Cardiovascular mechanisms of interoceptive awareness: Effects of resonance breathing

Association between individual differences in interoception and cardiac coherence during heart rate variability biofeedback

Heart rate variability biofeedback (HRVBF) is the training to increase vagally-mediated heart rate variability (vmHRV), accompanied by slow-paced breathing and feedback of heart rhythm. It has been reported to be effective for emotion and cognition. In recent years, increased attention has turned toward participant characteristics as factors affecting HRVBF training effects. Focusing on neural basis commonalities between the mechanisms of HRVBF training effects and processing interoception, this study comprehensively measured interoception and examined the relationship between interoception and cardiac coherence reflecting HRVBF effects. Fifty-four healthy young participants were recruited, and subjective interoception was measured using the Japanese version of Multidimensional Assessment of Interoceptive Awareness (MAIA-J) and the Japanese version of the Body Perception Questionnaire-Body Awareness Very Short Form (BPQ-BAVSF-J), objective interoception using heartbeat counting task (HCT), heart rate variability (HRV), visual exteroception, and the coherence score achieved by HRVBF. We conducted a multiple regression analysis with interoception, HRV, and visual exteroception parameters as explanatory variables and the coherence score as the objective variable. Some subjective interoception and HRV parameters were found to be associated with the coherence score. Our results were consistent with previous studies, showing that higher vmHRV was related to high cardiac coherence. Interoception effects on cardiac coherence may be limited because of the low adjusted coefficient of determination and less selected explanatory variables in the multiple regression analysis. Our results may contribute toward predicting HRVBF training effects and the screening of those who are likely to benefit from the training from the perspective of interoception and vmHRV.

Predicting fluctuations in cardiac interoceptive accuracy and sensibility through additional heart rate variability reductions in everyday life

Cardiac interoception, assessed in terms of accuracy (IAcc) and sensibility (IS; beside others), is important for health and wellbeing. Ecological momentary assessment studies exploring the dynamics of cardiac interoception showed substantial fluctuations of IAcc and IS in everyday life. States of increased (physiologically indicated) stress, such as decreased heart rate variability (HRV), may hamper interoceptive skills, while more relaxed states (higher HRV) seem to go along with increased IAcc. We built on this and investigated if higher (physiological) stress indicated via HRV reductions independent of metabolic needs (i.e., additional HRV reduction, AddHRVr) could (differentially) predict IAcc and IS, respectively. In an initial sample of 119 participants, with data of (up to) three consecutive days, we simulated the predictive value of AddHRVr. We found that AddHRVr before an ambulatory cardiac interoception task predicted poor IAcc and higher IS. We replicated this pattern of findings in an independent sample of 66 participants. Both studies provide first insights into the dynamics of IAcc and IS in daily life, which seems to differ when following AddHRVr. This lays the groundwork for just in time adaptive interventions (JITAIs) supporting individuals in states of high vulnerability and promoting cardiac interoceptive skills.

Interoception and aging

Interoception refers to the body's perception and regulation of internal physiological states and involves complex neural mechanisms and sensory systems. The current definition of interoception falls short of capturing the breadth of related research; here, we propose an updated definition. Homeostasis, a foundational principle of integrated physiology, is the process by which organisms dynamically maintain optimal balance across all conditions through neural, endocrine, and behavioral functions. This review examines the role of interoception in body homeostasis. Aging is a complex process influenced by multiple factors and involving multiple levels, including physical, psychological, and cognitive. However, interoceptive and aging interoceptive interactions are lacking. A new perspective on interoception and aging holds significant implications for understanding how aging regulates interoception and how interoception affects the aging process. Finally, we summarize that arachidonic acid metabolites show promise as biomarkers of interoception-aging. The aim of this study is to comprehensively analyze interoceptive-aging interactions, understand the aging mechanism from a novel perspective, and provide a theoretical basis for exploring anti-aging strategies.

The Effects of Resonance Frequency Breathing on Cardiovascular System and Brain-Cardiopulmonary Interactions

Resonance frequency (RF) is characterized as the specific frequency at which a system, equipped with delayed self-correction or negative feedback mechanisms, exhibits maximal amplitude oscillations in response to an external stimulus of a particular frequency. Emerging evidence suggests that the cardiovascular system has an inherent RF, and that breathing at this frequency can markedly enhance health and cardiovascular function. However, the efficacy of resonance frequency breathing (RFB) and the specific responses of the cardiovascular, respiratory, and central nervous systems during RFB remain unclear. In this study, we recruited 27 healthy young male subjects (aged 20-30 years) and used the corrected sliding method to accurately determine each subject's RF. We then investigated cardiovascular activity, cardiorespiratory coupling, and the brain-cardiovascular network to clarify the effects and mechanisms associated with RFB. Our results indicate that: (a) the corrected sliding method can precisely evaluate RF; (b) the reduction in blood pressure is unique to RFB and not observed in other slow-paced breathing patterns (RF + 1 and 6 breaths per minute), which we attribute to the α-wave and parasympathetic-BRS pathway; (c) during slow-paced breathing, cardiorespiratory coupling predominantly favors the respiration-to-heart direction, with the RF stage eliciting the most significant response, while brain-cardiopulmonary information transfer increases across all tasks. These findings offer valuable insights into the impact of RFB on the cardiovascular, respiratory, and central nervous systems, potentially laying the groundwork for future research to optimize respiratory training protocols and improve health outcomes.

Cannabidiol alters psychophysiological, craving and anxiety responses in an alcohol cue reactivity task: A cross-over randomized controlled trial

BACKGROUND

Preclinical studies have demonstrated that cannabidiol (CBD) reduces alcohol-seeking behaviors and may have potential for managing alcohol use disorder (AUD). In this study, we examined the effects of CBD versus placebo on (i) psychophysiological, craving and anxiety responses to alcohol and appetitive cues; (ii) tolerability measures including cognitive functioning.

METHODS

Twenty-two non-treatment-seeking individuals with AUD (DSM-5) participated in a cross-over, double-blind, randomized trial, receiving either 800 mg of CBD or matched placebo over 3 days. A laboratory alcohol cue reactivity task with appetitive control (juice) and alcohol exposures, and subsequent recovery periods to examine regulation of cue-elicited responses after cue-offset (recovery) was completed, with psychophysiological indices of autonomic nervous system activity (skin conductance, high-frequency heart rate variability [HF-HRV]) and self-reported measures (alcohol craving and anxiety). Self-reported scales of sedation and neuropsychological executive function tasks were also completed.

RESULTS

CBD sessions were significantly associated with elevated parasympathetic nervous system (PNS) activity across the task, as indicated by increased HF-HRV. Reductions in self-reported anxiety during cue exposure stages compared to placebo sessions were also evidenced. Reductions in self-reported alcohol craving after cue exposure were seen during CBD sessions only. There were no significant differences between CBD and placebo on executive functioning performance.

CONCLUSIONS

In a short-term regimen, CBD appears to modulate PNS activity, reduce cue-elicited anxiety during cue exposure and reduce alcohol craving after cue exposure while not significantly impairing cognition. Large, parallel clinical trials with longer term regimens are now needed to determine the therapeutic potential of CBD in the management of AUD.

Neuroception of safety is associated with elevated heart rate variability in the laboratory and more frequent heart rate variability increases in everyday life

OBJECTIVE

Feeling comfortable and safe has been discussed to foster health and well-being. However, the pathways to better health are complex, involving both behavioral and physiological routes.

METHODS

In this study, we examined the role of safety perception for cardiac health by (1) examining associations with baseline heart rate variability (HRV; Study 1) and (2) evaluating a novel measure of autonomic cardiac flexibility in daily life, namely increases in HRV independent of metabolic demands (ImdHRVi; Study 2).

RESULTS

Study 1 (N = 76) found evidence for a positive association between vagally mediated HRV and the Neuroception of Psychological Safety scale (Morton L, Cogan N, Kolacz J, et al. "A new measure of feeling safe: developing psychometric properties of the Neuroception of Psychological Safety Scale (NPSS)": Correction. Psychol Trauma. 2022; https://doi.org/10.1037/tra0001374), thus suggesting a link between safety and cardiac vagal regulation. In Study 2, a sample of N = 245 adult volunteers participated in a four-day-ambulatory assessment measuring HRV and bodily movement. A regression was calculated between HRV and bodily movement for 12 h of the first recording day, which was then used to calculate minute-by-minute ImdHRVi (beyond those predicted by bodily movement) in the following days. It turned out that safety perception predicted more episodes of ImdHRVi in everyday life, even after controlling for several confounds.

CONCLUSIONS

Findings suggest that feeling safe and everyday life cardiac autonomic regulation are interrelated, thus possibly contributing to adaptive adjustment and health.

Effects of Heart Rate Variability Biofeedback Training on Anxiety Reduction and Brain Activity: a Randomized Active-Controlled Study Using EEG

Heart rate variability biofeedback (HRVBF) is a promising anxiety-reducing intervention that increases vagally-mediated heart rate variability (vmHRV) through slow-paced breathing and feedback of heart rhythm. Several studies have reported the anxiety-reducing effects of HRVBF; however, some studies have reported such training as ineffective. Furthermore, the effects of training and underlying brain activity changes remain unclear. This study examined the anxiety-reducing effects of HRVBF training and related brain activity changes by randomly assigning participants, employing an active control group, and measuring anxiety-related attentional bias using the emotional Stroop task and electroencephalography (EEG). Fifty-five healthy students with anxiety were randomly assigned to the HRVBF or control groups, and 21 in the HRVBF group and 19 in the control group were included in the analysis. Both groups performed 10 training sessions of 20 min each within 3 weeks. They were assessed using resting vmHRV, event-related potential (ERP), time-frequency EEG, attentional bias, and the State-Trait Anxiety Inventory-JYZ (STAI-JYZ) before and after training. The results demonstrated increased resting vmHRV in the HRVBF group compared to the control group after training. However, no differences were observed in ERP, time-frequency EEG, attentional bias, and STAI-JYZ. Participants with higher pre-training resting vmHRV achieved higher heart rhythm coherence in HRVBF training and had reduced attentional bias. This study suggests that individuals with higher resting vmHRV are more likely to be proficient in HRVBF training and benefit from its anxiety-reducing effects. The findings contribute to participant selection to benefit from HRVBF training and modification of the training protocols for non-responders.Clinical trial registrationOrganization: University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR), JapanRegistration number: UMIN000047096Registration date: March 6, 2022.

Limited evidence that alcohol affects emotional face processing via interoceptive pathways, a registered report

BACKGROUND

Our brain uses interoceptive signals from the body to shape how we perceive emotions in others; however, whether interoceptive signals can be manipulated to alter emotional perceptions is unknown. This registered report examined whether alcohol administration triggers physiological changes that alter interoceptive signals and manipulate emotional face processing.

METHODS

Participants (n=36) were administered an alcohol or placebo beverage. Cardiovascular physiology (Heartrate variability, HRD) was recorded before and after administration. Participants completed a behavioral task in which emotional faces were presented in synchrony with different phases of the cardiac cycle (i.e., systole/diastole) to index of how interoceptive signals amplify them.

HYPOTHESES

We hypothesized that alcohol administration would disrupt the cardiac amplification of emotional face processing. We further explored whether this disruption depended on the nature and magnitude of changes in cardiovascular physiology after alcohol administration.

RESULTS

We observed no main effects or interactions between alcohol administration and emotional face processing. We found that HRV at baseline negatively correlated with the cardiac amplification of emotional faces. The extent to which alcohol impacted HRV negatively correlated with the cardiac amplification of angry faces.

CONCLUSIONS

This registered report failed to validate the primary hypotheses but offers some evidence that the effects of alcohol on emotional face processing, if any, could be mediated via changes in basic physiological signals that are integrated via interoceptive mechanisms. Results are interpreted within the context of interoceptive inference and could feed novel perspectives for the interplay between physiological sensitivity and interoception in the development of drug-related behaviors.

Autonomic and cognitive control in memory: Investigating the psychophysiological link using heart rate variability biofeedback

Vagally mediated heart rate variability (vmHRV) at resting state has been associated to cognitive functions dependent on cognitive control, such as memory. However, little is known about the phasic interaction between cognitive and autonomic control. In a pre-registered within-between-subject designed experiment, the potential of vmHRV biofeedback to simultaneously stimulate vmHRV during memory processing and cognitive control over long-term memory was tested, along with investigating psychophysiological association. 71 young healthy adults completed (twice) a false memory task in virtual reality. Immediately before memory encoding and retrieval, participants practiced either vmHRV biofeedback or a control breathing exercise. Cognitive control over long-term memory was assessed as the confidence toward false memories and the capability to discriminate them from true memories. Resting-state vmHRV before each test and phasic vmHRV during memory encoding and retrieval were measured as the root mean square differences (RMSSD) in the heart period. vmHRV biofeedback had neither an immediate effect on measures of cognitive control over long-term memory nor on phasic RMSSD. Moreover, neither resting-state nor phasic vmHRV correlated to the cognitive scores. Consequently, the utility of HRV biofeedback as a psychophysiological stimulation tool and a link between vmHRV and cognitive control over long-term memory could not be verified. Exploratory analyses revealed that baseline shift in parasympathetic activity confounded the psychophysiological association. Future directions are provided that could shed light on the relationship between cognition and vmHRV.

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.

Alcohol effects on interoception shape expectancies and subjective effects: a registered report using the heart rate discrimination task

AIMS

Alcohol acutely impacts interoceptive processes, which in turn affect the perception of alcohol effects and the development of alcohol expectancies. However, previous research is limited by the tools used to measure cardiac interoception and subjective alcohol effects. This registered report proposes a re-examination of previous findings using a state-of-the-art measure of interoceptive capacity, the heart rate discrimination task, and measurements of subjective alcohol effects across both ascending and descending limbs.

METHODS

In a double-blind, placebo-controlled experiment, n = 36 participants were given 0.4 g/kg of ethanol, and a baseline measure of alcohol expectancies was obtained. Changes in interoceptive capacity after beverage administration, along with measures of light-headedness, mood, and biphasic alcohol effects, were assessed over two sessions.

HYPOTHESES

As registered in this secondary data analysis, alcohol was expected to acutely impact different indices of interoceptive capacity, and those changes were hypothesized to correlate with subjective alcohol effects and expectancies. Analyses were conducted only following in-principle acceptance.

RESULTS

Alcohol-induced changes in interoceptive capacity predicted the development of light-headedness, stimulation, and negative mood. Changes in interoceptive capacity were also correlated with negative alcohol expectancies, as measured 2 weeks prior to the experiment. These effects were unique to the interoceptive condition, as null effects were observed in an exteroceptive control task.

DISCUSSION

This report offers a replication of key previous findings that alcohol impacts interoceptive processes to shape the detection of subjective alcohol effects. We propose that, through repeated drinking occasions, bodily responses feed into the experience of intoxication, shaping future expectancies about alcohol effects.

Attention to cardiac sensations enhances the heartbeat-evoked potential during exhalation

Respiration and cardiac activity intricately interact through complex physiological mechanisms. The heartbeat-evoked potential (HEP) is an EEG fluctuation reflecting the cortical processing of cardiac signals. We recently found higher HEP amplitude during exhalation than inhalation during a task involving attention to cardiac sensations. This may have been due to reduced cardiac perception during inhalation and heightened perception during exhalation through attentional mechanisms. To investigate relationships between HEP, attention, and respiration, we introduced an experimental setup that included tasks related to cardiac and respiratory interoceptive and exteroceptive attention. Results revealed HEP amplitude increases during the interoceptive tasks over fronto-central electrodes. When respiratory phases were taken into account, HEP increases were primarily driven by heartbeats recorded during exhalation, specifically during the cardiac interoceptive task, while inhalation had minimal impact. These findings emphasize the role of respiration in cardiac interoceptive attention and could have implications for respiratory interventions to fine-tune cardiac interoception.

High-intensity interval training (HIIT) and slow breathing interventions alleviate premature ejaculation (PE) symptoms

Background

Physical exercise may alleviate premature ejaculation symptoms, a prevalent male sexual dysfunction linked to a series of negative outcomes for men and their partners.

Objective

We investigated the effectiveness of high-intensity interval training (HIIT) and slow breathing interventions on premature ejaculation symptoms and their relation to autonomic activity and attention regulation.

Method

Chinese adult men (N = 76, M = 21.89, SD = 3.32) with premature ejaculation completed one of the two-week interventions in their homes or as participants in a normal breathing control group; they reported their age, height, weight, physical activity level, premature ejaculation symptoms, and attention regulation. In the HIIT group, 26 participants engaged in a 7-minute HIIT each day. In the slow breathing group, 25 participants performed 7-minute slow breathing exercises per day while the 25 participants in the normal breathing group similarly performed normal breathing exercises. All participants measured their heart rate once before and five times (with one-minute intervals) after the intervention. When participants had penile-vaginal sex with their partners, they measured their heart rate once after ejaculation.

Results

Time × Intervention interaction was significant with lower levels of premature ejaculation symptoms on Days 12, 13, and 14 in the HIIT group (M ± SD = 16.19 ± 3.45, 15.96 ± 3.43, and 15.15 ± 3.62) compared to the normal breathing group (M ± SD = 17.68 ± 3.06, 17.68 ± 3.15, and 17.44 ± 3.25). Higher levels of attention regulation were associated with fewer premature ejaculation symptoms. We also found that a larger increase in heart rate from resting to after sex was associated with fewer premature ejaculation symptoms.

Conclusion

Compared to the control group, the efficacy of two weeks of HIIT exercise in mitigating PE symptoms suggests its potential as a novel treatment for PE.

Virtual Reality Breathing Interventions for Mental Health: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Breathing exercises have been shown to reduce mental health problems among clinical and non-clinical populations. Although virtual reality (VR) breathing interventions are assumed to have potential benefits, it remains unclear whether VR breathing interventions are more effective at improving mental health than non-VR breathing interventions. We conducted a systematic literature search in six electronic databases (Web of Science, PsycINFO, Embase, Cochrane Central Register of Controlled Trials, Scopus, and PubMed) from inception to 30th September, 2022. We included randomized controlled trials in adults evaluating effects of VR compared to non-VR breathing interventions on primary outcomes of mental health (stress, anxiety and mood), and secondary outcomes of physiological stress measures (e.g., heart rate (HR), heart rate variability (HRV)). Within these selected studies, we explored differences in likeability and future use between VR and non-VR breathing interventions. 2.848 records were identified of which 65 full-text articles were assessed. Six RCTs were included, of which five were suitable for meta-analyses. Comparing VR to non-VR breathing interventions, there were no significant differences in overall mental health, stress, anxiety or mood, nor in HR or HRV. There was no evidence that participants liked VR breathing interventions more than non-VR, nor would use them more in the future. These results suggest that there is no evidence that VR breathing interventions are more effective than non-VR in improving mental health outcomes, HR, HRV. Further research is required to determine whether there may be advantages to longer-term VR-implementation and practice, and explore possible mechanisms.

An Estimation Formula for Resonance Frequency Using Sex and Height for Healthy Individuals and Patients with Incurable Cancers

Resonance frequency breathing is a technique that involves breathing that maximizes heart rate variability. It is specific to individuals and is determined through a procedure taking approximately 30 min, using a procedure that is often best carried out at specialized medical institutions. This is a physical and time-consuming burden because of hospital visits and measurements, particularly for patients with cancer. Therefore it would be beneficial if a procedure can be found to determine resonance frequency from the patient's physical characteristics, without the need for special assessment procedures. This exploratory cross-sectional study examined the correlation between individual characteristics and resonance frequency in healthy volunteers. Multiple regression analysis was performed with the measured resonance frequency as the target variable and individual characteristic parameters as explanatory variables. The study aims to build an estimation formula for resonance frequency with some of these parameters and assess its validity. In addition, the validity of the formula's applicability to patients with incurable cancers is assessed. A total of 122 healthy volunteers and 32 patients with incurable cancers were recruited as participants. The median resonance frequency of 154 participants was six breaths per min. Sex and height were selected as explanatory variables associated with the measured resonance frequency in the volunteers. The estimation formula for resonance frequency using individual characteristics was 17.90-0.07 × height for men and 15.88-0.06 × height for women. Adjusted R-squared values were 0.55 for men and 0.47 for women. When the measured resonance frequency in patients with incurable cancers was six breaths per minute or less, the resonance frequency estimated by this formula was slightly larger than the measured ones. Information on individual characteristics, such as sex and height, which can be easily obtained, was useful to construct an estimation formula for resonance frequency.

The Psychometric Properties of the Chinese version of the Interoceptive Awareness Questionnaire (IAQ) among PATIENTS WITH Cardiovascular Disease

BACKGROUND

Interoceptive awareness (perception of body conditions and processes) and heart rate variability are connected physiologically in cardiovascular disease (CVD) patients. At present, there is no specific evaluation model for the perception of the physical state and processes of CVD patients in China.

OBJECTIVES

The objective of this study is to examine the reliability and validity of the Chinese Interoceptive Awareness Questionnaire (C-IAQ) for Chinese CVD patients.

METHODS

160 CVD patients were recruited from a hospital in Hubei province using a convenient sampling method. A standard "forward-backward" translation method was applied to convert the C-IAQ into Mandarin. Split-half reliability and internal consistency were conducted by using reliability tests. Validity testing was conducted on the content, structure, and criterion-related validity. Criterion-related validity was assessed by using the Anxiety Sensitivity Index-III (ASI-III).

RESULTS

The research results indicate that the dual factor structure of the original C-IAQ has 19 items, including attention to unpleasant sensations (9 items) and awareness of neutral body sensations (10 items). Moreover, C-IAQ is positively correlated with ASI-III (r = 0.48, P<0.01). The entire scale has a Cronbach's α value of 0.85 and split-half dependability of 0.77.

CONCLUSION

The C-IAQ has favorable psychometric feature. Hence, it can be used to measure the interoceptive awareness of CVD patients.

The misjudgment of interoceptive awareness: Systematic overrating of interoceptive awareness among individuals with lower interoceptive metacognitive skills

Knowing when perceiving inner bodily signals better and when perceiving them worse is a health relevant but understudied dimension of interoception. Therefore, the present study assessed interoceptive metacognition (IMC) as the skill to adequately monitor interoceptive accuracy in the cardiac domain. We used the Graz Ambulatory Interoception task (GRAIT), which applied two intervals of the heartbeat tracking task 12 times a day for 3 days in total to n = 66 participants. We assessed IMC as the relative correspondence between interoceptive accuracy and the subjective confidence ratings. We found that 6 % of the total IMC variance was due to person, which was assessed reliable (RKRn=0.81). Furthermore, the between-person variation of IMC was negatively associated with the MAIA (especially attention regulation and self-regulation). People who believe that they are aware of their interoceptive experiences (MAIA) showed lower IMC. This study advocates the assessment of interoception in everyday life.

Complexity and Entropy in Physiological Signals (CEPS): Resonance Breathing Rate Assessed Using Measures of Fractal Dimension, Heart Rate Asymmetry and Permutation Entropy

BACKGROUND

As technology becomes more sophisticated, more accessible methods of interpretating Big Data become essential. We have continued to develop Complexity and Entropy in Physiological Signals (CEPS) as an open access MATLAB® GUI (graphical user interface) providing multiple methods for the modification and analysis of physiological data.

METHODS

To demonstrate the functionality of the software, data were collected from 44 healthy adults for a study investigating the effects on vagal tone of breathing paced at five different rates, as well as self-paced and un-paced. Five-minute 15-s recordings were used. Results were also compared with those from shorter segments of the data. Electrocardiogram (ECG), electrodermal activity (EDA) and Respiration (RSP) data were recorded. Particular attention was paid to COVID risk mitigation, and to parameter tuning for the CEPS measures. For comparison, data were processed using Kubios HRV, RR-APET and DynamicalSystems.jl software. We also compared findings for ECG RR interval (RRi) data resampled at 4 Hz (4R) or 10 Hz (10R), and non-resampled (noR). In total, we used around 190-220 measures from CEPS at various scales, depending on the analysis undertaken, with our investigation focused on three families of measures: 22 fractal dimension (FD) measures, 40 heart rate asymmetries or measures derived from Poincaré plots (HRA), and 8 measures based on permutation entropy (PE).

RESULTS

FDs for the RRi data differentiated strongly between breathing rates, whether data were resampled or not, increasing between 5 and 7 breaths per minute (BrPM). Largest effect sizes for RRi (4R and noR) differentiation between breathing rates were found for the PE-based measures. Measures that both differentiated well between breathing rates and were consistent across different RRi data lengths (1-5 min) included five PE-based (noR) and three FDs (4R). Of the top 12 measures with short-data values consistently within ± 5% of their values for the 5-min data, five were FDs, one was PE-based, and none were HRAs. Effect sizes were usually greater for CEPS measures than for those implemented in DynamicalSystems.jl.

CONCLUSION

The updated CEPS software enables visualisation and analysis of multichannel physiological data using a variety of established and recently introduced complexity entropy measures. Although equal resampling is theoretically important for FD estimation, it appears that FD measures may also be usefully applied to non-resampled data.

Interoception and alcohol: Mechanisms, networks, and implications

Interoception refers to the perception of the internal state of the body and is increasingly being recognized as an important factor in mental health disorders. Drugs of abuse produce powerful interoceptive states that are upstream of behaviors that drive and influence drug intake, and addiction pathology is impacted by interoceptive processes. The goal of the present review is to discuss interoceptive processes related to alcohol. We will cover physiological responses to alcohol, how interoceptive states can impact drinking, and the recruitment of brain networks as informed by clinical research. We also review the molecular and brain circuitry mechanisms of alcohol interoceptive effects as informed by preclinical studies. Finally, we will discuss emerging treatments with consideration of interoception processes. As our understanding of the role of interoception in drug and alcohol use grows, we suggest that the convergence of information provided by clinical and preclinical studies will be increasingly important. Given the complexity of interoceptive processing and the multitude of brain regions involved, an overarching network-based framework can provide context for how focused manipulations modulate interoceptive processing as a whole. In turn, preclinical studies can systematically determine the roles of individual nodes and their molecular underpinnings in a given network, potentially suggesting new therapeutic targets and directions. As interoceptive processing drives and influences motivation, emotion, and subsequent behavior, consideration of interoception is important for our understanding of processes that drive ongoing drinking and relapse.