Cardiac Interbeat Interval Research Articles

MRMEBP: a unified framework for online detection of atrial fibrillation utilizing deep learning

Early detection of Atrial Fibrillation (AF) is essential for preventing heart failure, thrombosis, and cardio-embolic stroke. Traditional neural network (NN)-based detection methods primarily rely on clinical expert diagnoses, yet fully leveraging the intricate patterns inherent in AF episodes remains challenging. Herein, we propose an innovative framework that utilizes statistical inference and probabilistic modeling to analyze cardiac inter-beat interval dynamics, incorporating 5 robust features: heart rate, Differential entropy, minimal redundancy in non-AF episodes, and maximal entropy in AF episodes. The mRMEBP, a Back Propagation NN refined through rigorous optimization, accurately identifies subtle AF patterns. To enhance generalization, we utilize a diverse training set from 4 publicly accessible electrocardiogram (ECG) databases, featuring expert clinical annotations categorized into 6 types using a Fuzzy logic system. Validation against clinical data demonstrates the efficacy of mRMEBP, surpassing state-of-the-art techniques and highlighting its practical value in clinical and healthcare settings.

Behavioral variability in physiological synchrony during future-based conversations between romantic partners.

Physiological synchrony-or similarity between two people's physiological responses-is thought to have important consequences for health and well-being and has been observed in social relationship contexts. The present study investigated variability in dyads' physiological synchrony as a function of both partners' behaviors during an emotionally salient discussion. We examined concurrent covariation in cardiac interbeat intervals in a sample of young adult romantic couples (N = 79 dyads) who discussed the coordination of a personal goal with the future of their relationship (data collected from 2013 to 2015). Partners assigned to be disclosers revealed hypothetical good news (e.g., a dream job offer) with their partner, the responder, who reacted to this disclosure. To understand covariation-behavior associations, we examined three motivationally relevant behaviors that may underlie synchrony based on people's role in the discussion. We found significant variability in how much couples experienced covariation, and covariation depended, at least in part, on people's behaviors during the discussions. When disclosers spoke more (a behavior associated with less satisfying relationships and less positive partner perceptions), dyads experienced less physiological covariation. Furthermore, when responders showed more neglect and withdrawal, and when both partners displayed less positive emotion, dyads experienced less physiological covariation. These findings underscore couples' physiological synchrony as a heterogeneous process that can emerge with the presence of greater behavioral and emotional positivity. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Single neurons in the thalamus and subthalamic nucleus process cardiac and respiratory signals in humans

Visceral signals are constantly processed by our central nervous system, enable homeostatic regulation, and influence perception, emotion, and cognition. While visceral processes at the cortical level have been extensively studied using non-invasive imaging techniques, very few studies have investigated how this information is processed at the single neuron level, both in humans and animals. Subcortical regions, relaying signals from peripheral interoceptors to cortical structures, are particularly understudied and how visceral information is processed in thalamic and subthalamic structures remains largely unknown. Here, we took advantage of intraoperative microelectrode recordings in patients undergoing surgery for deep brain stimulation (DBS) to investigate the activity of single neurons related to cardiac and respiratory functions in three subcortical regions: ventral intermedius nucleus (Vim) and ventral caudalis nucleus (Vc) of the thalamus, and subthalamic nucleus (STN). We report that the activity of a large portion of the recorded neurons (about 70%) was modulated by either the heartbeat, the cardiac inter-beat interval, or the respiration. These cardiac and respiratory response patterns varied largely across neurons both in terms of timing and their kind of modulation. A substantial proportion of these visceral neurons (30%) was responsive to more than one of the tested signals, underlining specialization and integration of cardiac and respiratory signals in STN and thalamic neurons. By extensively describing single unit activity related to cardiorespiratory function in thalamic and subthalamic neurons, our results highlight the major role of these subcortical regions in the processing of visceral signals.

A new complex belief entropy of [formula omitted] divergence with its application in cardiac interbeat interval time series analysis

With outstanding capability to express uncertain information, complex evidence theory can be widely applied in a multiplicity of fields of representation and fusion of information. However, in complex evidence theory, conflict measurement is still an open issue. To address this problem, we propose a new complex belief χ2 divergence measure (CBχ2), which has the ability to measure the discrepancy between the complex basic belief assignments (CBBAs). In addition, the proposed CBχ2 divergence measure satisfies the properties of nonnegativity, nondegeneracy and symmetry. Particularly, when the CBBA degenerates to classical basic belief assignments (BBA), the proposed divergence can also measure the conflict well. On this basis, a novel BEoCBχ2D is proposed to measure the complexity of cardiac interbeat interval time series in biological system. An application in cardiac interbeat interval time series analysis demonstrates that BEoCBχ2D has better accuracy.

It does not need two: Assessing physiological linkage from videos across the valence dimension.

The phenomenon of physiological linkage describes similar fluctuations of two individuals' physiology, for example, the cardiac inter-beat interval (IBI). Physiological linkage is a well-documented occurrence in research settings of interacting dyads but the literature on non-interacting dyads, that is, someone watching a video of another person, is sparse. The current study investigated whether physiological linkage, based on IBI, occurs from watching videos where strangers report about personal (neutral, positive, negative non-traumatic, and negative traumatic) experiences. Videos were produced with six individuals and then presented to observers (N = 26). Time-frequency-domain cross-wavelet analyses supplemented by threshold-free cluster enhancement (TFCE; to account for multiple testing) showed significant physiological linkage between the IBI of observers and persons in the videos for 16 out of the 21 tested videos. Although significant physiological linkage also emerged for neutral videos and positive, negative valence videos led to such associations more reliably. This study shows that physiological linkage can be investigated in highly controlled conditions based on video stimuli paving the path for experimental manipulation in future research. Furthermore, due to the provision of information on time and frequency, the use of cross-wavelet analysis is encouraged to learn more about factors modulating physiological linkage. The current study presents the next step toward identifying psychophysiological causal and modulating factors of physiological linkage.

Diminished autonomic nervous system responses to acoustic startle in progressive supranuclear palsy (S8.003)

<h3>Objective:</h3> To examine possible autonomic changes associated with progressive supranuclear palsy in response to a strong, unanticipated stimulus. <h3>Background:</h3> Progressive supranuclear palsy (PSP) is a neurodegenerative disorder that causes serious problems in eye movements, walking, and balance, and is also often associated with cognitive, emotional, and behavioral changes. In other movement disorders such as Parkinson’s disease, similar symptoms have often been associated with changes in autonomic nervous system (ANS) functioning. Despite this, previous studies have rarely examined ANS functioning in PSP.. In the present study, we determined whether ANS responses to an emotionally provocative stimulus were altered in PSP. We tested the hypothesis that ANS responses to an unanticipated aversive auditory stimulus (i.e., a brief, loud burst of white noise) designed to induce a startle response would differ between patients with PSP compared to healthy controls (HC). <h3>Design/Methods:</h3> Participants included 33 PSP patients and 38 HC. Participants sat still for a 60 second baseline and heard a brief (100-ms) loud (115-dB) burst of white noise without warning. Continuous measures of cardiac interbeat intervals (IBI; decreases in IBI correspond to increases in heart rate) and skin conductance levels (SCL) were obtained throughout the task. <h3>Results:</h3> Compared to HC, PSP patients showed significantly less decrease in IBI (i.e., less increase in heart rate) and less increase in SCL from baseline during the 10 seconds after stimulus onset. <h3>Conclusions:</h3> Less decrease in IBI and less increase in SCL in the face of a strong external stimulus suggests a diminished sympathetic nervous system response. In light of previous research suggesting that peripheral sympathetic responses are relatively preserved in the setting of orthostatic postural testing in PSP, we suspect this relates to a brainstem degeneration in a pontine circuit that is critical for startle reflexes during emotional challenges. <b>Disclosure:</b> The institution of Dr. Pressman has received research support from Premiere. Dr. Pressman has received personal compensation in the range of $100,000-$499,999 for serving as a Associate Professor with University of Colorado School of Medicine. The institution of Dr. Chen has received research support from National Institute on Aging. Ms. Bullard has nothing to disclose. The institution of Dr. Rankin has received research support from Marcus Foundation. Robert Levenson has nothing to disclose.

Diminished preparatory physiological responses in frontotemporal lobar degeneration syndromes.

Researchers typically study physiological responses either after stimulus onset or when the emotional valence of an upcoming stimulus is revealed. Yet, participants may also respond when they are told that an emotional stimulus is about to be presented even without knowing its valence. Increased physiological responding during this time may reflect a ‘preparation for action’. The generation of such physiological responses may be supported by frontotemporal regions of the brain that are vulnerable to damage in frontotemporal lobar degeneration. We examined preparatory physiological responses and their structural and functional neural correlate in five frontotemporal lobar degeneration clinical subtypes (behavioural variant frontotemporal dementia, n = 67; semantic variant primary progressive aphasia, n = 35; non-fluent variant primary progressive aphasia, n = 30; corticobasal syndrome, n = 32; progressive supranuclear palsy, n = 30). Comparison groups included patients with Alzheimer’s disease (n = 56) and healthy controls (n = 35). Preparatory responses were quantified as cardiac interbeat interval decreases (i.e. heart rate increases) from baseline to an ‘instruction period’, during which participants were told to watch the upcoming emotional film but not provided the film’s valence. Patients’ behavioural symptoms (apathy and disinhibition) were also evaluated via a caregiver-reported measure. Compared to healthy controls and Alzheimer’s disease, the frontotemporal lobar degeneration group showed significantly smaller preparatory responses. When comparing each frontotemporal lobar degeneration clinical subtype with healthy controls and Alzheimer’s disease, significant group differences emerged for behavioural variant frontotemporal dementia and progressive supranuclear palsy. Behavioural analyses revealed that frontotemporal lobar degeneration patients showed greater disinhibition and apathy compared to Alzheimer’s disease patients. Further, these group differences in disinhibition (but not apathy) were mediated by patients’ smaller preparatory responses. Voxel-based morphometry and resting-state functional MRI analyses revealed that across patients and healthy controls, smaller preparatory responses were associated with smaller volume and lower functional connectivity in a circuit that included the ventromedial prefrontal cortex and cortical and subcortical regions of the salience network. Diminished preparatory physiological responding in frontotemporal lobar degeneration may reflect a lack of preparation for actions that are appropriate for an upcoming situation, such as approaching or withdrawing from emotional stimuli. The ventromedial prefrontal cortex and salience network are critical for evaluating stimuli, thinking about the future, triggering peripheral physiological responses, and processing and interpreting interoceptive signals. Damage to these circuits in frontotemporal lobar degeneration may impair preparatory responses and help explain often-observed clinical symptoms such as disinhibition in these patients.

Innovative approaches in investigating inter-beat intervals: Graph theoretical method suggests altered autonomic functioning in adolescents with ADHD.

Cardiac inter-beat intervals (IBIs) are considered to reflect autonomic functioning and self-regulatory abilities and are often investigated by traditional time- and frequency domain analyses. These analyses investigate IBI fluctuations across relatively long time series. The similarity graph algorithm is a nonlinear method that analyzes segments of IBI time series (i.e., time windows)-possibly being more sensitive to transient and spontaneous IBI fluctuations. We hypothesized that the similarity graph algorithm would detect differences between Attention-Deficit/Hyperactivity Disorder (ADHD) and control groups. Resting electrocardiogram (ECG) recordings were collected in 10-18-year-olds with ADHD (n=37) and controls (n=36). IBIs were converted to graphs that were subsequently investigated for similarity. We varied the criterion for defining IBIs as similar, assessing which setting best distinguished ADHD and control groups. Using this setting, we applied the similarity graph algorithm to time windows of 2-5, 6-13 and 12-25s, respectively. We also performed traditional IBI analyses. Independent samples t tests assessed group differences. Results showed that a 1.5% criterion of similarity and a time window of 2-5s best distinguished adolescents with ADHD and controls. The similarity graph algorithm showed a higher number of edges, maximum edges and cliques, and lower edges10+10/edges2+2 in the ADHD group compared to controls. The results suggested more similar IBIs in the ADHD group compared to the controls, possibly due to altered vagal activity and less effective regulation of heart rate. Traditional analyses did not detect any group differences. Consequently, the similarity graph algorithm might complement traditional IBI analyses as a marker of psychopathology.

Belief entropy-of-entropy and its application in the cardiac interbeat interval time series analysis

How to measure the complexity of physiological signals in biological system is an open problem. Various entropy algorithms have been presented, but most of them fail to account for the complexity of time series with high accuracy. In this paper, the concept of Belief Entropy-of-Entropy (BEoE) is introduced, it expands entropy of entropy (EoE) into belief structure, and computes quadratic belief entropy to characterize the complexity of biological systems based on multiple time scales. The influence of inherent complex fluctuation, length bound, correlation of time windows, etc. is considered in the BEoE analysis. Application and discussion demonstrate that BEoE has better accurateness and applicability than many existing entropy algorithms.

Oxytocin increases physiological linkage during group therapy for methamphetamine use disorder: a randomized clinical trial

Patients and psychotherapists often exhibit behavioral, psychological, and physiological similarity. Here, we test whether oxytocin—a neuropeptide that can enhance expressivity and social perception—influences time-lagged “linkage” of autonomic nervous system responses among participants and facilitators during group therapy. Physiological linkage estimates (n = 949) were created from ten cohorts, each with two facilitators (n = 5) and four to six participants (n = 48), over six weekly sessions of group therapy for methamphetamine use disorder. All participants of a cohort received oxytocin or placebo intranasally in a randomized double-blind procedure before each session. Cardiac interbeat intervals (IBI) were measured continuously during sessions to estimate physiological linkage, operationalized as one cohort-mate’s IBI reactivity during one minute predicting another cohort-mate’s IBI reactivity during the following minute. In oxytocin cohorts, participants and facilitators experienced significant physiological linkage to their cohort-mates (i.e., their physiological responses were predicted by the prior responses of their cohort-mates) and significantly more linkage than people in placebo cohorts. Both effects occurred during the first and second sessions but not later sessions. Results suggest that oxytocin may enhance psychosocial processes often associated with linkage—such as social engagement—in groups and highlight oxytocin’s potential to improve group cohesion during group therapy.Clinical Trials Registration: NCT02881177, First published on 26/08/2016.

The Immediate Effect of Parachute-Resisted Gallop on Heart Rate, Running Speed and Stride Frequency in Dogs.

Simple SummaryPhysical fitness is needed for canine athletes and working dogs to optimize their performance in various disciplines. Application of resistance on movements causes biomechanical and cardiorespiratory responses to physical exercise. However, there is still a lack of research on the effects of high-intensity resistance exercise on cardiorespiratory fitness components such as heart rate in canine athletes. In this article, we investigate the short-term effects of parachute-resisted galloping on heart rate, running speed and stride frequency. Healthy dogs of various breeds were extensively studied in five experimental single cases. The dogs ran on a straight 200 m course with and without resistive drag force applied by a parachute attached to their harness while heart rate, running speed and stride frequency were measured. Subsequently, the measurements were compared to baseline phases at rest. In the present trials we found that heart rate increases similarly with and without parachute-resistance while dogs galloped at lower speeds and with increased stride frequency with applied drag force. Our findings lead us to suggest that parachute-resisted galloping is a clinically applicable exercise in healthy dogs to achieve instant cardiorespiratory response.Physical fitness is required for canine athletes and working dogs to optimize performance in various disciplines. There is a lack of research on the effects of resistance exercise on cardiorespiratory variables in dogs. The aim of this study was to investigate the immediate effects of parachute-resisted (PR) gallop on heart rate, running speed and stride frequency compared to unresisted (UR) gallop in dogs. Five N-of-1 trials RCTs with alternating interventions were implemented. Dogs ran on a 200 m course with and without resistive force applied by a parachute attached to their harness while cardiac inter-beat intervals (IBI), running speed and stride frequency were measured. The results were visually displayed and interpreted in graphs and percentage of non-overlapping data estimated effect size. Both interventions showed large effects on heart rate compared to resting values. Mean IBI increased (10–17%) during PR gallop compared to UR gallop although this change was small relative to decreased running speed (19–40%) and increased stride frequency (18–63%). Minimum IBI showed no difference between interventions indicating similar maximum heartbeat per minute. In conclusion, parachute-resistance resulted in dogs galloping at lower speeds at the same cardiorespiratory level of intensity, which may be useful in canine physical rehabilitation and fitness training.

Defensive functions provoke similar psychophysiological reactions in reaching and comfort spaces

The space around the body crucially serves a variety of functions, first and foremost, preserving one’s own safety and avoiding injury. Recent research has shown that emotional information, in particular threatening facial expressions, affects the regulation of peripersonal-reaching space (PPS, for action with objects) and interpersonal-comfort space (IPS, for social interaction). Here we explored if emotional facial expressions may similarly or differently affect both spaces in terms of psychophysiological reactions (cardiac inter-beat intervals: IBIs, i.e. inverse of heart rate; Skin Conductance Response amplitude: SCR amplitude) and spatial distance. Through Immersive Virtual Reality technology, participants determined reaching-distance (PPS) and comfort-distance (IPS) from virtual confederates exhibiting happy/angry/neutral facial expressions while being approached by them. During these interactions, spatial distance and psychophysiological reactions were recorded. Results revealed that when interacting with angry virtual confederates the distance increased similarly in both comfort-social and reaching-action spaces. Moreover, interacting with virtual confederates exhibiting angry rather than happy or neutral expressions provoked similar psychophysiological activations (SCR amplitude, IBIs) in both spaces. Regression analyses showed that psychophysiological activations, particularly SCR amplitude in response to virtual confederates approaching with angry expressions, were able to predict the increase of PPS and IPS. These findings suggest that self-protection functions could be the expression of a common defensive mechanism shared by social and action spaces.

Complexity and Disorder of 1/fα Noises.

The complexity and the disorder of a 1/ noise time series are quantified by entropy of entropy (EoE) and average entropy (AE), respectively. The resulting EoE vs. AE plot of a series of 1/ noises of various values of exhibits a distinct inverted U curve. For the 1/ noises, we have shown that decreases monotonically as AE increases, which indicates that is also a measure of disorder. Furthermore, a 1/ noise and a cardiac interbeat (RR) interval series are considered equivalent as they have the same AE. Accordingly, we have found that the 1/ noises for around 1.5 are equivalent to the RR interval series of healthy subjects. The pink noise at = 1 is equivalent to atrial fibrillation (AF) RR interval series while the white noise at = 0 is more disordered than AF RR interval series. These results, based on AE, are different from the previous ones based on spectral analysis. The testing macro-average F-score is 0.93 when classifying the RR interval series of three groups using AE-based , while it is 0.73 when using spectral-analysis-based .

Validating Measures of Electrodermal Activity and Heart Rate Variability Derived From the Empatica E4 Utilized in Research Settings That Involve Interactive Dyadic States.

Portable and wireless devices that collect physiological data are becoming more and more sought after in clinical and psychophysiological research as technology swiftly advances. These devices allow for data collection in interactive states, such as dyadic therapy, with reduced restraints compared to traditional laboratory devices. One such portable device is the Empatica E4 wristband (Empatica Srl, Milan, Italy) which allows quantifying cardiac interbeat intervals (IBIs), heart rate variability (HRV), and electro-dermal activity (EDA), as well as several other acceleration and temperature measures. In the current study, we aimed to assess IBI, HRV, and EDA measures, against the same data collected from the well-validated MindWare mobile impedance cardiograph device (MindWare Technology, Gahanna, OH, United States). We assessed the E4 strictly as a research instrument and not as a clinical tool. We were specifically interested in the wristbands’ performance during naturalistic interactive face-to-face conversations which inherently involve more hand movements. We collected data from 30 participants, nested in 15 dyads, which were connected to both devices simultaneously, during rest and during a social conversation. After preprocessing and analyses, we found that mean IBIs obtained by the E4 and the MindWare device, were highly similar during rest and during conversation. Medium to high correlations were found between the devices with respect to several HRV measures, with higher correlations during rest compared to conversation. The E4 failed to produce reliable EDA data. We conclude by discussing the strengths and limitations of the E4 during seated conversational states and suggest optimal ways to collect and analyze data with the E4.

Physiological linkage among successful high-status women in international teams.

In contemporary society, decisions are often made by teams whose members represent different nationalities and genders. In the current work, participants from 55 countries formed groups of 3 to 4 people to select one of the 5 firms in a mock firm search. In all groups, one woman was randomly assigned to have higher status than her groupmates; she was also surreptitiously instructed to persuade her group to select one (randomly assigned) firm. We measured cardiac interbeat intervals for participants throughout the decision-making process to assess physiological linkage—the degree to which a ‘sender’s’ physiological response predicts a ‘receiver’s’ physiological response at a subsequent time interval. On average, high-status women were successful at persuasion. The physiological responses of successful high-status women were also predicted by the responses of their female groupmates: stronger linkage to female group members during the task was associated with success at persuading the group. Successful high-status women were also perceived as more persuasive than others in the group. This work shows that the link between status and successful persuasion generalizes to women among heterogeneous international teams. It also suggests that attention to others—often associated with physiological linkage—may be useful in persuading others during decision-making.

Coherence between subjective experience and physiology in emotion: Individual differences and implications for well-being.

Emotion theorists have characterized emotions as involving coherent responding across various emotion response systems (e.g., covariation of subjective experience and physiology). Greater response system coherence has been theorized to promote well-being, yet very little research has tested this assumption. The current study examined whether individuals with greater coherence between physiology and subjective experience of emotion report greater well-being. We also examined factors that may predict the magnitude of coherence, such as emotion intensity, cognitive reappraisal, and expressive suppression. Participants (N = 63) completed self-report measures of well-being, expressive suppression, and cognitive reappraisal. They then watched a series of emotionally evocative film clips designed to elicit positive and negative emotion. During the films, participants continuously rated their emotional experience using a rating dial, and their autonomic physiological responses were recorded. Time-lagged cross-correlations were used to calculate within-participant coherence between intensity of emotional experience (ranging from neutral to very negative or very positive) and physiology (composite of cardiac interbeat interval, skin conductance, ear pulse transit time, finger pulse transit time and amplitude, systolic and diastolic blood pressure). Results indicated that individuals with greater coherence reported greater well-being. Coherence was highest during the most emotionally intense film and among individuals who reported lower expressive suppression. However, coherence was not associated with reappraisal. These findings provide support for the idea that greater emotion coherence promotes well-being and also shed light on factors that are associated with the magnitude of coherence. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Effects of Therapeutic Intervention on Parentally Bereaved Children's Emotion Reactivity and Regulation 15Years Later.

The Family Bereavement Program (FBP) is a family-based intervention for parentally bereaved children and surviving caregivers. Results are reported of a randomized controlled trial, examining intervention effects on emotional reactivity and regulation of young adults who participated in the program 15years earlier. Participants (N = 152) completed four emotion challenge tasks: reactivity to negative images, detached reappraisal while viewing negative images, positive reappraisal while viewing negative images, and reengagement with positive images. Outcomes included cardiac interbeat interval (IBI), pre-ejection period (PEP), and respiratory sinus arrhythmia (RSA) as well as self-reported emotional experience and regulation effectiveness. Direct intervention effects and effects mediated through improved parenting were estimated. Several significant effects were observed in primary analyses; however, none remained significant after correction for familywise Type I error. Parentingmediated FBP effects on IBI during negative reactivity (b = 15.04), and on RSA during positive reengagement (b = 0.35); the latter effect was accounted for by changes in breathing. Intervention condition was a direct predictor of self-reported detached reappraisal effectiveness (b = 1.00). Intervention and gender interacted in predicting self-reported negative emotion during the negative reactivity (b = 1.04) and positive reappraisal tasks (b = 1.31) such that intervention-conditionmen reported more negative emotions during those tasks. Although these findings should be considered preliminary given the limited power of the corrected statistical tests, they suggest long-term effects of family intervention following the death of a parent on offspring's emotional reactivity and regulation ability that should be pursued further in future research.

Heart Rate and Breathing Are Not Always in Phase During Resonance Frequency Breathing.

For many years it has been an axiom among practitioners of heart rate variability biofeedback that heart rate and breathing vary in phase with each other when people do resonance frequency breathing. When people breathe at the frequency of the baroreflex system, about 0.1Hz, heart rate and blood pressure have been found to oscillate 180° out of phase, while heart rate and breathing are in phase (zero-degree phase). Thus breathing stimulates the baroreflex by augmenting the baroreflex response with each breath, an effect that is magnified by resonance properties in the baroreflex system. The original data on these relationships came from a study of highly athletic healthy young people. To test this relationship we analyzed phase relationship data between cardiac interbeat interval and breathing during 5-min periods of resonance frequency breathing among 24 adults from a recent study of heart rate variability biofeedback to treat adults with mild to moderate currently symptomatic asthma, ages between 18 and 70. For the specific frequency near 0.1Hz with the highest amplitude of HRV we calculated coherence and phase between cardiac interbeat interval (IBI) and the respiration curve using the WinCPRS program. Among records with coherence > 0.8, we found a phase relationship of 109° rather than the expected 180°, with IBI changes leading breathing. We computed Spearman correlation coefficients between phase and various subject characteristics, including age, gender, height, and asthma severity. We found no relationship between phase and gender, height, or asthma physiology or symptoms. However, when controlled for gender and height, we found a moderate size significant correlation between phase and age, with younger participants having values closer to 180°, r = 0.47, p < 0.03. It is possible that cardiovascular characteristics of older people affect the phase relationship. Despite the deviation from the in-phase relationship among older individuals, breathing nevertheless stimulated the baroreflex and produced high-amplitude heart rate oscillations. Implications are discussed for HRV biofeedback training protocols. Replication in a healthy population is needed in order to determine the universality of these findings.

Influencing the physiology and decisions of groups: Physiological linkage during group decision-making

Many of the most important decisions in our society are made within groups, yet we know little about how the physiological responses of group members predict the decisions that groups make. In the current work, we examine whether physiological linkage from “senders” to “receivers”—which occurs when a sender’s physiological response predicts a receiver’s physiological response—is associated with senders’ success at persuading the group to make a decision in their favor. We also examine whether experimentally manipulated status—an important predictor of social behavior—is associated with physiological linkage. In groups of 5, we randomly assigned 1 person to be high status, 1 low status, and 3 middle status. Groups completed a collaborative decision-making task that required them to come to a consensus on a decision to hire 1 of 5 firms. Unbeknownst to the 3 middle-status members, high- and low-status members surreptitiously were told to each argue for different firms. We measured cardiac interbeat intervals of all group members throughout the decision-making process to assess physiological linkage. We found that the more receivers were physiologically linked to senders, the more likely groups were to make a decision in favor of the senders. We did not find that people were physiologically linked to their group members as a function of their fellow group members’ status. This work identifies physiological linkage as a novel correlate of persuasion and highlights the need to understand the relationship between group members’ physiological responses during group decision-making.

Effects of sleep on a high-heat capacity mattress on sleep stages, EEG power spectra, cardiac interbeat intervals and body temperatures in healthy middle-aged men‡.

This study deals with the question whether a slow (non-disturbing) reduction of core body temperature (CBT) during sleep increases sleep stage N3 and EEG slow wave energy (SWE) and leads to a slowing of heart rate in humans. Thirty-two healthy male subjects with a mean ± SD age 46 ± 4 years and body mass index 25.2 ± 1.8 kg/m2. A high-heat capacity mattress (HM) was used to lower body temperatures in sleep and was compared to a conventional low-heat capacity mattress (LM) in a double-blinded fashion. Polysomnography was performed accompanied by measurements of skin-, core body- and mattress surface-temperatures, and heart rate. EEG power spectral analyses were carried out using Fast Fourier Transform. Interbeat intervals were derived from the electrocardiogram. The HM led to a larger decline in CBT, mediated through higher heat conduction from the core via the proximal back skin onto the mattress together with reduced heart rate. These effects occurred together with a significant increase in sleep stage N3 and standardized slow wave energy (sSWE, 0.791-4.297 Hz) accumulated in NREM sleep. In the 2nd half of the night sSWE increase was significantly correlated with body temperature changes, for example with CBT decline in the same phase. A HM subtly decreases CBT, leading to an increased amount of sleep stage N3 and of sSWE, as well as a slowing of heart rate.