The extent to which variation in posture and respiration can confound pre-ejection period and respiratory sinus arrhythmia (RSA) as indices of cardiac sympatho-vagal activity was examined. Within-subjects changes in these measures were assessed in 36 subjects during different postures and (paced) respiratory frequencies. Changes from supine to sitting to standing led to reduced RSA values and longer pre-ejection periods, reflecting the known decrease in vagal but not the increase of sympathetic activity. Multilevel path analysis showed that within-subjects changes in sympatho-vagal balance were faithfully reflected by changes in interbeat interval, but imperfectly by changes in RSA and pre-ejection period. It was concluded that pre-ejection period should be stratified for posture and RSA for respiratory frequency to reliably index changes in sympatho-vagal balance when these factors are prone to change (e.g., during 24-h ambulatory recording)

This study examined physiological effects of separation and reunion in a sample 3- to 6-year-old children. Using continuous ambulatory recording, changes in heart rate (HR), respiratory sinus arrhythmia (RSA), and pre-ejection period (PEP) were compared across the episodes of a separation–reunion procedure based on the strange situation. RSA decreased significantly over the course of the procedure as well as on separation from the parent and not the stranger, supporting that separation from the attachment figure elicited vagal withdrawal in young children. The absence of significant PEP effects suggest that the separation–reunion procedure, and more specifically separation from the parent, was not threatening enough to activate the sympathetic nervous system, even if children were insecure attached and inhibited with regard to strangers. Some of the variability in HR increases to reunion was explained by younger age. The findings highlight the role of the ANS as a regulatory process in the parent–child relationship. © 2007 Wiley Periodicals, Inc. Dev Psychobiol 49: 119–128, 2007.

The relationships between road and rail traffic noise with pre-ejection period (PEP) and with respiratory sinus arrhythmia (RSA) during sleep, as indices of cardiac sympathetic and parasympathetic nervous system tone, were investigated in the field (36 subjects, with 188 and 192 valid subject nights for PEP and RSA, respectively). Two analyses were conducted. The first analysis investigated the overall relationships across the entire sleep period. A second analysis investigated differences in the relationships between the first and second halves of the sleep period. Separate multilevel linear regression models for PEP and RSA were employed. Potential covariates for each model were selected from the same pool of variables, which included: gender, age, body-mass index, education level, traffic noise source type, intake of medication, caffeine, alcohol and cigarette smoke, and hindrance during sleep due to the ambulatory recordings. RSA models were adjusted for respiration rate. Mean indoor traffic noise exposure was negatively related to mean RSA during the sleep period, specifically during the second half of the sleep period. Both respiration rate and age were negatively associated with RSA. No significant relationships were observed for PEP. The results indicate that higher indoor traffic noise exposure levels may lead to cardiac parasympathetic withdrawal during sleep, specifically during the second half of the sleep period. No effect of indoor traffic noise on cardiac sympathetic tone was observed.

The current study examined mean level and change in extraversion and neuroticism across adolescence in relation to physiological stress reactivity to social evaluation. Adolescents (n=327) from the Dutch general population reported on personality measures at five annual assessments. At age 17 years, adolescents participated in a psychosocial stress procedure characterized by social evaluation during which cortisol, heart rate, pre-ejection period (PEP) and heart rate variability were assessed. Dual latent growth curve models were fitted in which the intercepts (mean level) and slopes (change) of personality across adolescence predicted the intercepts (baseline) and slopes (reactivity) of the physiological stress measures. Most comparisons revealed no relation between personality and stress reactivity. Adolescents with higher mean level scores on extraversion did show lower cortisol reactivity. Adolescents with higher mean level neuroticism scores showed higher PEP reactivity. Our findings lend partial support for a relation between personality and physiological stress reactivity.

This laboratory study explored buffering and recovery effects of viewing urban green and built spaces on autonomic nervous system activity. Forty-six students viewed photos of green and built spaces immediately following, and preceding acute stress induction. Simultaneously recorded electrocardiogram and impedance cardiogram signal was used to derive respiratory sinus arrhythmia (RSA) and pre-ejection period (PEP), indicators of respectively parasympathetic and sympathetic activity. The findings provide support for greater recovery after viewing green scenes, as marked by a stronger increase in RSA as a marker of parasympathetic activity. There were no indications for greater recovery after viewing green scenes in PEP as a marker of sympathetic activity, and there were also no indications of greater buffering effects of green space in neither RSA nor PEP. Overall, our findings are consistent with a predominant role of the parasympathetic nervous system in restorative effects of viewing green space.

In the current study, the role of pre-ejection period (PEP) and respiratory sinus arrhythmia (RSA) was studied in the association between prior adversities and antisocial behavior in adolescence. PEP and RSA task reactivity and recovery to a public speaking task were assessed in adolescents from a longitudinal population-based study (N=624, Mage=16.14 years, 49.2% boys). Perinatal adversities were unrelated to antisocial behavior, but experiencing more stressful adversities between age 0 and 15 was associated with antisocial behavior at age 16 in boys with blunted PEP reactivity and smaller PEP differences from rest to recovery. Number of adversities between age 0 and 15 was associated with antisocial behavior in boys with blunted and girls with heightened RSA reactivity and larger PEP differences from rest to recovery. The association between prior adversities and antisocial behavior were small in effect size and depended upon sex and PEP and RSA reactivity and recovery.

Exposure to prenatal adversity is associated with aggression later in life. Individual differences in autonomic nervous system (ANS) functioning, specifically nonreciprocal activation of the parasympathetic (PNS) and sympathetic (SNS) nervous systems, increase susceptibility to aggression, especially in the context of adversity. Previous work examining interactions between early adversity and ANS functioning in infancy is scarce and has not examined interaction between PNS and SNS. This study examined whether the PNS and SNS moderate the relation between cumulative prenatal risk and early physical aggression in 124 children (57% male). Cumulative risk (e.g., maternal psychiatric disorder, substance (ab)use, and social adversity) was assessed during pregnancy. Parasympathetic respiratory sinus arrhythmia (RSA) and sympathetic pre-ejection period (PEP) at baseline, in response to and during recovery from emotional challenge were measured at 6 months. Physical aggression and non-physical aggression/oppositional behavior were measured at 30 months. The results showed that cumulative prenatal risk predicted elevated physical aggression and non-physical aggression/oppositional behavior in toddlerhood; however, the effects on physical aggression were moderated by PNS and SNS functioning. Specifically, the effects of cumulative risk on physical aggression were particularly evident in children characterized by low baseline PNS activity and/or by nonreciprocal activity of the PNS and SNS, characterized by decreased activity (i.e., coinhibition) or increased activity (i.e., coactivation) of both systems at baseline and/or in response to emotional challenge. These findings extend our understanding of the interaction between perinatal risk and infant ANS functioning on developmental outcome.

Introduction
Stroke volume (SV) and cardiac output are important measures in the clinical evaluation of cardiac patients and are also frequently used in research applications. This study was aimed to improve SV scoring derived from spot-electrode based impedance cardiography (ICG) in a pediatric population of healthy volunteers and patients with a corrected congenital heart defect.
Methods
128 healthy volunteers and 66 patients participated. First, scoring methods for ambiguous ICG signals were optimized to improve agreement of B- and X-points with aortic valve opening/closure in simultaneously recorded transthoracic echocardiography (TTE). Building on the improved scoring of B- and X-points, the Kubicek equation for SV estimation was optimized by testing the agreement with the simultaneously recorded SV by TTE. Both steps were initially done in a subset of the sample of healthy children and then validated in the remaining subset of healthy children and in a sample of patients.
Results
SV assessment by ICG in healthy children strongly improved (intra class correlation increased from 0.26 to 0.72) after replacing baseline thorax impedance (Z0) in the Kubicek equation by an equation (7.337–6.208∗dZ/dtmax), where dZ/dtmax is the amplitude of the ICG signal at the C-point. Reliable SV assessment remained more difficult in patients compared to healthy controls.
Conclusions
After proper adjustment of the Kubicek equation, SV assessed by the use of spot-electrode based ICG is comparable to that obtained from TTE. This approach is highly feasible in a pediatric population and can be used in an ambulatory setting.

Men who misuse alcohol tend to experience negative affect, which may entail difficulties in regulating emotions to cope effectively with stressful or anxiety-provoking situations, thus increasing the risk of alcohol relapse. This dysphoric state has been associated with alexithymia, which compromises an individual’s abilities to acknowledge, recognize, and regulate emotional states. A physiological correlate of emotional regulation is autonomic flexibility, as shown by emotional dysregulation in men who misuse alcohol being correlated with reduced parasympathetic activation to control heart rate variability during stress and/or conflict situations. Hence, the main aim of this study was to investigate whether long-term abstinent alcoholic (LTAA) men exhibit higher levels of negative affect and sympathetic activation (cardiovascular and electrodermal) in response to acute standardized laboratory stress than non-alcoholic controls. In addition, we hypothesized that the higher the alexithymic traits, the greater would be the increase in negative affect and sympathetic activation in response to stress, especially in LTAAs. Our data demonstrated that LTAAs experienced slightly greater increases in anxiety, states of anger, and worsening of mood than controls. Moreover, they exhibited lower high-frequency heart rate variability, respiratory sinus arrhythmia values, shorter pre-ejection periods, and higher respiratory rates than controls. Finally, alexithymic traits imply greater worsening of mood and sympathetic predominance (shorter pre-ejection periods and smaller magnitude of response), with the associations being stronger in LTAAs. These findings indicate a different emotional and cardiovascular response to psychosocial stress in LTAA than non-alcoholic men. Improving our knowledge of the way this population reacts to stress may help identify risk factors for alcohol relapse.

Although emotional responses are theorized to be important in the development of empathy, findings regarding the prediction of early empathic behavior by infant behavioral and physiological responses are mixed. This study examined whether behavioral and physiological responses to mild emotional challenge (still face paradigm and car seat task) in 118 infants at age 6 months predicted empathic distress and empathic concern in response to an empathy-evoking task (i.e, experimenter’s distress simulation) at age 20 months. Correlation analyses, corrected for sex and baseline levels of physiological arousal, showed that stronger physiological and behavioral responses to emotional challenge at age 6 months were positively related to observed empathic distress, but not empathic concern, at age 20 months. Linear regression analyses indicated that physiological and behavioral responses to challenge at 6 months independently predicted empathic distress at 20 months, which suggests an important role for both physiological and behavioral emotional responses in empathy development. In addition, curvilinear regression analyses showed quadratic associations between behavioral responses at 6 months, and empathic distress and empathic concern at 20 months, which indicates that moderate levels of behavioral responsivity predict the highest levels of empathic distress and empathic concern.