanisms of PSS. METHODS: A cross-sectional sample of 251 participants (23.1% with self-reported functional somatic syndrome) completed a laboratory study with two cardioceptive accuracy tasks (Schandry task and a new cardiac signal detection task) and multiple questionnaires. Somatic symptom distress and associated constructs were assessed with the PHQ-15, as well as with a novel multidimensional questionnaire measure (HiTOP-SF1) derived from the somatoform spectrum of the Hierarchical Taxonomy of Psychopathology (HiTOP). Correlations (frequentist and Bayesian) and structural equation modelling (SEM) helped further investigate the interplay between these variables. RESULTS: There were no significant correlations between measures of interoception and somatic symptom distress. Self-report and behavioral cardioceptive accuracy measures did not correlate significantly. No significant covariances emerged between diagnostic tools and cardioceptive accuracy; Bayesian analyses supported the lack of association between interoception and symptom perception. CONCLUSIONS: Cardiac interoception (specifically cardioceptive accuracy) unlikely represents a key mechanism in PSS etiology. We recommend investigating other factors in PSS.

Heightened interoception in adults with fibromyalgia.

Previous research suggests that the processing of internal body sensations (interoception) affects how we experience pain. Some evidence suggests that people with fibromyalgia syndrome (FMS) - a condition characterised by chronic pain and fatigue - may have altered interoceptive processing. However, extant findings are inconclusive, and some tasks previously used to measure interoception are of questionable validity. Here, we used an alternative measure - the Phase Adjustment Task (PAT) - to examine cardiac interoceptive accuracy in adults with FMS. We examined: (i) the tolerability of the PAT in an FMS sample (N = 154); (ii) if there are differences in facets of interoception (PAT performance, PAT-related confidence, and scores on the Private Body Consciousness Scale) between an FMS sample and an age- and gender-matched pain-free sample (N = 94); and (iii) if subgroups of participants with FMS are identifiable according to interoceptive accuracy levels. We found the PAT was tolerable in the FMS sample, with additional task breaks and a recommended hand posture. The FMS sample were more likely to be classified as 'interoceptive' on the PAT, and had significantly higher self-reported interoception compared to the pain-free sample. Within the FMS sample, we identified a subgroup who demonstrated very strong evidence of being interoceptive, and concurrently had lower fibromyalgia symptom impact (although the effect size was small). Conversely, self-reported interoception was positively correlated with FMS symptom severity and impact. Overall, interoception may be an important factor to consider in understanding and managing FMS symptoms. We recommend future longitudinal work to better understand associations between fluctuating FMS symptoms and interoception.

Reliability of the Heartbeat Tracking Task to Assess Interoception.

Interoception refers to the competence in perceiving and interpreting internal sensations emerging from the body. The most common approach to assess interoception is through cardiac interoceptive tests like the heartbeat tracking task (HTT), which measures the accuracy on perceive and counting heartbeats during a period. However, the literature is scarce in providing adequate reliability evidence for this measure so that the interoception assessment may be threaten. In addition to HTT accuracy, it is possible to determine sensibility (self-reported confidence) and interoceptive awareness (correspondence between accuracy and sensibility). Thus, we measured the test-retest reliability of HTT and also investigated the behavior of HTT outcomes along the task. Therefore, 31 healthy adults (16 males) with 27.8 (9.4) years old performed two consecutive HTT interspersed by one day. Intraclass correlation coefficient (ICC), standard error of measurement (SEM) and minimal detectable difference (MD) analyzes showed 'Good' relative reliability for interoceptive accuracy (ICC = 0.880; SEM = 0.263; MD = 0.728; p < 0.001) and 'Moderate' for sensibility (ICC = 0.617; SEM = 0.648; MD = 1.797; p < 0.001) and awareness (ICC = 0.593; SEM = 0.227; MD = 0.628; p < 0.001). The absolute reliability shows low threshold values for observing true effects in HTT outcomes. The results also showed that reducing the number of HTT blocks did not impact the outcomes. The HTT showed to be reliable in determine the interoceptive competences in healthy adults.

Mediterranean diet, interoception and mental health: Is it time to look beyond the 'Gut-brain axis'?

OBJECTIVE: A Mediterranean style diet (i.e., high in fruit, vegetables, fish, pulses, and wholegrains) is said to benefit psychological health. Many low-level interoceptive processes, such as those involved in the 'gut-brain' axis, are suggested to play a mechanistic role in in this relationship. However, interoceptive sensations in other domains, and at higher hierarchical levels of abstraction, have hitherto been overlooked. One domain often studied in relation to psychological health is cardioception. Therefore, we examined whether the Mediterranean diet was associated with first-order perceptual and second-order metacognitive cardioception. METHODS: Participants completed the Heartbeat Detection Task, the Heartbeat Counting Task, and the EPIC-Norfolk Food Frequency Questionnaire from which diet was quantified. RESULTS: Adherence to a Mediterranean style diet was associated with higher cardioceptive accuracy (i.e., perceptual performance) across both tasks. In addition, those consuming a Mediterranean diet had a better ability to detect errors in first order perceptual performance, and a lower prediction error (the magnitude of the difference between accuracy and confidence). DISCUSSION: These findings indicated that deepening our understanding of how interoceptive processes beyond the 'gut-brain' axis are shaped by diet could deepen our understanding of the link between diet and mental health and wellbeing.

Interoception during aging: Functional neuroimaging data from a heartbeat detection task.

Interoception is critically important for allostatic adaptation and emotional regulation, and aberrant interoceptive processing is increasingly recognized to be involved in the pathogenesis of neurological, psychiatric and cardiovascular diseases. Despite the fact that interoceptive abilities decline with age, the corresponding neural correlates and clinical consequences of these age-related changes have yet to be discovered. We present a dataset that contains task-based functional neuroimaging data from 50 adults aged 40-65 years and 12 adults aged 18-25 years who performed an fMRI-based heartbeat-detection task. Of the 62, 38 participants also took part in a rubber hand illusion experiment outside the scanner. While the dataset was mainly created to study age-related changes in interoception, it can also be used in body perception research in general. The provided group data may serve as a reference for clinical studies on interoception involving older adults.

An Embodied Cognition Perspective on the Role of Interoception in the Development of the Minimal Self.

Interoception is an often neglected but crucial aspect of the human minimal self. In this perspective, we extend the embodiment account of interoceptive inference to explain the development of the minimal self in humans. To do so, we first provide a comparative overview of the central accounts addressing the link between interoception and the minimal self. Grounding our arguments on the embodiment framework, we propose a bidirectional relationship between motor and interoceptive states, which jointly contribute to the development of the minimal self. We present empirical findings on interoception in development and discuss the role of interoception in the development of the minimal self. Moreover, we make theoretical predictions that can be tested in future experiments. Our goal is to provide a comprehensive view on the mechanisms underlying the minimal self by explaining the role of interoception in the development of the minimal self.

Measuring Interoception: The CARdiac Elevation Detection Task.

Interoception has increasingly been the focus of psychiatric research, due to its hypothesized role in mental health. Existing interoceptive tasks either suffer from important methodological limitations, impacting their validity, or are burdensome and require specialized equipment, which limits their usage in vulnerable populations. We report on the development of the CARdiac Elevation Detection (CARED) task. Participants' heart rate is recorded by a wearable device connected to a mobile application. Notifications are sent to participants' mobile throughout the day over a period of 4 weeks. Participants are asked to state whether their heart rate is higher than usual, rate their confidence and describe the activity they were involved in when the notification occurred. Data (N = 30) revealed that 1/3 of the sample was classified as interoceptive and that participants presented overall good insight into their interoceptive abilities. Given its ease of administration and accessibility, the CARED task has the potential to be a significant asset for psychiatric and developmental research.

Measuring interoception: The phase adjustment task.

Interoception, perception of one's bodily state, has been associated with mental health and socio-emotional processes. However, several interoception tasks are of questionable validity, meaning associations between interoception and other variables require confirmation with new measures. Here we describe the novel, smartphone-based Phase Adjustment Task (PAT). Tones are presented at the participant's heart rate, but out of phase with heartbeats. Participants adjust the phase relationship between tones and heartbeats until they are synchronous. Data from 124 participants indicates variance in performance across participants which is not affected by physiological or strategic confounds. Associations between interoception and anxiety, depression and stress were not significant. Weak associations between interoception and mental health variables may be a consequence of testing a non-clinical sample. A second study revealed PAT performance to be moderately stable over one week, consistent with state effects on interoception.

The effects of vibrotactile masking on heartbeat detection: Evidence that somatosensory mechanoreceptors transduce heartbeat sensations.

The ability to detect heartbeat sensations is the most common basis for inferring individual differences in sensitivity to the interoceptive stimuli generated by the visceral activity. While the sensory sources of heartbeat sensations have yet to be identified, there is a growing consensus that visceral sensation, in general, is supported not only by the interoceptive system but also by the somatosensory system, and even by exteroception. The current experiment sought evidence on this issue by exploring the effects of masking the functions of somatosensory Pacinian and non-Pacinian mechanoreceptors on the ability to detect heartbeat sensations. Twelve verified heartbeat detectors completed a multi-session experiment in which they judged heartbeat-tone and light-tone simultaneity under two vibrotactile masking conditions involving the stimulation of the sternum: (a) using 250 Hz vibrotactile stimuli to mask the Pacinian channel, and (b) using 6 Hz vibrotactile stimuli to mask the non-Pacinian channel. A no-vibration control condition in which no masking stimuli were presented was also implemented. Presentation of both the 250 Hz and the 6 Hz masking stimuli impaired the ability to judge the simultaneity of heartbeats and tones but did not influence the ability to judge the simultaneity of stimuli presented to different exteroceptive modalities (lights and tones). Our findings reinforce the view that the somatosensory system is involved in cardioception and support the conclusion that both Pacinian and non-Pacinian somatosensory mechanoreceptors are implicated in heartbeat detection.

Cardiac and Proprioceptive Accuracy Are Not Related to Body Awareness, Perceived Body Competence, and Affect.

Interoception in the broader sense refers to the perception of internal states, including the perception of the actual state of the internal organs (visceroception) and the motor system (proprioception). Dimensions of interoception include (1) interoceptive accuracy, i.e., the ability to sense internal changes assessed with behavioral tests, (2) confidence rating with respect to perceived performance in an actual behavioral test, and (3) interoceptive sensibility, i.e., the self-reported generalized ability to perceive body changes. The relationship between dimension of cardioceptive and proprioceptive modalities and their association with affect are scarcely studied. In the present study, undergraduate students (N = 105, 53 males, age: 21.0 ± 1.87 years) filled out questionnaires assessing positive and negative affect (Positive and Negative Affect Schedule), interoceptive sensibility (Body Awareness Questionnaire), and body competence (Body Competence Scale of the Body Consciousness Questionnaire). Following this, they completed a behavioral task assessing cardioceptive accuracy (the mental heartbeat tracking task by Schandry) and two tasks assessing proprioceptive accuracy with respect to the tension of arm flexor muscles (weight discrimination task) and the angular position of the elbow joint (joint position reproduction task). Confidence ratings were measured with visual analog scales after the tasks. With the exception of a weak association between cardioceptive accuracy and the respective confidence rating, no associations between and within modalities were found with respect to various dimensions of interoception. Further, the interoceptive dimensions were not associated with state and trait positive and negative affect and perceived body competence. In summary, interoceptive accuracy scores do not substantially contribute to conscious representations of cardioceptive and proprioceptive ability. Within our data, non-pathological affective states (PANAS) are not associated with the major dimensions of interoception for the cardiac and proprioceptive modalities.

The effects of alcohol on heartbeat perception: Implications for anxiety.

INTRODUCTION: It is well established that some individuals self-medicate their anxiety with alcohol. Though much evidence exists that alcohol consumption can be negatively reinforcing, there remains uncertainty regarding what mediates the relationship between alcohol and anxiety. An unexplored possibility is that, for some, alcohol impairs interoceptive sensitivity (the ability to accurately perceive one's physiological state), thereby decreasing state anxiety. Consistent with this, highly accurate heartbeat perception is a risk factor both for elevated trait anxiety and anxiety disorders. However, the direct impact of alcohol on cardioceptive accuracy has not to our knowledge been previously examined. METHODS: Sixty-one social drinkers came to the lab in groups of 4-6 on two days spaced a week apart. Each participant was randomly assigned to receive alcoholic drinks targeting a BAC of 0.05% on one testing day and placebo drinks on the other, with the order counter-balanced. On both testing days, participants engaged in a Schandry heartbeat perception task on three occasions: at baseline, after an alcohol absorption period, and after physiological arousal was raised via exercise. RESULTS: For men only, alcohol significantly impaired cardioceptive accuracy relative to a placebo at both low and high levels of arousal, with medium to large effect sizes. CONCLUSIONS: Though preliminary, this finding is consistent with the proposed hypothesis linking alcohol consumption and anxiety, at least for men. Future studies should directly examine whether, among individuals with anxiety disorders, cardioceptive sensitivity mediates the relationship between alcohol consumption and state anxiety.

Neural correlates of heart-focused interoception: a functional magnetic resonance imaging meta-analysis.

Interoception is the ability to perceive one's internal body state including visceral sensations. Heart-focused interoception has received particular attention, in part due to a readily available task for behavioural assessment, but also due to accumulating evidence for a significant role in emotional experience, decision-making and clinical disorders such as anxiety and depression. Improved understanding of the underlying neural correlates is important to promote development of anatomical-functional models and suitable intervention strategies. In the present meta-analysis, nine studies reporting neural activity associated with interoceptive attentiveness (i.e. focused attention to a particular interoceptive signal for a given time interval) to one's heartbeat were submitted to a multilevel kernel density analysis. The findings corroborated an extended network associated with heart-focused interoceptive attentiveness including the posterior right and left insula, right claustrum, precentral gyrus and medial frontal gyrus. Right-hemispheric dominance emphasizes non-verbal information processing with the posterior insula presumably serving as the major gateway for cardioception. Prefrontal neural activity may reflect both top-down attention deployment and processing of feed-forward cardioceptive information, possibly orchestrated via the claustrum.This article is part of the themed issue 'Interoception beyond homeostasis: affect, cognition and mental health'.