Measures Of Respiratory Sinus Arrhythmia Research Articles

Physiological and Family-Level Correlates of Autistic Adolescents' Sleep Quality.

Autistic adolescents commonly experience sleep-related difficulties and prior studies have sought to separately examine physiological and family-level predictors of their sleep quality. The current study aimed to conceptually replicate and extend to an adolescent sample a prior study that found respiratory sinus arrhythmia was associated with sleep quality in autistic children. In addition, the current study also examined whether the quality of the family environment was associated with sleep quality in autistic adolescents. The sample consisted of 107 autistic adolescents who completed a baseline measure of respiratory sinus arrhythmia and then watched a video of their parents engaged in a discussion about a topic of disagreement while their respiratory sinus arrhythmia reactivity was measured. Adolescents also completed questionnaires measuring their sleep quality and family environment. In regression models, adolescents' physiological functioning was not a significant predictor of their sleep quality; however, adolescents living in poorer quality family environments reported worse sleep quality after controlling for their physiological functioning. The interaction between physiological functioning and the family environment predicting sleep quality was non-significant. Although the current study did not conceptually replicate prior work, the findings highlight the importance of the family environment for adolescents' sleep. Implications and future directions are discussed.

ВЛИЯНИЕ ПРОЦЕССА ЖЕВАНИЯ НА РЕСПИРАТОРНУЮ СИНУСОВУЮ АРИТМИЮ

Respiratory sinus arrhythmia (RSA) is a clockwise fluctuation in heart rate at the frequency of the respiratory cycle. RSA is an important homeostatic mechanism, the parameters of which change under various conditions - from stress to physical exercise. However, the direct effect of chewing, the most common form of muscle activity, on RSA has not yet been studied. We studied the dynamic evolution of RSA and the associated heart rate and respiratory rate during the transition from rest to chewing gum in 37 students (15 men). The measure of RSA in this study was the spectral power of high-frequency HF oscillations. Chewing was accompanied by a slight increase in respiratory rate (RR) and a significant increase in heart rate (HR), but a statistically insignificant increase in the HR/HR ratio. Although respiration was an important determinant of RSA in this study, we observed a significant decrease in HF in the presence of relatively stable RR and HR/RR levels, indicating that the main driver of the evolution of RSA during mastication is an increase in sympathetic tone due to the trigeminal reflex.

Associations between physical activity and autonomic function during deep breathing test: the Swedish CArdioPulmonary bioImage Study (SCAPIS).

The deep breathing test (DBT) is a sensitive test of cardiovagal function. The aim of this study was to explore associations between physical activity and sedentary time, measured by accelerometer, and autonomic function, using DBT. In the Swedish Cardio-Pulmonary bioImage Study, men and women aged 50-64 were randomly invited from the general population. A total of 4325 subjects who underwent DBT and assessment of physical activity and sedentary time by accelerometery were included. ECG files from 1-min DBT were used to calculate measures of respiratory sinus arrhythmia [RSA; expiration-inspiration (E-I) difference and E/I ratio], heart rate variability [HRV; root mean square of successive differences (RMSSD), standard deviation of heart rates and mean circular resultant]. Low RSA and HRV was defined as the lowest 10% in the population. For accelerometer-assessed physical activity, there were significant associations between high percentage of sedentary time and low E/I (p < 0.01), and low RMSSD (p < 0.01) in an age- and sex-adjusted model, and between percentage of sedentary time and low RMSSD (p = 0.04) in a risk factor-adjusted model. Low RMSSD was less common in those with a high percentage of moderate to vigorous physical activity (p = 0.04, after risk-factor adjustment). These associations became non-significant when further adjusting for heart rate. We report associations between degree of physical activity and indices of autonomic dysfunction in a large population. The relationships were no longer significant after adjustments for heart rate, indicating that the relationship between physical activity and cardiovagal function partly is accounted for by reduced heart rate.

Resting respiratory sinus arrhythmia is related to emotion reactivity to social-evaluative stress

BackgroundHigher resting parasympathetic nervous system activity, as indexed by respiratory sinus arrhythmia (RSA), has been considered a marker of emotion regulatory capacity and is consistently related to better mental health. However, it remains unclear how resting RSA relates to emotion reactivity to acute social-evaluative stress, a potent predictor of depression and other negative outcomes. MethodA sample of 89 participants (Mage = 18.36, SD = 0.51; 58.43 % female) provided measures of RSA at rest and then completed the Trier Social Stress Test, a standardized laboratory-based social-evaluative stress task that involves public speaking and mental arithmetic while being evaluated by two confederate judges. Participants reported a variety of emotions (e.g., negative emotion, positive emotion) at baseline and immediately after the stress task. ResultsParticipants with higher resting RSA showed greater increases in negative emotion, guilt, depressive emotion, and anger, as well as greater decreases in positive emotion after the task. LimitationData were limited to a relatively small sample of late adolescents, who may be particularly responsive to social-evaluative stress compared to adults. ConclusionsFindings suggest that higher resting RSA may enhance emotion responses to social-evaluative stress in adolescents, potentially due to active engagement and responding to rather than passively viewing stimuli. Higher resting RSA may promote flexible emotion responses to the social environment, which may account for associations between higher RSA and better mental health.

Close TIES in relationships: A dynamic systems approach for modeling physiological linkage

We explore complex dynamic patterns of autonomic physiological linkage (i.e., statistical interdependence of partner’s physiology; PL), within the sympathetic and parasympathetic nervous systems (SNS and PNS), as potential correlates of emotional and regulatory dynamics in close relationships. We include electrodermal activity (EDA) as an indicator of SNS activation and respiratory sinus arrhythmia (RSA) as an indicator of regulatory and/or homeostatic processes within the PNS. Measures of EDA and RSA were collected in 10-second increments from 53 heterosexual couples during a mixed-emotion conversation in the laboratory. We used the R statistical package, rties (Butler &amp; Barnard, 2019), to model the dynamics of EDA and RSA with a coupled oscillator model and then categorized couples into qualitatively distinct profiles based on the set of parameters that emerged. We identified two patterns for EDA and three patterns for RSA. We then investigated associations between the PL patterns and self-report measures of relationship and conversation quality and emotional valence using Bayesian multilevel and logistic regression models. Overall, we found robust results indicating that PL profiles were credibly predicted by valence and relationship quality reported prior to the conversations. In contrast, we found very little evidence suggesting that PL patterns predict self-reported conversation quality or valence following the conversation. Together, these results suggest that PL across autonomic subsystems may reflect different processes and therefore have different implications when considering interpersonal dynamics.

Associations between infant-mother physiological synchrony and 4- and 6-month-old infants' emotion regulation.

In this study we assessed whether physiological synchrony between infants and mothers contributes to infants' emotion regulation following a mild social stressor. Infants between 4 and 6 months of age and their mothers were tested in the face-to-face-still-face paradigm and were assessed for behavioral and physiological self-regulation during and following the stressor. Physiological synchrony was calculated from a continuous measure of respiratory sinus arrhythmia (RSA) enabling us to cross-correlate the infants' and mothers' RSA responses. Without considering physiological synchrony, the evidence suggested that infants' distress followed the prototypical pattern of increasing during the Still Face episode and then decreasing during the reunion episode. Once physiological synchrony was added to the model, we observed that infants' emotion regulation improved if mother-infant synchrony was positive, but not if it was negative. This result was qualified further by whether or not infants suppressed their RSA response during the Still Face episode. In sum, these findings highlight how individual differences in infants' physiological responses contribute significantly to their self-regulation abilities.

Biological signatures of emotion regulation flexibility in children: Parenting context and links with child adjustment.

Emotion regulation (ER) is a key facet of positive adjustment throughout the lifespan. Recent theoretical and empirical innovations suggest that current methods for assessing ER are limited, because they measure discrete strategy use instead of ER flexibility and are insensitive to ecologically valid social contexts that influence ER. This is particularly important for studying the impact of parenting on ER development during childhood. The current study (N = 93; 47 females; Mage = 6.98, SD = 1.12) examined child ER flexibility during a directed reappraisal task (DRT) with two parenting contexts: passive parent presence or active scaffolding. Two biological signatures of ER flexibility were measured: respiratory sinus arrhythmia (RSA), an index of physiological flexibility; and the late positive potential (LPP), an index of neurocognitive flexibility. Emotion regulation behavior was observed during a frustrating wait, and parents reported on child ER and adjustment. Greater ER flexibility indexed via the LPP and RSA both predicted observed ER during the frustrating wait, but only RSA predicted parent-reported trait ER and fewer adjustment problems. Emotion regulation flexibility indexed by the LPP was bolstered by parent presence and scaffolding of child ER during the DRT, but RSA measures were not sensitive to parenting context. Taken together, the results provide converging evidence for the conceptualization of ER in terms of physiological and neurocognitive flexibility in childhood. Furthermore, among school-aged children, while physiological flexibility broadly predicted parent-reported child adjustment, neurocognitive flexibility may be context-sensitive and predictive of concurrent observed ER.

The impact of self-reported levels of anxiety on respiratory sinus arrhythmia levels in adults who stutter

PurposeThis study investigated whether subjective levels of anxiety predict respiratory sinus arrythmia (RSA) levels in adults who stutter (AWS) compared to (ANS) during baseline and social stress situations. MethodsParticipants were eight AWS and 10 ANS who performed a modified version of the Trier Social Stress Test (TSST-M). For this, participants were required to prepare and deliver a 5-minute speech and perform a nonword reading task in front of what was perceived as a group of professionals trained in public speaking. Measures of respiratory sinus arrhythmia (RSA) were calculated for baseline and TSST-M conditions. Participants also completed the State-Trait Anxiety Inventory (STAI), both the trait (STAI-T) and state (STAI-S) portion, which served as subjective anxiety ratings. Univariate analyses of variances (UNIANOVA) were used to assess the effects of the STAI-T and STAI-S anxiety on respiratory sinus arrhythmia (RSA) levels at pre-stress and TSST-M conditions. RSA, an index of parasympathetic nervous system activity, is considered to be a measure of emotional regulation. The strength of the effects of STAI-T and STAI-S on RSA levels was evaluated with the unstandardized coefficients for each group separately. ResultsResults showed a significant difference between groups for the effects of STAI-T on RSA values for the pre-stress nonword reading task. No other significant differences were found between groups for the pre-stress or TSST-M conditions. Slope estimates showed that STAI-T was a significant predictor of RSA values for pre-stress speaking conditions for the AWS but not ANS. No significant fixed effects or interaction effects were found for the STAI-S and RSA levels in the AWS or ANS. Nor were there significant effects of STAI-T on RSA levels in the AWS or ANS for TSST-M conditions. Descriptive analysis revealed the effects found in the AWS during pre-stress conditions were attributed to a subgroup of AWS who reported low self-reports of anxiety (i.e. STAI-T) and high levels of emotional regulation (i.e. RSA) across social stress conditions. DiscussionLow self-reported STAI-T scores simultaneous with high RSA levels in some AWS may reflect a self-regulatory strategy adapted in response to chronic, daily stress associated with stuttering.

Physiological and social synchrony as markers of PTSD and resilience following chronic early trauma.

Although resilience is a key topic in clinical theory and research, few studies focused on biobehavioral mechanisms that underpin resilience. Guided by the biobehavioral synchrony frame, we examined the dynamic interplay of physiological and behavioral synchrony as marker of risk and resilience in trauma-exposed youth. A unique cohort of war-exposed versus control children was followed at four time-points from early childhood to preadolescence and child posttraumatic stress disorder (PTSD) repeatedly assessed. At preadolescence (11-13 years), mother and child were observed in several social and nonsocial tasks while cardiac data collected and measures of respiratory sinus arrhythmia (RSA) and RSA synchrony computed. The social interactive task was microcoded for behavioral synchrony and the second-by-second balance of behavioral and physiological synchrony was calculated. War-exposed preadolescents were divided into those diagnosed with PTSD at any time-point across childhood versus resilient children. Group differences in behavioral synchrony, RSA synchrony, and their interplay emerged. PTSD dyads exhibited the tightest autonomic synchrony combined with the lowest behavioral synchrony, whereas resilient dyads displayed the highest behavioral and lowest autonomic synchrony. Hierarchical Linear Model analysis pinpointed two resilience-promoting mechanisms. First, for resilient and control dyads, moments of behavioral synchrony were coupled with decreased RSA synchrony. Second, only among resilient dyads, moments of behavioral synchrony increased child RSA levels. Findings specify mechanisms by which biobehavioral synchrony promotes resilience. As children grow, the tightly coupled mother-child physiology must be replaced by loosely coordinated behavioral attunement that buttresses maturation of the child's allostatic self-regulation. Our findings highlight the need for synchrony-based interventions to trauma-exposed mothers.

Distribution, Stability, and Continuity of Autonomic Nervous System Responsivity at 18- and 36-Months of Age.

Cardiac autonomic nervous system (ANS) measures, respiratory sinus arrhythmia (RSA) and preejection period (PEP), are valid and reliable indicators of children's sensitivity to their environment; however, there are few studies of ANS measures in children less than three years of age. This study's aim was to summarize the distributions, stability, and continuity of RSA and PEP measures during resting, challenge, and reactivity for children at 18- and 36-months. This was a cohort study of racially- and ethnically-diverse, low-income children who completed a developmentally challenging protocol while we simultaneously assessed their RSA and PEP at 18-months (N = 134) and 36-months (N = 102). The ANS resting, challenge, and reactivity measures at 18- and 36-months of age were normally distributed. The RSA resting (r = 0.29), RSA challenge (r = 0.44), PEP resting (r = 0.55) and PEP challenge (r = 0.58) measures were moderately stable but RSA (r = 0.01) and PEP reactivity (r = 0.02) were not stable from 18- to 36-months of age. There was no continuity in the ANS measures from 18- to 36-months of age with statistically significant changes in sample means for all of the ANS measures. These developmental changes in ANS are shown at the sample level but there are individual differences in ANS responses from 18- to 36-months that may be affected by adversity or protective factors experienced early in life.

Quantifying the dynamic nature of vagal responsivity in infancy: Methodological innovations and theoretical implications.

According to polyvagal theory, rapid modulation of the vagal brake develops early in infancy and supports social interactions. Despite being viewed as a dynamic system, researchers typically assess vagal regulation using global measures of respiratory sinus arrhythmia (RSA; an index of vagal tone). This study sought to capture the dynamic property of RSA and evaluate individual differences in within-infant RSA responsivity during mother-infant interaction. RSA was evaluated in a sample of 135 6-month-old Mexican-American infants during a 5-min free play task. Mothers reported on their children's behavioral problems and competence at 18months using the Brief Infant-Toddler Social and Emotional Assessment. Time-varying estimates of infant RSA during the interaction were obtained using a multiple window technique and spectrogram analysis. Using structural equation modeling, we evaluated whether within-infant SD of RSA predicted infants' behavioral problems and competence at 18months, after adjusting for infants' mean RSA and covariates. Greater within-infant SD of RSA predicted more behavior problems at 18months. This study demonstrates that assessing intra-individual variability in RSA, or the extent to which infants fluctuate around their average level of RSA during a task, enhances our ability to test polyvagal theory's central tenet: vagal regulation supports well-regulated social interaction.

Autonomic complexity and emotion (dys-)regulation in early childhood across high- and low-risk contexts.

Developing the ability to regulate one's emotions in accordance with contextual demands (i.e., emotion regulation) is a central developmental task of early childhood. These processes are supported by the engagement of the autonomic nervous system (ANS), a physiological hub of a vast network tasked with dynamically integrating real-time experiential inputs with internal motivational and goal states. To date, much of what is known about the ANS and emotion regulation has been based on measures of respiratory sinus arrhythmia, a cardiac indicator of parasympathetic activity. In the present study, we draw from dynamical systems models to introduce two nonlinear indices of cardiac complexity (fractality and sample entropy) as potential indicators of these broader ANS dynamics. Using data from a stratified sample of preschoolers living in high- (i.e., emergency homeless shelter) and low-risk contexts (N = 115), we show that, in conjunction with respiratory sinus arrhythmia, these nonlinear indices may help to clarify important differences in the behavioral manifestations of emotion regulation. In particular, our results suggest that cardiac complexity may be especially useful for discerning active, effortful emotion regulation from less effortful regulation and dysregulation.

Resting respiratory sinus arrhythmia and posttraumatic stress disorder: A meta-analysis

Respiratory sinus arrhythmia (RSA) has been examined as a psychophysiological marker of stress vulnerability. Research indicates that low resting RSA is associated with physical and mental health problems, including posttraumatic stress disorder (PTSD). Some research suggests that people diagnosed with PTSD have lower RSA than people without PTSD, but findings have been mixed and the overall magnitude of this effect is unknown, indicating the need for a comprehensive meta-analysis. This meta-analysis examined the association between PTSD and baseline RSA in 55 studies, including 12 unpublished studies, with a total sample size of 6689. Studies were included if they used a PTSD measure, a baseline measure of RSA, and involved humans. Studies were excluded if they were not available in English, did not present quantitative data, presented duplicate data, were a case series, or did not provide results required for computing an effect size. The meta-analysis indicated there is a small but significant association between PTSD and RSA (g = −0.26; 95% CI = −0.35, −0.16) with moderate heterogeneity. Moderator analyses suggested that effects are larger for adults than for children and for DSM-5 PTSD measures than for non-DSM referenced measures. We found some evidence for publication bias among the meta-analysis findings. Overall, there is a small but reliable association between PTSD and lower resting RSA, providing support for further research examining the complex relationship between parasympathetic activity and PTSD.

Short-Term Test-Retest Reliability of Respiratory Sinus Arrhythmia (RSA) in Young Adults

Abstract. Despite the burgeoning use of respiratory sinus arrhythmia (RSA), heart period (HP), and blood pressure (BP) to study individual differences in autonomic regulatory processes in young adults, few studies have examined the short-term reliability of such autonomic measures in emerging adulthood. If resting autonomic measures indeed reflect “trait-like” individual differences, they should have acceptable levels of test-retest reliability. We examined the 1-month test-retest reliability of resting measures of RSA as well as HP, systolic (SBP) and diastolic blood pressure (DBP) in a sample of 41 healthy young adults. Test-retest reliability of all four measures was good-to-excellent across the 1-month period. However, uncontrolled mean RSA declined from Time 1 to Time 2, suggesting that while individual differences in RSA were stable, mean RSA appeared to be sensitive to condition effects. Even with random variation, all of these measures were stable across one month, demonstrating acceptable short-term test-retest reliability in emerging adulthood.

Can Daytime Measures of Respiratory Sinus Arrhythmia and Breathing Stability Serve as Biomarkers for OSA?

Obstructive sleep apnea (OSA) is by definition a disorder of nighttime breathing however, there is good evidence that impairments in cognitive and cardiovascular function persist in the day and that adults with OSA exhibit daytime CO2 retention and hypoxemia. Although a diagnosis of OSA requires in‐home or in‐laboratory overnight polysomnography, these types of tests are expensive and, due to health insurance quotas, may be limited in availability. Here, we outline simple methods for assessing daytime respiratory sinus arrhythmia (RSA) and respiratory stability that show promise as potential diagnostic tools to identify adults at risk for OSA. We recorded heart rate (finger oxy‐photoplethysmography) and respiration (inductance plethysmography) in adults with obstructive sleep apnea (N=6) and age and BMI matched healthy adults (N=8). Subjects completed five minutes of eupneic breathing, five minutes of paced breathing (7.5 breaths/minute) and after equilibration, five minutes of hyperoxic, hypercapnia (5% FICO2). Using de‐identified data, we obtained estimates of RSA amplitude, RSA stability, and respiratory stability for each subject in each condition and performed a regression analysis to determine the relationship between each of these variables and subjects' apnea hypopnea index (0–25 AHI). Our preliminary results indicate that daytime measures of respiratory stability and RSA can differentiate healthy adults from adults diagnosed with OSA (p&lt;0.006). Importantly, the analysis requires minimal instrumentation and short sampling periods (~5 minutes). Summary schematics arising from the analysis may prove useful as preliminary clinical/diagnostic biomarkers of RSA and cardio‐respiratory coupling in adults at risk for OSA.Support or Funding InformationThis work was supported by start‐up monies (Department of Physiology, University of Arizona) awarded to EFB and by The Finley and Florence Brown Predoctoral Fellowship (Sarver Heart Center, University of Arizona) awarded to JRV.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Respiratory sinus arrhythmia: Modeling longitudinal change from 6 weeks to 2 years of age among low‐income Mexican Americans

Parasympathetically-mediated heart rate variability (HRV), commonly indexed via respiratory sinus arrhythmia (RSA), is theorized to support the physiological regulation of emotion; however, little is known about the trajectory of change in resting RSA across early development among high-risk populations for whom emotion regulation is crucial. This study characterized resting RSA change from 6 weeks to 2 years of age among 312 low-income Mexican American infants. RSA was assessed longitudinally at 6, 12, 18, 24, 52, 78, and 104 weeks of age. On average, resting RSA increased as infants aged, and this change accelerated over time. There was significant variance between infants in resting RSA at 6 weeks of age, and in the slope, and acceleration of resting RSA change. Intraclass correlation among infants' resting RSA measures was minimal, indicating that resting RSA may not be "trait-like" during infancy. Results characterize early RSA development among a high-risk sample, which can inform theoretical understanding of the development of emotional, and behavioral self-regulation in a high-risk population, as well as efforts to promote wellbeing across early childhood.

Attachment and telomere length: more evidence for psychobiological connections between close relationships, health, and aging.

Individuals with a history of poor interpersonal relationships are more likely to demonstrate negative health outcomes than those who have had high quality relationships. We sought to evaluate how attachment orientations, stress-induced respiratory sinus arrhythmia (RSA), and self-reported stress were associated with length of telomeres measured from peripheral blood mononuclear cells. Participants (N=213) completed self-report measures of attachment and stress. Measurement of RSA was conducted before and after a stressful task and a blood draw was completed for analysis of telomere length. Attachment orientations were not directly associated with telomere length; however, we found that high attachment anxiety was associated with shorter length of telomeres via high self-reported stress. Attachment avoidance was also associated with telomere length via self-reported stress, but only among those with high stress-induced RSA. Exploratory analyses of T cell subsets indicated that stress was most strongly associated with telomeres from CD8CD28+ cells in comparison to CD8CD28- and CD4 cells. Study findings indicate that attachment orientations are associated with telomere length via stress, providing novel insights into the mechanisms through which close relationships can impact health and aging.

Externalizing Behavior in at-Risk Preadolescents: Relationships among Effortful Control, Affective Experiences, and Autonomic Psychophysiology

This study examined the impact of autonomic self-regulation, affective experience, and effortful control on externalizing behavior in preadolescents (n = 360) deemed at-risk for aggression. Autonomic self-regulation was assessed using measurements of respiratory sinus arrhythmia and skin conductance levels as markers for parasympathetic and sympathetic functioning. Affective experience and effortful control constructs were derived using scales from the Early Adolescent Temperament Questionnaire. Structural equation modeling indicated that sympathetic and parasympathetic functioning predicted externalizing behavior even when accounting for the influence of temperament traits. These significant associations were small in magnitude. As expected, higher parasympathetic and lower sympathetic reactivity predicted greater externalizing behavior. Effortful control and affective experience also independently predicted problem behavior when accounting for autonomic functioning and each other’s influence as evidenced by small to medium significant associations. Lower levels of these constructs predicted higher problem behavior. Implications for the prevention and treatment of externalizing behavior are discussed.

Respiratory sinus arrhythmia and heart period in infancy as correlates of later oppositional defiant and callous-unemotional behaviors

Extant literature suggests that oppositional defiant disorder (ODD) and callous-unemotional (CU) behaviors in childhood and adolescence are associated with distinct patterns of psychophysiological functioning, and that individual differences in these patterns have implications for developmental pathways to disorder. Very little is known about the associations between psychophysiological functioning in infancy and later ODD and CU behaviors. This study examined associations between basal autonomic nervous system (ANS) functioning in infancy and ODD and CU behaviors in later childhood. Using longitudinal heart period (HP) and respiratory sinus arrhythmia (RSA) data from the Durham Child Health and Development Study (N = 206), the current study tested associations within a structural equation modeling framework, between continuous measures of HP and RSA across the first 2 years of life, and later ODD and CU behaviors at first grade. Results indicate that ODD and CU behaviors in childhood are associated with lower baseline RSA, but not HP, across infancy. The implications of these findings for developmental models of ODD and CU behaviors are discussed.

Dimensions of Maternal Parenting and Infants' Autonomic Functioning Interactively Predict Early Internalizing Behavior Problems.

Developmental pathways to childhood internalizing behavior problems are complex, with both environmental and child-level factors contributing to their emergence. The authors use data from a prospective longitudinal study (n = 206) to examine the associations between dimensions of caregiving experiences in the first year of life and anxious/depressed and withdrawn behaviors in early childhood. Additionally, the authors examine the extent to which these associations were moderated by infants' autonomic functioning in the first year of life indexed using measures of respiratory sinus arrhythmia (RSA) and heart period (HP). Findings suggest that higher levels of maternal sensitivity in infancy are associated with fewer anxious/depressed and withdrawn behaviors at age 3 years. Negative intrusiveness was found to be positively associated with children's anxious/depressed behaviors but not withdrawn behaviors. Further, moderation analyses suggested that the link between negative intrusive parenting during infancy and subsequent anxious/depressed behaviors is exacerbated for infants with average or low baseline HP and that positive engaging parenting during infancy was negatively related to withdrawn behaviors for infants demonstrating average to high levels baseline HP. Interestingly, RSA was not found to moderate the associations between parenting in infancy and later internalizing behavior problems suggesting that, during infancy, overall autonomic functioning may have greater implications for the development of internalizing behaviors than do parasympathetic influences alone. Implications of these findings and future directions for research are discussed.