Cardiac vagal activity during psychological stress varies with social functioning in older women

Self-Reported Emotion Regulation Is Associated With Response to Test of Cardiac Vagal Function

Abstract. Parasympathetic function and emotional self-regulation (ESR) share neuroanatomic structures. Based on Porges’ Polyvagal Theory and the Neurovisceral Integration Model (NIM), we compared vagally mediated heart-rate variability (vmHRV) with psychometrically assessed ESR. We hypothesized that vmHRV and ESR would be associated during rest, a vagal function test, and recovery from that test. A significant association would justify the psychometric measuring of parasympathetic health, which is less burdensome than its psychophysiological assessment. Two hundred thirteen healthy males (aged: 18–26 years, M = 20.29 years) took part in the present study. They completed the Emotion Regulation Questionnaire (ERQ) and underwent the Cold Face Test (CFT) for 4 min wearing ambulatory electrocardiograms. A High frequency (HF) band was used as a measure of vmHRV before, during, and after the CFT. Associations between the HF band and ESR were analyzed with partial rank correlations. There was no significant association between ERQ scores and the response to the CFT itself. But there was an almost significant association between the ERQ scale Cognitive Appraisal and baseline vmHRV, and a significant association between Cognitive Appraisal and cardiac recovery from the CFT, that is, participants with higher scores on that ESR scale revealed a tendency to exhibit greater vmHRV during baseline and they exhibited greater vagal withdrawal during recovery from the CFT. Cognitive appraisal as a psychometrically assessed emotion regulatory process was reflected in a more flexible parasympathetic activity (i.e., better cardiac vagal health) during recovery from an exclusively physiological stressor. This lends convergent validity to self-reported emotion regulation, and justification for its use as a measure of ESR as a trait, offering further support for the Polyvagal Theory and NIM.

Reactivity and recovery in romantic relationships following a trauma analog: Examination of respiratory sinus arrhythmia in community couples

Emotion regulation has important implications for individual and relationship health. Psychophysiological responses, such as respiratory sinus arrhythmia (RSA), can serve as a key indicator of emotion regulation processes subsequent to a stressor and may be the process by which couples confer health benefits. Moreover, partners in romantic relationships can mutually impact physiological states both during times of stress and times of support. The current study examined physiological reactivity through RSA during a laboratory stress-induction (i.e., stressful-film trauma analog) and recovery within the context of a romantic relationship. Sex, relationship health, and individual mental health indicators were examined as moderators of reactivity and recovery. Forty-five (n = 90 individuals) community couples, primarily White (n = 75, 83.3%), heterosexual (n = 63, 70.0%), and dating (n = 67, 74.4%), were examined. Both partners' RSA were measured continuously through a series of baseline tasks, a stressful-film task, and a post-film interaction task. Reactivity and recovery trajectories were moderated by sex, study task (i.e., baseline, film, and post-film), and individual mental health (ps < .05). Repeated-measures actor partner interdependence modeling analyses revealed a strong self-regulatory (i.e., actor) effect across all tasks as well as co-regulation (i.e., partner effects) during the post-film interaction task. Findings provided some evidence of stress transmission to the non-exposed partner. This study offers initial evidence of self- and co-regulation following a laboratory stress-induction and potential predictors and moderations of the set point and stability of these regulatory dynamics. Implications and future directions are discussed.

Autonomic influences on heart rate during marital conflict: Associations with high frequency heart rate variability and cardiac pre-ejection period

Psychosocial factors predict the development and course of cardiovascular disease, perhaps through sympathetic and parasympathetic mechanisms. At rest, heart rate (HR) is under parasympathetic control, often measured as high-frequency heart rate variability (HF-HRV). During stress, HR is influenced jointly by parasympathetic and sympathetic processes, the latter often quantified as pre-ejection period (PEP). In studies of cardiovascular risk factors that involve social interaction (e.g. marital conflict), HF-HRV might be altered by speech artifacts, weakening its validity as a measure of parasympathetic activity. To evaluate this possibility, we tested associations of HF-HRV and PEP with HR at rest and across periods of marital conflict interaction that varied in experimentally-manipulated degrees of speech in 104 couples. At rest, only HF-HRV was independently related to HR, for both husbands and wives. During speaking, listening, and recovery periods, husbands' and wives' HF-HRV and PEP change independently predicted HR change. These findings support interpretation of HF-HRV as a parasympathetic index during stressful social interactions that may confer risk for cardiovascular disease.

Validity of Commonly Used Heart Rate Variability Markers of Autonomic Nervous System Function

BACKGROUND

Despite strong reservations regarding the validity of a number of heart rate variability (HRV) measures, these are still being used in recent studies.

AIMS

We aimed to compare the reactivity of ostensible sympathetic HRV markers (low and very low frequency [LF and VLF]) to that of electrodermal activity (EDA), an exclusively sympathetic marker, in response to cognitive and orthostatic stress, investigate the possibility of LF as a vagal-mediated marker of baroreflex modulation, and compare the ability of HRV markers of parasympathetic function (root mean square of successive differences [RMSSD] and high frequency [HF]) to quantify vagal reactivity to cognitive and orthostatic stress.

RESULTS

None of the purported sympathetic HRV markers displayed a reactivity that correlated with electrodermal reactivity. LF (ms2) reactivity correlated with the reactivity of both RMSSD and HF during baroreflex modulation. RMSSD and HF indexed the reactivity of the parasympathetic nervous system under conditions of normal breathing; however, RMSSD performed better as a marker of vagal activity when the task required breathing changes.

CONCLUSIONS

Neither LF (in ms2 or normalized units [nu]) nor VLF represent cardiac sympathetic modulation of the heart. LF (ms2) may reflect vagally mediated baroreflex cardiac effects. HRV linear analysis therefore appears to be restricted to the determination of vagal influences on heart rate. With regard to HRV parasympathetic markers, this study supports the suggestion that HRV frequency domain analyses, such as HF, should not be used as an index of vagal activity in study tasks where verbal responses are required, as these responses may induce respiratory changes great enough to distort HF power.

Presidential Address 2011: Autonomic modes of control and health

Understanding psychosomatic relations, and their implications for heath, is importantly dependent on our conceptual and measurement models. The historical view of reciprocal control of the autonomic branches is applicable in some contexts, but not others. Control of the autonomic branches can vary reciprocally, independently, and even coactively. Assessment of sympathovagal balance, based on a reciprocal model of regulation of the autonomic branches, may have applications in orthostatic contexts and in insulin resistance in diabetes. However, it does not adequately capture the pattern of autonomic control that is relevant for myocardial infarction (MI; in humans) and experimental cardiac arrest (in mice). A measure of sympathovagal balance (cardiac autonomic balance) was predictive and informative of the autonomic contributions to diabetes but was blind to autonomic contributions to cardiac arrest and its sequelae. However, a metric designed to capture the coactivity dimension of cardiac autonomic regulation (CAR) was predictive of MI and its sequelae. Both human and animal model studies revealed that low CAR (low sympathetic and especially low parasympathetic control) predicted the occurrence of MI and the neuroinflammatory consequences of cardiac arrest. These effects were importantly modulated by social support in both humans and animals, via an apparent oxytocinergic pathway that impacts parasympathetic cardiac control and CAR, and thus neuroinflammation. Results indicate the importance of a physiologically meaningful model of autonomic control in understanding health implications of the modes of autonomic control.

Cardiac vagal control as a marker of emotion regulation in healthy adults: A review

In the last two decades, a growing body of theory and research has targeted the role of cardiac vagal control (CVC) in emotional responding. This research has either focused on resting CVC (also denoted as cardiac vagal tone) or phasic changes in CVC (also denoted as vagal reactivity) in response to affective stimuli. The present paper is aimed at reporting a review of the papers published between 1996 and 2016, and focused on the results of 135 papers examining cardiac vagal control as a physiological marker of emotion regulation in healthy adults. The review shows that studies have employed a wide array of methodologies and measures, often leading to conflicting results. High resting CVC has been associated with better down-regulation of negative affect, use of adaptive regulatory strategies, and more flexible emotional responding. Concerning phasic changes, research has consistently found decreased CVC in response to stress, while CVC increases have been shown to reflect either self-regulatory efforts or recovery from stress. Despite conflicting results, we conclude that existing literature supports the use of CVC as a noninvasive, objective marker of emotion regulation.

Heart Rate Variability and Cardiac Vagal Tone in Psychophysiological Research - Recommendations for Experiment Planning, Data Analysis, and Data Reporting

Psychophysiological research integrating heart rate variability (HRV) has increased during the last two decades, particularly given the fact that HRV is able to index cardiac vagal tone. Cardiac vagal tone, which represents the contribution of the parasympathetic nervous system to cardiac regulation, is acknowledged to be linked with many phenomena relevant for psychophysiological research, including self-regulation at the cognitive, emotional, social, and health levels. The ease of HRV collection and measurement coupled with the fact it is relatively affordable, non-invasive and pain free makes it widely accessible to many researchers. This ease of access should not obscure the difficulty of interpretation of HRV findings that can be easily misconstrued, however, this can be controlled to some extent through correct methodological processes. Standards of measurement were developed two decades ago by a Task Force within HRV research, and recent reviews updated several aspects of the Task Force paper. However, many methodological aspects related to HRV in psychophysiological research have to be considered if one aims to be able to draw sound conclusions, which makes it difficult to interpret findings and to compare results across laboratories. Those methodological issues have mainly been discussed in separate outlets, making difficult to get a grasp on them, and thus this paper aims to address this issue. It will help to provide psychophysiological researchers with recommendations and practical advice concerning experimental designs, data analysis, and data reporting. This will ensure that researchers starting a project with HRV and cardiac vagal tone are well informed regarding methodological considerations in order for their findings to contribute to knowledge advancement in their field.

Resting respiratory sinus arrhythmia is related to longer hospitalization in mood-disordered repetitive suicide attempters

OBJECTIVES

Our aims were (1) to measure respiratory sinus arrhythmia (RSA), a high-frequency spectrum component of heart rate variability (HRV) in mood-disordered suicide attempters and (2) to investigate the relationship of RSA to symptoms and length of hospitalization.

METHODS

Forty-nine female repetitive-suicide attempters with depressive disorder or bipolar disorder were recruited in a general hospital setting. Manic or psychotic patients were excluded. Resting RSA values were calculated from electrocardiogram data, and severity of clinical presentation shortly after admission and length of hospital stay were assessed.

RESULTS

RSA was positively associated with a higher Beck Scale for Suicidal Ideation score (r = 0.33 P = 0.019). Stepwise multiple regression analysis showed a significant correlation between RSA and hospitalization length after adjusting other variables (beta coefficient = 3.00; P = 0.030). Patients with a higher resting RSA had more prolonged hospitalizations (hospitalization beyond 30 days) after controlling for other variables (odds ratio = 5.08, P = 0.017).

CONCLUSIONS

Interaction between the environment and the autonomic nervous system is complex. Further and more comprehensive research is needed.

Social integration prospectively predicts changes in heart rate variability among individuals undergoing migration stress

BACKGROUND

Poor social integration increases risk for poor health. The psychobiological pathways underlying this effect are not well-understood.

PURPOSE

This study utilized a migration stress model to prospectively investigate the impact of social integration on change in high-frequency heart rate variability (HF-HRV), a marker of autonomic functioning.

METHODS

Sixty new international students were recruited shortly after their arrival in the host country and assessed 2 and 5 months later. At each assessment period, participants provided information on social integration and loneliness and had their resting HF-HRV evaluated.

RESULTS

There was an overall decrease in HF-HRV over time. The magnitude of the within-person and between-person effects of social integration on HRV increased over time, such that greater social integration was associated with higher HF-HRV at later follow-ups.

CONCLUSIONS

These results suggest that altered autonomic functioning might represent a key pathway linking social integration to health outcomes.

Interoceptive dysfunction: toward an integrated framework for understanding somatic and affective disturbance in depression

Depression is characterized by disturbed sleep and eating, a variety of other nonspecific somatic symptoms, and significant somatic comorbidities. Why there is such close association between cognitive and somatic dysfunction in depression is nonetheless poorly understood. An explosion of research in the area of interoception-the perception and interpretation of bodily signals-over the last decade nonetheless holds promise for illuminating what have until now been obscure links between the social, cognitive-affective, and somatic features of depression. This article reviews rapidly accumulating evidence that both somatic signaling and interoception are frequently altered in depression. This includes comparative studies showing vagus-mediated effects on depression-like behaviors in rodent models as well as studies in humans indicating both dysfunction in the neural substrates for interoception (e.g., vagus, insula, anterior cingulate cortex) and reduced sensitivity to bodily stimuli in depression. An integrative framework for organizing and interpreting this evidence is put forward which incorporates (a) multiple potential pathways to interoceptive dysfunction; (b) interaction with individual, gender, and cultural differences in interoception; and (c) a developmental psychobiological systems perspective, emphasizing likely differential susceptibility to somatic and interoceptive dysfunction across the lifespan. Combined with current theory and evidence, it is suggested that core symptoms of depression (e.g., anhedonia, social deficits) may be products of disturbed interoceptive-exteroceptive integration. More research is nonetheless needed to fully elucidate the relationship between mind, body, and social context in depression.

Adolescent RSA responses during an anger discussion task: Relations to emotion regulation and adjustment

The current study examined associations between adolescent respiratory sinus arrhythmia (RSA) during an angry event discussion task and adolescents' emotion regulation and adjustment. Data were collected from 206 adolescents (10-18 years of age, M age = 13.37). Electrocardiogram (ECG) and respiration data were collected from adolescents, and RSA values and respiration rates were computed. Adolescents reported on their own emotion regulation, prosocial behavior, and aggressive behavior. Multilevel latent growth modeling was employed to capture RSA responses across time (i.e., linear and quadratic changes; time course approach), and adolescent emotion regulation and adjustment variables were included in the model to test their links to RSA responses. Results indicated that high RSA baseline was associated with more adolescent prosocial behavior. A pattern of initial RSA decreases (RSA suppression) in response to angry event recall and subsequent RSA increases (RSA rebound) were related to better anger and sadness regulation and more prosocial behavior. However, RSA was not significantly linked to adolescent aggressive behavior. We also compared the time course approach with the conventional linear approach and found that the time course approach provided more meaningful and rich information. The implications of adaptive RSA change patterns are discussed.

Maladaptive autonomic regulation in PTSD accelerates physiological aging

A core manifestation of post-traumatic stress disorder (PTSD) is a disconnection between physiological state and psychological or behavioral processes necessary to adequately respond to environmental demands. Patients with PTSD experience abnormal oscillations in autonomic states supporting either fight and flight behaviors or withdrawal, immobilization, and dissociation without an intervening “calm” state that would provide opportunities for positive social interactions. This defensive autonomic disposition is adaptive in dangerous and life threatening situations, but in the context of every-day life may lead to significant psychosocial distress and deteriorating social relationships. The perpetuation of these maladaptive autonomic responses may contribute to the development of comorbid mental health issues such as depression, loneliness, and hostility that further modify the nature of cardiovascular behavior in the context of internal and external stressors. Over time, changes in autonomic, endocrine, and immune function contribute to deteriorating health, which is potently expressed in brain dysfunction and cardiovascular disease. In this theoretical review paper, we present an overview of the literature on the chronic health effects of PTSD. We discuss the brain networks underlying PTSD in the context of autonomic efferent and afferent contributions and how disruption of these networks leads to poor health outcomes. Finally, we discuss treatment approaches based on our theoretical model of PTSD.

Resting vagal control and resilience as predictors of cardiovascular allostasis in peacekeepers

The body's adaptive reaction to a stressful event, an allostatic response, involves vigorous physiological engagement with and efficient recovery from stress. Our aim was to investigate the influence of individual predispositions on cardiac responses to and recovery from a standardized psychosocial stress task (Trier Social Stress Task) in peacekeepers. We hypothesized that those individuals with higher trait resilience and those with higher resting vagal control would be more likely to present an allostatic response: a vigorous cardiac response to stress (i.e., reduction in interbeat intervals and heart rate variability (HRV)) coupled with a significant cardiac recovery in the aftermath. Fifty male military personnel with a mean age of 25.4 years (SD ± 5.99) were evaluated after returning from a peacekeeping mission. Electrocardiogram recordings were made throughout the experimental session, which consisted five conditions: basal, speech preparation, speech delivery, arithmetic task, and recovery. Mean interbeat intervals and HRV were calculated for each condition. An Ego-Resilience Scale and resting vagal control assessed individual predispositions. Stress tasks reduced interbeat intervals (tachycardia) and HRV in comparison with basal, with return to basal in the aftermath (p < 0.001, for all comparisons). Resilience and resting vagal control correlated positively with cardiac parameters for both stress reactivity and recovery (r ≥ 0.29; p < 0.05). In conclusion, peacekeepers showing higher trait resilience and those with higher resting vagal control presented a more adaptive allostatic reaction characterized by vigorous cardiac response to stress (i.e., tachycardia and vagal withdrawal) and efficient cardiac recovery after stress cessation.

Volitional control of the heart rate

The heart rate is largely under control of the autonomic nervous system. The aim of the present study is to investigate the interactions between the brain and heart underlying volitional control of the heart and to explore the effectiveness of volition as a strategy to control the heart rate without biofeedback. Twenty seven healthy male subjects voluntarily participated in the study and were instructed to decrease and increase their heart beats according to rhythmic, computer generated sound either 10% faster or slower than the subjects' measured heart rate. Sympathetic and parasympathetic activities were estimated with the heart rate variability (HRV) obtained by power spectral analysis of RR intervals. Functional coupling patterns of cerebral cortex with the heart were determined by Partial directed coherence (PDC). In HR(slow) task; HR and sympathetic activity significantly decreased. However parasympathetic activity and power spectral density of EEG in low Alpha (8-10.5 Hz) band significantly increased. Moreover information flow from parietal area (P3 and P4) to RR interval significantly increased. During HR(quick) task; HR, sympathetic activity and power spectral density of EEG in low Beta (14-24 Hz) band significantly increased. Parasympathetic activity significantly decreased. Information flow from FT8, CZ and T8 electrodes to RR interval significantly increased. Our findings suggested that the heart beat can be controlled by volition and is related to some special areas in the cortex.

Cardiac vagal tone is associated with social engagement and self-regulation

The polyvagal theory (Porges, 2007) represents a biobehavioral model that relates autonomic functioning to self-regulation and social engagement. The aim of the two presented studies was to test the proposed association of cardiac vagal tone (CVT), assessed via resting high-frequency heart rate variability (respiratory sinus arrhythmia, RSA), with coping, emotion-regulation, and social engagement in young adults. In Study 1 (retrospective self-report), RSA was positively associated with engagement coping (situation control, response control, positive self-instructions, social-support seeking) and aspects of social well-being. In Study 2 (ecological momentary assessment), for 28 days following the initial assessment, RSA predicted less use of disengagement strategies (acceptance and avoidance) for regulating negative emotions and more use of socially adaptive emotion-regulation strategies (i.e., social-support seeking as a reaction to sadness and making a concession as a reaction to anger caused by others). Furthermore, RSA was higher in participants who reported no anger episodes compared to those who reported at least one anger episode and was positively associated with reported episodes of negative emotions. Results support the association proposed by the PVT between CVT and self-regulatory behavior, which promotes social bonds.

Cardiac Vagal Tone and Quality of Parenting Show Concurrent and Time-Ordered Associations That Diverge in Abusive, Neglectful, and Non-Maltreating Mothers

Concurrent and lagged maternal respiratory sinus arrhythmia (RSA) was monitored in the context of parenting. One hundred and forty-one preschooler-mother dyads-involved with child welfare as documented perpetrators of child abuse or neglect, or non-maltreating (non-CM)-were observed completing a resting baseline and joint challenge task. Parenting behaviors were coded using SASB (Benjamin, 1996) and maternal RSA was simultaneously monitored, longitudinally-nested within-person (WP), and subjected to MLM. Abusive and neglectful mothers displayed less positive parenting and more strict/hostile control, relative to non-CM mothers. Non-CM mothers displayed greater WP heterogeneity in variance over time in their RSA scores, and greater consistency over time in their parenting behaviors, relative to abusive or neglectful mothers. CM group also moderated concurrent and lagged WP associations in RSA and positive parenting. When abusive mothers displayed lower RSA in a given epoch, relative to their task average, they showed concurrent increases in positive parenting, and higher subsequent levels of hostile control in the following epoch, suggesting that it is physiologically taxing for abusive mothers to parent in positive ways. In contrast, lagged effects for non-CM mothers were observed in which RSA decreases led to subsequent WP increases in positive parenting and decreases in control. Reversed models were significant only for neglectful mothers: Increases in positive parenting led to subsequent increases in RSA levels, and increases in strict, hostile control led to subsequent RSA decreases. These results provide new evidence that concurrent and time-ordered coupling in maternal physiology and behavior during parenting vary in theoretically meaningful ways across CM and non-CM mothers. Implications for intervention and study limitations are discussed.

Effects and possible mechanisms of acupuncture at ST36 on upper and lower abdominal symptoms induced by rectal distension in healthy volunteers

Background acupuncture (AP) has been shown to have a therapeutic potential for gastrointestinal motility disorders. The aims of this study were to investigate the effects and possible mechanisms of acupuncture on postprandial upper and lower abdominal symptoms induced by rectal distension (RD). Twenty healthy volunteers were involved in a two-session study (AP and sham-AP, AP and no-AP, or sham-AP and no-AP). In 12 of the volunteers, RD was performed for 60 min in the postprandial state, and AP at ST36 or sham-AP was performed during the second 30-min period of RD. Gastric slow waves and heart rate variability (HRV) were recorded using the electrogastrogram and electrocardiogram, respectively. Upper and lower abdominal symptoms were scored during RD with AP and sham-AP. In five of the subjects, an additional experiment with two sessions (with AP and no-AP) was performed. In the remaining eight volunteers, the same experiment was performed with sham-AP and no-AP was performed. The results were, first, RD at an average volume of 171 ml induced upper and lower abdominal symptoms (P < 0.01). AP, but not sham-AP or no-AP, reduced both upper and lower abdominal symptoms (P < 0.05). Second, RD decreased the percentage of normal gastric slow waves (P < 0.05). AP improved gastric slow waves compared with sham-AP or no-AP (P < 0.05). Third, in the larger, but not smaller, sample size experiment, the vagal activity during the RD plus AP period was significantly higher than that during the RD alone period in the same session and the corresponding period with sham-AP or no-AP in other sessions (P < 0.05). Neither sham-AP nor no-AP showed any effects on vagal activity (P > 0.05). Finally, in the experiment with eight volunteers, neither sham-AP nor no-AP showed any effects on RD-induced impairment in gastric slow waves, abdominal symptoms, or vagal activity (P > 0.05). The conclusions are RD induces upper or lower abdominal symptoms and impairs gastric slow waves in healthy volunteers. AP at ST36 is able to improve upper and lower abdominal symptoms and impaired gastric slow waves induced by RD, possibly mediated via the vagal pathway.

Effect of methamphetamine dependence on heart rate variability

Methamphetamine (METH) is an increasing popular and highly addictive stimulant associated with autonomic nervous system (ANS) dysfunction, cardiovascular pathology and neurotoxicity. Heart rate variability (HRV) has been used to assess autonomic function and predict mortality in cardiac disorders and drug intoxication, but has not been characterized in METH use. We recorded HRV in a sample of currently abstinent individuals with a history of METH dependence compared to age- and gender-matched drug-free comparison subjects. HRV was assessed using time domain, frequency domain, and non-linear entropic analyses in 17 previously METH-dependent and 21 drug-free comparison individuals during a 5 minute rest period. The METH-dependent group demonstrated significant reduction in HRV, reduced parasympathetic activity, and diminished heartbeat complexity relative to comparison participants. More recent METH use was associated with increased sympathetic tone. Chronic METH exposure may be associated with decreased HRV, impaired vagal function, and reduction in heart rate complexity as assessed by multiple methods of analysis. We discuss and review evidence that impaired HRV may be related to the cardiotoxic or neurotoxic effects of prolonged METH use.

Heart Rate Variability, Homeostasis, and Brain Function

Measures of heart rate variability (HRV) are major indices of the sympathovagal balance in cardiovascular research. These measures are thought to reflect complex patterns of brain activation as well and HRV is now emerging as a descriptor thought to provide information on the nervous system organization of homeostatic responses in accordance with the situational requirements. Current models of integration equate HRV to the affective states as parallel outputs of the central autonomic network, with HRV reflecting its organization of affective, physiological, “cognitive,” and behavioral elements into a homeostatic response. Clinical application is in the study of patients with psychiatric disorders, traumatic brain injury, impaired emotion-specific processing, personality, and communication disorders. HRV responses to highly emotional sensory inputs have been identified in subjects in vegetative state and in healthy or brain injured subjects processing complex sensory stimuli. In this respect, HRV measurements can provide additional information on the brain functional setup in the severely brain damaged and would provide researchers with a suitable approach in the absence of conscious behavior or whenever complex experimental conditions and data collection are impracticable, as it is the case, for example, in intensive care units.

Cardiac vagal control in nonmedicated depressed women and nondepressed controls: impact of depression status, lifetime trauma history, and respiratory factors

OBJECTIVE

To evaluate the impact of acute stress and relationship-focused imagery on cardiac vagal control, as indicated by levels of respiratory sinus arrhythmia (RSA), in depressed and nondepressed women. Impairment in cardiac parasympathetic (vagal) control may confer risk for cardiac mortality in depressed populations.

METHODS

Electrocardiogram and respiratory rate were evaluated in 15 nonmedicated depressed women and 15 matched controls during two laboratory conditions: 1) a relationship-focused imagery designed to elicit vagal activation; and 2) a speech stressor designed to evoke vagal withdrawal.

RESULTS

As expected, the relationship-focused imagery increased RSA (F(3,66) = 3.79, p = .02) and the speech stressor decreased RSA (F(3,66) = 4.36, p = .02) across women. Depressed women exhibited lower RSA during the relationship-focused imagery, and this effect remained after control for respiratory rate and trauma history (F(1,21) = 5.65, p = .027). Depressed women with a trauma history exhibited the lowest RSA during the stress condition (F(1,22) = 9.61, p = .05). However, after controlling for respiratory rate, Trauma History × Task Order (p = .02) but not Trauma History × Depression Group (p = .12) accounted for RSA variation during the stress condition.

CONCLUSION

Depression in women is associated with lower RSA, particularly when women reflect on a close love relationship, a context expected to elicit vagal activation and hence increase RSA. In contrast, depression-related variation in stressor-evoked vagal activity seems to covary with women's trauma history. Associations between vagal activity and depression are complex and should be considered in view of the experimental conditions under which vagal control is assessed, as well as physiological and behavioral factors that may affect vagal function.

Oxytocin increases autonomic cardiac control: moderation by loneliness

The current study examined the role of perceived social isolation in moderating the effects of oxytocin on cardiac autonomic control in humans. Intranasal administration of 20 IU oxytocin resulted in a significant increase in autonomic (parasympathetic and sympathetic) cardiac control. Specifically, oxytocin increased high frequency heart rate variability, a relatively pure measure of parasympathetic cardiac control, and decreased pre-ejection period, a well-validated marker of enhanced sympathetic cardiac control. Derived metrics of autonomic co-activity and reciprocity revealed that oxytocin significantly increased overall autonomic cardiac control. Furthermore, the effects of oxytocin on cardiac autonomic control were significantly associated with loneliness ratings. Higher levels of loneliness were associated with diminished parasympathetic cardiac reactivity to intranasal oxytocin. The effects of OT on autonomic cardiac control were independent of any effects on circulating pro-inflammatory cytokine or stress hormone levels. Thus, lonely individuals may be less responsive to the salubrious effects of oxytocin on cardiovascular responsivity.

Evaluation of the effect of topical application of lavender oil on autonomic nerve activity in dogs

OBJECTIVE

To investigate the effect of topical application of undiluted lavender oil on sympathovagal activity in dogs.

ANIMALS

5 healthy adult male Beagles.

PROCEDURES

An ambulatory ECG monitor (Holter recorder) was placed on each dog (day0), and 48-hour ECGs were recorded, beginning at 8:00 the next day (day 1). Lavender oil (0.18 mL) or saline (0.9% NaCl) solution (0.18 mL) was topically applied to the inner pinnas of both ears of all dogs at 8:30, 12:00, 15:30, and 19:00 on day 2. Each trial was duplicated in each dog, with an interval of 3 to 4 days between trials. Spectral indices of heart rate variability, power in the high-frequency range, and the ratio of low-frequency to high-frequency power were calculated as an indirect estimate of autonomic nerve activity.

RESULTS

When dogs were treated with lavender oil, the mean heart rate was significantly lower during the period of 19:00 to 22:30 on day 2, compared with the mean heart rate during the same period when dogs were treated with saline solution. On the other hand, high-frequency power during the period of 15:30 to 19:00 was significantly higher when dogs were treated with lavender oil, compared with the high-frequency power during the same period when dogs were treated with saline solution.

CONCLUSIONS AND CLINICAL RELEVANCE

The study revealed some evidence that topical application of lavender oil affected vagal activity in dogs. However, whether such an effect exists and whether lavender oil has a calming effect on dogs remains equivocal and requires additional investigation.