Assessing the Relationship Between Emotional States of Dogs and Their Human Handlers, Using Simultaneous Behavioral and Cardiac Measures.

Negative stress due to human handling has been reported for a number of domestic animals, including dogs. Many companion dogs display significant stress during routine care in the veterinary clinic, risking injury to staff and potentially compromising the quality of care that these dogs receive. On the other hand, positive interactions with humans can have a beneficial effect on dogs, particularly in stressful situations such as animal shelters. Research has shown that dogs can detect human emotions through visual, auditory, and chemical channels, and that dogs will exhibit emotional contagion, particularly with familiar humans. This study investigated relationships between emotional states of dogs and unfamiliar human handlers, using simultaneous measures of cardiac activity and behavior, during two sessions of three consecutive routine handling sets. Measures of cardiac activity included mean heart rate (HRmean), and two measures of heart rate variability (HRV): the root mean square of successive differences between normal heartbeats (RMSSD); and the high frequency absolute power component of HRV, log transformed (HFlog). We also assessed human handlers' emotional state during handling sessions following an intervention designed to reduce stress, compared with sessions conducted on a different day and following a control activity. Polar H10 cardiac sensors were used to simultaneously record cardiac activity for both canine and human participants, and behavioral data were collected via digital video. The strongest influence on the dogs' stress levels in our study was found to be increasing familiarity with the setting and the handler; HRmean and SI decreased, and HRV (as RMSSD) increased, significantly from the first to the third handling set. Canine HRV (as HFlog) was also highest in set 3, although the difference was not statistically significant. There were no strong patterns found in the human cardiac data across handling set, session, or by pre-handling activity. We did not find consistent support for emotional contagion between the dogs and their handlers in this study, perhaps due to the brief time that the dogs spent with the handlers. Recommendations for application to dog handling, and limitations of our methods, are described.

Menstrual Type, Pain and Psychological Distress in Adult Women with Sickle Cell Disease (SCD).

OBJECTIVE: We evaluated the effects of menstrual types inclusive of PMS on reports of chronic pain intensity and psychopathology in twenty-eight women (mean age 38.93 ± 13.51) with Sickle Cell disease (SCD). METHODS: Using the Menstrual Symptoms Questionnaire, we compared women with PMS to those with less distressing spasmodic cycle types. RESULTS: Thirty-four percent of the sample used oral contraception; there were no significant effects of birth control use on reports of pain. Women with PMS characterized the sensory (p = .04) and affective (p = .04) experiences of their SCD-related chronic pain, including their current pain intensity (p = .03), as significantly greater than women with primary spasmodic menstrual type. Further, there was a trend towards significance for women with PMS to report greater levels of overall pain intensity (p = .07) and average pain intensity over the past month (p = .08). CONCLUSIONS: The authors interpret these results to suggest that there may be a complex interaction of neurohormonal, biological, and psychological factors associated with PMS that influence manifestation and experience of chronic pain in patients with SCD.

Stereotype threat, trait perseveration, and vagal activity: evidence for mechanisms underpinning health disparities in Black Americans.

Objective: Black Americans (BAs) are at an elevated risk for morbidity and mortality in comparison to White Americans (WAs). Racial stressors are a common occurrence in American culture and is theorized to contribute to these disparities. When race-focused, stereotype threat (ST) is considered to be a factor that is detrimental to health in BAs; however few studies have directly investigated the impact of a ST manipulation on physiological function. Furthermore, it is proposed that racial stressors such as ST may have prolonged effects when more likely to perseverate (e.g. rumination) over the stressor and thus, those with greater trait perseveration may be more affected by ST. We sought to explore the impact of ST and trait perseveration on changes in vagus nerve activity - an indication of adaptive psychological and physiological well-being - as indexed by vagally mediated heart rate variability (vmHRV). Design: Forty-three (24 females, mean age of 20, standard deviation of 3 years) apparently healthy BA individuals were randomly assigned to one of three experimental conditions in which they received either implicit (subtle), explicit (blatant), or no ST priming (control condition), prior to completing a cognitive task. Resting vmHRV was assessed both at baseline (pre-task) and recovery (post-task). Results: BAs in the explicit ST condition exhibited the greatest decrease in vmHRV in comparison to the control group from pre- to post-task. BAs with moderate to high levels of trait perseveration showed the greatest decrease in vmHRV from pre- to post-task in comparison to those with lower levels of trait perseveration and BAs in the control group. Conclusion: These data suggest that racial ST, especially when explicit and coupled with trait perseveration, can decrease vagal activity, as indexed by decreased vmHRV, which when experienced frequently can have significant consequences for health and longevity in BAs.

Systematic Review of Biofeedback Interventions for Addressing Anxiety and Depression in Children and Adolescents with Long-Term Physical Conditions.

Children and adolescents with long-term physical conditions are at increased risk of psychological problems, particularly anxiety and depression, and they have limited access to evidence-based treatment for these issues. Biofeedback interventions may be useful for treating symptoms of both psychological and physical conditions. A systematic review of studies of biofeedback interventions that addressed anxiety or depression in this population was undertaken via MEDLINE, EMBASE, PsycINFO, CINAHL and the Cochrane Central Register of Controlled Trials databases. Primary outcomes included changes in anxiety and depression symptoms and 'caseness'. Secondary outcomes included changes in symptoms of the associated physical condition and acceptability of the biofeedback intervention. Of 1876 identified citations, 9 studies (4 RCTs, 5 non-RCTs; of which all measured changes in anxiety and 3 of which measured changes in depression) were included in the final analysis and involved participants aged 8-25 years with a range of long-term physical conditions. Due to the heterogeneity of study design and reporting, risk of bias was judged as unclear for all studies and meta-analysis of findings was not undertaken. Within the identified sample, multiple modalities of biofeedback including heart rate variability (HRV), biofeedback assisted relaxation therapy and electroencephalography were found to be effective in reducing symptoms of anxiety. HRV was also found to be effective in reducing symptoms of depression in two studies. A range of modalities was effective in improving symptoms of long-term physical conditions. Two studies that assessed acceptability provided generally positive feedback. There is currently limited evidence to support the use of biofeedback interventions for addressing anxiety and depression in children and adolescents with long-term physical conditions. Although promising, further research using more stringent methodology and reporting is required before biofeedback interventions can be recommended for clinical use instead or in addition to existing evidence-based modalities of treatment.

A comparison of the cardiovascular effects of simulated and spontaneous laughter.

OBJECTIVES: Laughter has long been regarded as beneficial for health, but the mechanisms are not clearly understood. The current study aimed to compare the acute cardiovascular effects of spontaneous and simulated laughter. DESIGN: A mixed factorial experiment was performed to examine changes in cardiovascular variables in response to experimental tasks across conditions. INTERVENTIONS: A sample of 72 participants were randomised to one of three 6 min interventions. Participants in the simulated laughter condition were asked to generate fake laughter, the spontaneous laughter condition viewed a humorous video, and the control condition watched a non-humorous documentary. This was followed by a laboratory stress task. MAIN OUTCOMES MEASURES: Heart rate and heart rate variability (as indexed by rMSSD) were monitored continuously throughout the experiment using ECG. RESULTS: The simulated laughter condition had a significantly higher heart rate (p < .001, ηp2 = .26) and lower rMSSD (p < .001, ηp2 = .13) during the laughter task compared to the other two conditions. Follow-up hierarchical regressions indicated that the difference in heart rate was due to the fact that the simulated condition produced more laughter. The difference in rMSSD, however, was unique to the simulated condition even when controlling for the amount of laughter. The simulated laughter condition had a significantly lower mean HR during the stress task but this was not significant after controlling amount of laughter produced. CONCLUSIONS: Laughter leads to increased heart rate and reduced heart rate variability, which is similar to the effects of exercise. This finding is more pronounced in simulated laughter.

Visual cue-specific craving is diminished in stressed smokers.

BACKGROUND: Craving among smokers is increased by stress and exposure to smoking-related visual cues. However, few experimental studies have tested both elicitors concurrently and considered how exposures may interact to influence craving. OBJECTIVE: The current study examined craving in response to stress and visual cue exposure, separately and in succession, in order to better understand the relationship between craving elicitation and the elicitor. METHOD: Thirty-nine smokers (21 males) who forwent smoking for 30 minutes were randomized to complete a stress task and a visual cue task in counterbalanced orders (creating the experimental groups); for the cue task, counterbalanced blocks of neutral, motivational control, and smoking images were presented. Self-reported craving was assessed after each block of visual stimuli and stress task, and after a recovery period following each task. RESULTS: As expected, the stress and smoking images generated greater craving than neutral or motivational control images (p < .001). Interactions indicated craving in those who completed the stress task first differed from those who completed the visual cues task first (p < .05), such that stress task craving was greater than all image type craving (all p's < .05) only if the visual cue task was completed first. Conversely, craving was stable across image types when the stress task was completed first. CONCLUSIONS: Findings indicate when smokers are stressed, visual cues have little additive effect on craving, and different types of visual cues elicit comparable craving. These findings may imply that once stressed, smokers will crave cigarettes comparably notwithstanding whether they are exposed to smoking image cues.

Higher resting heart rate variability predicts skill in expressing some emotions.

Vagally mediated heart rate variability (vmHRV) is a measure of cardiac vagal tone, and is widely viewed as a physiological index of the capacity to regulate emotions. However, studies have not directly tested whether vmHRV is associated with the ability to facially express emotions. In extending prior work, the current report tested links between resting vmHRV and the objectively assessed ability to facially express emotions, hypothesizing that higher vmHRV would predict greater expressive skill. Eighty healthy women completed self-reported measures, before attending a laboratory session in which vmHRV and the ability to express six emotions in the face were assessed. A repeated measures analysis of variance revealed a marginal main effect for vmHRV on skill overall; individuals with higher resting vmHRV were only better able to deliberately facially express anger and interest. Findings suggest that differences in resting vmHRV are associated with the objectively assessed ability to facially express some, but not all, emotions, with potential implications for health and well-being.

The association of resting state heart rate variability and 24-hour blood pressure variability in spinal cord injury.

Patients with high cervical complete spinal cord injuries (tetraplegia) sustain damage to the autonomic neural pathways that influence cardiovascular functioning and produce variability in the heart rate (HR) and blood pressure (BP). In non-injured individuals, an inverse relationship exists between resting autonomic control of the heart (as evidenced by HR variability (HRV)) and BP variability (BPV). This study examined the relationship between HRV, BP and BPV in individuals with tetraplegic (n=10) and paraplegic (n=10) spinal cord injuries, and a group of healthy controls (n=14). Resting HRV at baseline and 24-hour ambulatory BP measurements were collected from electrocardiogram measures of each participant. HRV was quantified using time- and frequency-domain measures. The standard deviation of the BP measurements was used as an index of BPV. Multivariate analyses of variance were performed to examine group differences for laboratory-based and 24-h dependent variables. The MANOVAs for HRV parameters (λ(14,50)=.352, p=.010, η(2)=.407) and for BP indices and HR (λ(16,48)=.318, p=.013, η(2)=.436) were significant. Furthermore, in line with existing evidence, we found that vagally mediated HRV was inversely related to BPV in healthy controls. However, this relationship did not hold for the tetraplegia group (ρ<|.42|), and mixed results were found for the paraplegia group (e.g., ρ<|.29| for time domain HRV, ρ>|.65| for low-frequency power). These results support the conclusion that the damage to the spinal sympathetic pathways to the heart found in people with tetraplegia causes a significant disruption in baroreflex control of BP.

Gender differences in the relationship between resting heart rate variability and 24-hour blood pressure variability.

The study explored the relationship between time- and frequency-domain indices of cardiac autonomic control and 24 h blood pressure variability (BPV) in a sample of healthy men and women. Vagally mediated cardiac control was inversely related to 24 h BPV, and measures of cardiac autonomic control were better predictors of systolic BPV in men and better predictors of diastolic BPV in women. These findings may help researchers to understand the disparity in cardiovascular disease morbidity and mortality between men and women.

Acute effects of BZP, TFMPP and the combination of BZP and TFMPP in comparison to dexamphetamine on an auditory oddball task using electroencephalography: a single-dose study.

RATIONALE: Piperazine-based designer drugs such as benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP) have been marketed and sold as legal alternatives to dexamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) until 2008 in New Zealand. When administered in combination, BZP + TFMPP have been reported to produce drug-drug synergism in rodents by stimulating the release of dopamine and serotonin. OBJECTIVES: This study was to evaluate the acute event-related potential effects of BZP, TFMPP or the combination of BZP + TFMPP compared with dexamphetamine in young healthy male adults. METHODS: A double-blind, randomised, placebo-controlled study investigated the effects of BZP, TFMPP, the combination of BZP + TFMPP, and dexamphetamine on the event-related potentials during an auditory oddball task. Healthy, right-handed males were given a single oral dose of either BZP (200 mg), TFMPP (60 mg), a combination of BZP + TFMPP (100/30 mg), dexamphetamine (20 mg) or placebo (lactose) and tested both before and 120 min after drug administration. RESULTS: A single dose of either TMFPP (t = -2.29, p = 0.03) or dexamphetamine (t = -2.33, p = 0.02) significantly reduced the P300 amplitude. A similar trend was also found in BZP. In contrast, BZP and TFMPP in combination has no effect. Neither P300 latency nor the mean reaction time was affected by any of the drug treatments. In addition, neither the P100 nor the P200 component was significantly affected following any of the drug treatments. CONCLUSIONS: A single oral dose of BZP or TFMPP, but not the combination of BZP/TFMPP, affected auditory sensory-evoked P300 potential in a manner similar to dexamphetamine.

Placebo 'serotonin' increases heart rate variability in recovery from psychosocial stress.

OBJECTIVE: To investigate placebo effects on heart rate (HR) and heart rate variability (HRV) in recovery from a psychosocial stressor. METHODS: A healthy sample underwent two mental arithmetic stress tests in one experimental session. After undergoing the baseline test, participants were randomized into control or placebo groups. Prior to the second stress test, the placebo group received an intranasal dose of 'serotonin' (placebo) with the suggestion that it would enhance recovery. HR and HRV were assessed throughout procedures. RESULTS: There was an increase in vagally-mediated HRV in the placebo group. The change in HR did not differ between groups. CONCLUSIONS: Placebo suggestion can enhance autonomic recovery after psychosocial stress. Findings are consistent with the notion of top-down mechanisms of placebo effects, but further research would need to specifically examine the role of top-down regulatory pathways as possible mediators of placebo-induced changes in autonomic function.

Ethnic differences in resting heart rate variability: a systematic review and meta-analysis.

BACKGROUND: Ethnic disparities in cardiovascular morbidity and mortality are widely documented in the literature. Recently, research has shown that decreased parasympathetic cardiac modulation is associated with the established and emerging risk factors for cardiovascular disease (CVD) and stroke. In consideration of the disproportionate CVD risk and disease profile of African Americans (AAs), it is plausible that decreased cardiac parasympathetic functioning may partially explain these disparities. In the present systematic review and meta-analysis, we assess the available evidence for a reliable ethnic difference in tonic vagally mediated heart rate variability (HRV), an indicator of parasympathetic cardiac modulation. METHODS: A systematic literature search was conducted yielding studies comparing tonic HRV in AAs and European Americans. Adjusted standardized effect sizes (Hedges g) were calculated using a mixed-effects model, with restricted maximum likelihood estimation for 17 studies containing appropriate measures of vagally mediated HRV. RESULTS: Meta-analysis results suggest that AAs have greater HRV than do European Americans (Hedges g = 0.93, 95% confidence interval = 0.25-1.62), even after consideration of several covariates including health status, medication use, and subgroup stratification by sex and age. CONCLUSIONS: These findings suggest that decreased vagally mediated HRV is not likely to account for the persistent health disparities experienced by AAs with respect to CVD risk and burden. These disparities underscore the need for continued research addressing socioethnic cardiovascular differences and the biobehavioral mechanisms involved.

Effects of exercise on the desire to smoke and physiological responses to temporary smoking abstinence: a crossover trial.

RATIONALE: Exercise has been shown to attenuate cigarette cravings during temporary smoking abstinence; however, the mechanisms of action are not clearly understood. OBJECTIVES: The objectives of the study were to compare the effects of three exercise intensities on desire to smoke and explore potential neurobiological mediators of desire to smoke. METHODS: Following overnight abstinence, 40 participants (25 males, 18-59 years) completed three 15 min sessions of light-, moderate-, or vigorous-intensity exercise on a cycle ergometer in a randomized crossover design. Ratings of desire to smoke were self-reported pre- and post-exercise and heart rate variability was measured throughout. Saliva and blood were analyzed for cortisol and noradrenaline in a sub-sample. RESULTS: Exercise influenced desire to smoke (F [2, 91] = 7.94, p < 0.01), with reductions greatest immediately after vigorous exercise. There were also significant time x exercise intensity interaction effects for heart rate variability and plasma noradrenaline (F [8, 72] = 2.23, p = 0.03), with a bias in noradrenaline occurring between light and vigorous conditions (adjusted mean difference [SE] = 2850 ng/ml [592], p < 0.01) at 5 min post-exercise. There was no interaction of time x exercise intensity for plasma and salivary cortisol levels. CONCLUSIONS: These findings support the use of vigorous exercise to reduce cigarette cravings, showing potential alterations in a noradrenergic marker.

Do slumped and upright postures affect stress responses? A randomized trial.

OBJECTIVE: The hypothesis that muscular states are related to emotions has been supported predominantly by research on facial expressions. However, body posture also may be important to the initiation and modulation of emotions. This experiment aimed to investigate whether an upright seated posture could influence affective and cardiovascular responses to a psychological stress task, relative to a slumped seated posture. METHOD: There were 74 participants who were randomly assigned to either a slumped or upright seated posture. Their backs were strapped with physiotherapy tape to hold this posture throughout the study. Participants were told a cover story to reduce expectation effects of posture. Participants completed a reading task, the Trier Social Stress speech task, assessments of mood, self-esteem, and perceived threat. Blood pressure and heart rate were continuously measured. RESULTS: Upright participants reported higher self-esteem, more arousal, better mood, and lower fear, compared to slumped participants. Linguistic analysis showed slumped participants used more negative emotion words, first-person singular pronouns, affective process words, sadness words, and fewer positive emotion words and total words during the speech. Upright participants had higher pulse pressure during and after the stressor. CONCLUSIONS: Adopting an upright seated posture in the face of stress can maintain self-esteem, reduce negative mood, and increase positive mood compared to a slumped posture. Furthermore, sitting upright increases rate of speech and reduces self-focus. Sitting upright may be a simple behavioral strategy to help build resilience to stress. The research is consistent with embodied cognition theories that muscular and autonomic states influence emotional responding.

Junior doctors in their first year: mental health, quality of life, burnout and heart rate variability.

There is a burgeoning interest in, and evidence of, quality of life and burnout issues among doctors. It was hypothesized that the junior doctors in this study would experience psychosocial and physiological changes over time, and that the obtained measures would indicate psychosocial and physiological anomalies. In addition, it was hypothesized that their psychosocial perceptions would be significantly associated with their physiological measures. A total sample of 17 junior doctors in their first year of training volunteered for this study. Over four time periods separated by 6 week phases, the doctors completed a set of quality of life and psychosocial inventories and wore a Polar RS800 Heart Rate Monitor over a day and night time interval. The findings showed that this sample of doctors did not report any problems associated with depression, anxiety, stress, burnout or quality of life (psychosocial measures). In addition, their heart rate variability scores (physiological measures) did not show any significant fluctuations. Furthermore, the responses from the self-report instruments measuring stress, anxiety, depression, quality of life and burnout did not consistently correlate with the HRV information suggesting a mind-body disconnection. More work needs to be done on larger samples to investigate these findings further given that the literature shows that junior doctors are likely to be stressed and working in stress-provoking environments.

Robots with display screens: a robot with a more humanlike face display is perceived to have more mind and a better personality.

It is important for robot designers to know how to make robots that interact effectively with humans. One key dimension is robot appearance and in particular how humanlike the robot should be. Uncanny Valley theory suggests that robots look uncanny when their appearance approaches, but is not absolutely, human. An underlying mechanism may be that appearance affects users' perceptions of the robot's personality and mind. This study aimed to investigate how robot facial appearance affected perceptions of the robot's mind, personality and eeriness. A repeated measures experiment was conducted. 30 participants (14 females and 16 males, mean age 22.5 years) interacted with a Peoplebot healthcare robot under three conditions in a randomized order: the robot had either a humanlike face, silver face, or no-face on its display screen. Each time, the robot assisted the participant to take his/her blood pressure. Participants rated the robot's mind, personality, and eeriness in each condition. The robot with the humanlike face display was most preferred, rated as having most mind, being most humanlike, alive, sociable and amiable. The robot with the silver face display was least preferred, rated most eerie, moderate in mind, humanlikeness and amiability. The robot with the no-face display was rated least sociable and amiable. There was no difference in blood pressure readings between the robots with different face displays. Higher ratings of eeriness were related to impressions of the robot with the humanlike face display being less amiable, less sociable and less trustworthy. These results suggest that the more humanlike a healthcare robot's face display is, the more people attribute mind and positive personality characteristics to it. Eeriness was related to negative impressions of the robot's personality. Designers should be aware that the face on a robot's display screen can affect both the perceived mind and personality of the robot.

The effect of anxiety on heart rate variability, depression, and sleep in chronic obstructive pulmonary disease.

OBJECTIVES: The current study investigates heart rate variability (HRV) responses to a psychosocial stressor in chronic obstructive pulmonary disease (COPD) patients, and the potential role of anxiety as a confounding factor in this relationship. Additionally, this study also investigates the influence of anxiety on sleep and depressive symptoms among COPD patients. METHODS: The study utilized a 2 (disease status)×2 (anxiety group) factorial design examining HRV associated with anxiety symptoms and COPD during a standardized acute social stress task. Participants (mean age 59.1±11.2 years; 50% female) completed pulmonary function testing, HRV monitoring, and self-report questionnaires assessing psychological factors. 30 COPD patients were age- and gender-matched with 30 healthy controls. RESULTS: HRV response to a psychosocial stressor among participants with higher anxiety (both COPD and healthy) reflected autonomic dysregulation in both time and frequency domains that was not evident among non-anxious participants. COPD participants with higher anxiety reported greater symptoms of depression and poorer sleep quality than did COPD participants with low anxiety. CONCLUSIONS: Anxiety is associated with dysregulated HRV response to a psychosocial stressor, but the negative influence of anxiety and COPD on autonomic function did not appear to be additive. Comorbid anxiety in patients with COPD is associated with increased behavioral and psychological symptoms of distress.

Expectation and the placebo effect in inflammatory skin reactions: a randomised-controlled trial.

OBJECTIVE: This study investigated the placebo effect on experimentally induced skin reactions via the manipulation of expectation. METHODS: Fifty-eight healthy volunteers were randomised into either expectancy or control groups. All participants received a baseline administration of histamine on one arm (Time 1), then a second administration on the other arm, approximately 30 minutes later (Time 2). Prior to the second administration, the expectancy group was told that an antihistamine cream (the placebo) had been applied that would reduce their skin reaction to the histamine. Expected wheal area, actual wheal area, heart rate, and heart rate variability were measured at each time point. RESULTS: There was a positive relationship between expected and actual wheal area at Time 1. While the expectancy group expected a smaller skin reaction on the second arm they did not experience a greater reduction in wheal area, compared to control. The expectancy group had a greater reduction in heart rate during the second skin reaction, after the manipulation of expectation (p<.05). CONCLUSION: While wheal area was not modulated, it may be worth further investigating this possibility, with modifications to the protocol. The reduction of heart rate appears to be an expectation effect and future research could elucidate mechanisms involved. There is an indication that expectations and inflammatory skin reactions are associated. Further study might aim to clarify the direction and nature of this relationship.

The Relationship between Heart Rate Variability and Adiposity Differs for Central and Overall Adiposity.

While frank obesity is associated with reduced HRV, indicative of poorer autonomic nervous system (ANS) function, the association between body mass index (BMI) and HRV is less clear. We hypothesized that effects of adiposity on ANS are mostly mediated by visceral fat and less by subcutaneous fat; therefore, centrally distributed adipose tissue, that is, waist circumference (WC), should be more strongly associated with HRV than overall adiposity (BMI). To examine this hypothesis, we used data collected in a subset of the Baltimore Longitudinal Study of Aging to compare strength of association between HRV and WC to that of HRV and BMI. Time domain HRV variables SDNN (standard deviation of successive differences in normal-to-normal (N-N) intervals) and RMSSD (root mean square of successive differences in N-N intervals) were calculated from 24-hour Holter recordings in 159 participants (29-96 years). Increasing WC was associated with decreasing SDNN and RMSSD in younger but not older participants (P value for WC-by-age interaction = 0.003). BMI was not associated with either SDNN or RMSSD at any age. In conclusion, central adiposity may contribute to sympathetic and parasympathetic ANS declines early in life.

A meta-analysis of heart rate variability and neuroimaging studies: implications for heart rate variability as a marker of stress and health.

The intimate connection between the brain and the heart was enunciated by Claude Bernard over 150 years ago. In our neurovisceral integration model we have tried to build on this pioneering work. In the present paper we further elaborate our model and update it with recent results. Specifically, we performed a meta-analysis of recent neuroimaging studies on the relationship between heart rate variability and regional cerebral blood flow. We identified a number of regions, including the amygdala and ventromedial prefrontal cortex, in which significant associations across studies were found. We further propose that the default response to uncertainty is the threat response and may be related to the well known negativity bias. Heart rate variability may provide an index of how strongly 'top-down' appraisals, mediated by cortical-subcortical pathways, shape brainstem activity and autonomic responses in the body. If the default response to uncertainty is the threat response, as we propose here, contextual information represented in 'appraisal' systems may be necessary to overcome this bias during daily life. Thus, HRV may serve as a proxy for 'vertical integration' of the brain mechanisms that guide flexible control over behavior with peripheral physiology, and as such provides an important window into understanding stress and health.