Autonomic nervous system functioning assessed during the Still-Face Paradigm: A meta-analysis and systematic review of methods, approach and findings

Stress responses of infants and mothers to a still-face paradigm after traumatic childbirth

INTRODUCTION

One-third of women experience childbirth as traumatic and some develop symptoms of childbirth-related posttraumatic stress symptoms (CB-PTSD symptoms). Whether CB-PTSD symptoms negatively impact on physiological and psychological stress responses in mothers and their offspring and whether they are associated with mother-infant synchrony is not clear. This study aimed to investigate stress responses of (1) mothers with CB-PTSS, (2) of their infant, and (3) the physiological mother-child-synchrony at six months postpartum.

METHOD

Psychophysiological (cortisol and vagal tone) and psychological stress responses of mothers and infant's (n=31 dyads) from the Swiss TrAumatic biRth Trial (NCT03576586) were assessed during a face-to-face still-face paradigm (FFSF-R).

RESULTS

There was a significant time effect in maternal stress responses for salivary cortisol, vagal tone, and for maternal subjective stress. As expected, mothers' subjective stress increased during the stress task and mothers vagal tone changed during the first stressful period but not during the second, whereas cortisol unexpectedly decreased over the FFSF-R. Infant negative mood increased over the experiment, but there were no physiological changes. However, a significant interaction effect for mother-infant synchrony during the second reunion period of the FFSF-R was found.

CONCLUSION

Although mothers and their infants were subjectively stressed, they showed only limited physiological stress responses.

Infant emotion regulation in the context of stress: Effects of heart rate variability and temperament

Stressful events are inherently emotional. As a result, the ability to regulate emotions is critical in responding effectively to stressors. Differential abilities in the management of stress appear very early in life, compelling a need to better understand factors that may shape the capacity for emotion regulation (ER). Variations in both biologic and behavioural characteristics are thought to influence individual differences in ER development. We sought to determine the differential contributions of temperament and heart rate variability (HRV; an indicator of autonomic nervous system function) to infant resting state emotionality and emotional reactivity in response to a stressor at 6 months of age. Participants included 108 mother-infant dyads. Mothers completed a measure of infant temperament at 6 months postnatal. Mother and infant also participated in a standardized stressor (the Repeated Still Face Paradigm) at that time. Electrocardiographic data were acquired from the infant during a baseline resting state and throughout the stressor. Fast Fourier Transformation was used to analyse the high frequency (HF) domain of HRV, a measure of parasympathetic nervous system activity. Infant ER was measured via standardized coding of emotional distress behaviours from video-records at baseline and throughout the stressor. Severity of mothers' depressive symptoms was included as a covariate in analyses. Results of linear regression indicate that neither temperament nor HRV were associated significantly with an infant's emotional resting state, although a small effect size was found for the relationship between infant negative affectivity and greater emotional distress (β = 0.23, p = 0.08) prior to the stressor. Higher HF-HRV (suggesting parasympathetic dominance) was related to greater emotional distress in response to the stressor (β = 0.34, p = 0.009). This greater emotional reactivity may reflect a more robust capacity to mount an emotional response to the stressor when infants encounter it from a bedrock of parasympathetic activation. Findings may inform eventual markers for assessment of ER in infancy and areas for intervention to enhance infant management of emotions, especially during stressful events.

Effects of prenatal opioid exposure on infant sympathetic and parasympathetic nervous system activity

Prenatal opioid exposure has been associated with developmental problems, including autonomic nervous system dysregulation. However, little is known about the effects of prenatal opioid exposure on the autonomic nervous system beyond the first days of life, particularly across both the parasympathetic and sympathetic branches, and when accounting for exposure to other substances. The present study examined the effects of prenatal exposure to opioid agonist therapy (OAT, e.g., methadone) and other opioids on infant autonomic nervous system activity at rest and in response to a social stressor (the Still-Face Paradigm) at six months among 86 infants varying in prenatal opioid and other substance exposure. Results indicated that OAT and other opioids have unique effects on the developing autonomic nervous system that may further depend on subtype (i.e., methadone versus buprenorphine) and timing in gestation. Results are discussed in the context of theoretical models of the developing stress response system.

Preliminary Technical Validation of LittleBeats™: A Multimodal Sensing Platform to Capture Cardiac Physiology, Motion, and Vocalizations

Across five studies, we present the preliminary technical validation of an infant-wearable platform, LittleBeats™, that integrates electrocardiogram (ECG), inertial measurement unit (IMU), and audio sensors. Each sensor modality is validated against data from gold-standard equipment using established algorithms and laboratory tasks. Interbeat interval (IBI) data obtained from the LittleBeats™ ECG sensor indicate acceptable mean absolute percent error rates for both adults (Study 1, N = 16) and infants (Study 2, N = 5) across low- and high-challenge sessions and expected patterns of change in respiratory sinus arrythmia (RSA). For automated activity recognition (upright vs. walk vs. glide vs. squat) using accelerometer data from the LittleBeats™ IMU (Study 3, N = 12 adults), performance was good to excellent, with smartphone (industry standard) data outperforming LittleBeats™ by less than 4 percentage points. Speech emotion recognition (Study 4, N = 8 adults) applied to LittleBeats™ versus smartphone audio data indicated a comparable performance, with no significant difference in error rates. On an automatic speech recognition task (Study 5, N = 12 adults), the best performing algorithm yielded relatively low word error rates, although LittleBeats™ (4.16%) versus smartphone (2.73%) error rates were somewhat higher. Together, these validation studies indicate that LittleBeats™ sensors yield a data quality that is largely comparable to those obtained from gold-standard devices and established protocols used in prior research.

Pregnant women's autonomic responses to an infant cry predict young infants' behavioral avoidance during the still-face paradigm

Research suggests that women's autonomic nervous system responses to infant cries capture processes that affect their parenting behaviors. The aim of this study was to build on prior work by testing whether pregnant women's autonomic responses to an unfamiliar infant crying also predict their infants' emerging regulation abilities. Participants included 97 women in their third trimester of pregnancy, located in the United States. Most participants identified as White/non-Hispanic (48%) or Hispanic (30%), their mean age was approximately 30 years, and the modal family income was $40,000-$79,999. Pregnant women's respiratory sinus arrhythmia (RSA) and skin conductance levels (SCL)-which are thought to capture emotional engagement and behavioral inhibition, respectively-were measured while the women watched a relaxing video and a video of an unfamiliar infant crying. Approximately 7 months later, women and their infants completed the still-face paradigm (SFP). Infants' avoidance and resistance behaviors during the SFP reunions were rated. Pregnant women's RSA and SCL responses to the infant cry video uniquely predicted infants' avoidance (but not resistance) during the SFP. Infants displayed higher levels of avoidance when their mothers exhibited lower levels of RSA reactivity or when their mothers exhibited higher levels of SCL activity in response to the infant cry video. Maternal sensitivity during mother-infant free-play interactions did not mediate the associations between pregnant women's autonomic responses to the cry video and infants' avoidant behavior during the SFP. Discussion focuses on potential mechanisms underlying associations between pregnant women's autonomic responses to infant distress and infants' socioemotional development. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Spontaneous infant crying modulates vagal activity in real time

Porges' polyvagal theory (1991) proposes that the activity of the vagal nerve modulates moment-by-moment changes in adaptive behavior during stress. However, most work, including research with infants, has only examined vagal changes at low temporal resolutions, averaging 30+ s across phases of structured stressor paradigms. Thus, the true timescale of vagal regulation-and the extent to which it can be observed during unprompted crying-is unknown. The current study utilized a recently validated method to calculate respiratory sinus arrhythmia (RSA) dynamically at a high resolution of 5 Hz (updated every 200 ms) in a home-based infant study. Using an event-related analysis, we calculated the relative change in RSA around the onset of naturally occurring unprompted instances of n = 41 infants' 180 crying events. As predicted, RSA significantly decreased after the onset of crying compared to non-crying chance changes in RSA. Decreasing trends in RSA were driven by infants with higher pre-cry RSA values, infants rated lower in Negative Affectivity, and those rated both high and low in Orienting by their mothers. Our results display the timescale of RSA in spontaneous and naturalistic episodes of infant crying and that these dynamic RSA patterns are aligned with real-time levels of RSA and also caregiver-reported temperament.

Vagal Flexibility Moderates the Links between Observed Sensitive Caregiving in Infancy and Externalizing Behavior Problems in Middle Childhood

This study explored how patterns of physiological stress reactivity underpin individual differences in sensitivity to early rearing experiences and childhood risk for psychopathology. To examine individual differences in parasympathetic functioning, past research has largely relied on static measures of stress reactivity (i.e., residual and change scores) in infancy which may not adequately capture the dynamic nature of regulation across contexts. Using data from a prospective longitudinal study of 206 children (56% African Americans) and their families, this study addressed these gaps by employing the latent basis growth curve model to characterize the dynamic, non-linear patterns of change in infants' respiratory sinus arrhythmia (i.e., vagal flexibility) across the Face-to-Face Still-Face Paradigm. Furthermore, it investigated whether and how infants' vagal flexibility moderates the links between sensitive parenting, observed during a free play task when children were 6 months of age, and parent-report of children's externalizing problems at 7 years of age. Results of the structural equation models revealed that infants' vagal flexibility moderates the predictive relations between sensitive parenting in infancy and children's later externalizing problems. Simple slope analyses revealed that low vagal flexibility, characterized by less suppression and flatter recovery patterns, exacerbated risk for externalizing psychopathology in the context of insensitive parenting. Children with low vagal flexibility also benefited most from sensitive parenting, as indicated by the lower number of externalizing problems. Findings are interpreted in the light of the biological sensitivity to context model and provide evidence for vagal flexibility as a biomarker of individual's sensitivity to early rearing contexts.

Parental sensitivity modifies the associations between maternal prenatal stress exposure, autonomic nervous system functioning and infant temperament in a diverse, low-income sample

Evidence suggests that adversity experienced during fetal development may shape infant physiologic functioning and temperament. Parental sensitivity is associated with child stress regulation and may act as a buffer against risk for intergenerational health effects of pre- or postnatal adversity. Building upon prior evidence in a racially and ethnically diverse sample of infants (M infant age = 6.5 months) and women of low socioeconomic status, this study examined whether coded parenting sensitivity moderated the association between an objective measure of prenatal stress exposures (Stressful Life Events (SLE)) and infant parasympathetic (respiratory sinus arrhythmia; RSA) or sympathetic (pre-ejection period; PEP) nervous system functioning assessed during administration of the Still-Face-Paradigm (SFP) (n = 66), as well as maternal report of temperament (n = 154). Results showed that parental sensitivity moderated the associations between prenatal stress exposures and infant RSA reactivity, RSA recovery, PEP recovery, and temperamental negativity. Findings indicate that greater parental sensitivity is associated with lower infant autonomic nervous system reactivity and greater recovery from challenge. Results support the hypothesis that parental sensitivity buffers infants from the risk of prenatal stress exposure associations with offspring cross-system physiologic reactivity and regulation, potentially shaping trajectories of health and development and promoting resilience.

Associations among maternal lifetime trauma, psychological symptoms in pregnancy, and infant stress reactivity and regulation

Maternal trauma has intergenerational implications, including worse birth outcomes, altered brain morphology, and poorer mental health. Research investigating intergenerational effects of maternal trauma on infant stress reactivity and regulation is limited. Maternal mental health during pregnancy may be a contributor: psychopathology is a sequela of trauma exposure and predictor of altered self-regulatory capacity in offspring of affected mothers. We assessed associations among maternal lifetime trauma and infant stress responsivity, mediated by psychological symptoms in pregnancy. Mothers reported lifetime trauma history and anxiety, depressive, and posttraumatic stress symptoms during pregnancy. At infant age 6 months, stress reactivity and regulation were assessed via maternal behavior ratings (Infant Behavior Questionnaire-Revised, IBQ-R) and behavioral (negative mood) and physiological (respiratory sinus arrhythmia, RSA) markers during a laboratory stressor (Still-Face Paradigm). Maternal trauma was directly associated with lower infant physiological regulation and indirectly associated with lower levels of both infant behavioral and physiological regulation via higher maternal anxiety during pregnancy. Maternal trauma was also indirectly associated with higher infant reactivity via higher maternal anxiety during pregnancy. Post hoc analyses indicated differential contributions of maternal prenatal versus postnatal anxiety to infant outcomes. Findings highlight potential contributory mechanisms toward maladaptive child stress response, which has been associated with poor behavioral, cognitive, and academic outcomes.

Parents' Physiological Reactivity to Child Distress and Associations with Parenting Behaviour: A Systematic Review

This systematic review and narrative synthesis characterized parents' physiological stress responses to child distress and how parents' physiological and behavioural responses relate. The review was pre-registered with PROSPERO (#CRD42021252852). In total, 3,607 unique records were identified through Medline, Embase, PsycINFO, and CINAHL. Fifty-five studies reported on parents' physiological stress responses during their young child's (0-3 years) distress and were included in the review. Results were synthesized based on the biological outcome and distress context used and risk of bias was evaluated. Most studies examined cortisol or heart rate variability (HRV). Small to moderate decreases in parents' cortisol levels from baseline to post-stressor were reported across studies. Studies of salivary alpha amylase, electrodermal activity, HRV, and other cardiac outcomes reflected weak or inconsistent physiological responses or a paucity of relevant studies. Among the studies that examined associations between parents' physiological and behavioural responses, stronger associations emerged for insensitive parenting behaviours and during dyadic frustration tasks. Risk of bias was a significant limitation across studies and recommendations for future research are discussed.

More than fear: Contributions of biobehavioral synchrony and infants' reactivity to cooperative care

We present two challenges to the fearful ape hypothesis: (1) biobehavioral synchrony precedes and moderates the effects of fear on cooperative care, and (2) cooperative care emerges in a more bidirectional manner than Grossmann acknowledges. We present evidence demonstrating how dyadic differences in co-regulation and individual differences in infants' reactivity shape caregivers' responses to infant affect.

Dynamics of mother-infant parasympathetic regulation during face-to-face interaction: The role of maternal emotion dysregulation

The dynamics of parent-infant physiology are essential for understanding how biological substrates of emotion regulation are organized during infancy. Although parent-infant physiological processes are dyadic in nature, research is limited in understanding how one person's physiological responses predict one's own and as well as the other person's responses in the subsequent moment. In this study, we examined mother-infant respiratory sinus arrhythmia (RSA) dynamics during the Still-Face Paradigm (SFP) among 106 mothers (M_age  = 29.54) and their 7-month-old infants (55 males). Given mothers' role in shaping dyadic interactions with their infant, we also tested how mothers' self-reported emotion dysregulation (measured via the Difficulties in Emotion Regulation Scale) associated with these dynamics. Results showed that both mothers' and infants' RSA tended to return to their respective homeostatic points (i.e., exhibited return strength) during each SFP episode, indicating stability in RSA for mother-infant dyads. Significant shifts in mother and infant RSA return strength were observed across SFP episodes, highlighting the role of contextual demands on each individual's physiological dynamics. Mother-infant RSA dynamics varied as a function of maternal self-reported emotion dysregulation. Specifically, RSA levels of infants with more dysregulated mothers had a weaker tendency to return to homeostasis during the Reunion episode and were less affected by their mothers' RSA during the Still-Face and Reunion episodes of the SFP, suggesting a less effective coregulatory influence. Our findings have implications for the intergenerational transmission of emotion dysregulation via mother-infant physiological dynamics.

Coupling between prefrontal brain activity and respiratory sinus arrhythmia in infants and adults

Self-regulation is an essential aspect of healthy child development. Even though infants depend on their caregivers for co-regulation during the first years, they begin to gain regulatory abilities through social interactions as well as their own developing agency and inhibitory control. These early regulatory abilities continue to increase with the development of both the prefrontal cortex and the vagal system. Importantly, theoretical accounts have suggested that the prefrontal cortex and the vagal system are linked through forward and backward feedback loops via the limbic system. Decreased coupling within this link is suggested to be associated with psychopathology. The primary goal of this study was to examine whether intrapersonal coupling of prefrontal brain activity and respiratory sinus arrhythmia is evident in infancy. Using the simultaneous assessment of functional near-infrared spectroscopy and electrocardiography, we used Cross-Recurrence Quantification Analysis to assess the coupling of prefrontal brain activity and respiratory sinus arrhythmia in 69 4- to 6-month-old infants and their mothers during a passive viewing condition. However, we did not find significant coupling between the PFC and RSA in infants and adult caregivers. Future studies could examine social contexts associated with greater emotional reactivity to deepen our understanding of the pathways involved in self-regulation.

Bringing the laboratory into the home: A protocol for remote biobehavioral data collection in pregnant women with emotion dysregulation and their infants

Pregnant women struggling with emotion dysregulation may be more likely to engage in a wide range of health risk behaviors. This protocol describes a study on intergenerational transmission of emotion dysregulation from the third trimester of pregnancy to 18 months postpartum. Biobehavioral markers of emotion dysregulation are typically measured in laboratory settings which was prohibited by many universities during the COVID-19 pandemic. We describe how markers of emotion dysregulation (e.g. maternal, fetal, and infant heart rate variability) are collected remotely. We detail how data collection can be augmented to reach diverse populations who may not otherwise participate in laboratory-based research.

Unique Contributions of Maternal Prenatal and Postnatal Emotion Dysregulation on Infant Respiratory Sinus Arrhythmia

Prenatal intrauterine exposures and postnatal caregiving environments may both shape the development of infant parasympathetic nervous system (PNS) activity. However, the relative contributions of prenatal and postnatal influences on infant respiratory sinus arrhythmia (RSA)-an index of PNS functioning-are relatively unknown. We examined whether prenatal and postnatal maternal emotion dysregulation, a transdiagnostic construct that spans mental health diagnoses, were independently related to infant RSA trajectories during a social stressor, the still-face paradigm. Our sample included 104 mothers and their 7-month-old infants. Maternal emotion dysregulation was measured with the Difficulties in Emotion Regulation Scale during the 3rd trimester of pregnancy and again at a 7-month postpartum laboratory visit. Infant RSA was recorded during the still-face paradigm. Only postnatal maternal emotion dysregulation was associated with infant RSA. Specifically, high postnatal emotion dysregulation was associated with a blunted (i.e., dampened reactivity and recovery) infant RSA response profile. Infant sex did not moderate the associations between maternal emotion dysregulation and infant RSA. Findings suggest that postnatal interventions to promote effective maternal emotion regulation may reduce risk for infants' dysregulated psychophysiological stress responses.

Breastfeeding duration and vagal regulation of infants and mothers

BACKGROUND

Vagal regulation within the parasympathetic nervous system supports self-regulation and social engagement. Research has suggested that early feeding practices may influence mother-infant vagal functioning.

AIM

We aimed to examine the association between breastfeeding duration and mother-infant vagal regulation during an interaction. We hypothesized that breastfeeding duration would be positively associated with adaptive vagal regulation in infants and mothers.

METHOD

204 mother-infant dyads (infant mean age 6 months) completed the face-to-face still-face (FFSF) task. During the task, vagal regulation indexed by respiratory sinus arrhythmia (RSA, a component of heart rate variability) was calculated through continuously recorded electrocardiogram signals. Breastfeeding duration and demographic information were reported by mothers. Linear mixed models were adopted to estimate the associations between breastfeeding duration and repeated measures of RSA in infants and mothers throughout the FFSF.

RESULTS

Infants breastfed for a longer duration demonstrated lower RSA throughout the FFSF (B = -0.06, 95 % CI: -0.09 to -0.03), suggesting active physiological mobilization to engage in interaction and regulate distress. Mothers with longer breastfeeding duration displayed higher baseline RSA and higher overall RSA levels (higher vagal control) during the FFSF (B = 0.06, 95 % CI: 0.02 to 0.09), indicating a calmer and regulated state.

CONCLUSION

Longer breastfeeding duration was associated with more adaptive mother-infant vagal regulation during the interaction, indicating a positive dose-response association. This finding reveals breastfeeding practice as a factor contributing to infant effective vagal regulation and further supports WHO recommendation on exclusive breastfeeding for the first 6 months and continuing breastfeeding to 24 months and beyond.

The Effects of a Prenatal Mindfulness Intervention on Infant Autonomic and Behavioral Reactivity and Regulation

OBJECTIVE

Maternal health and wellness during pregnancy are associated with long-term health outcomes in children. The current study examined whether infants of women who participated in a mindfulness-based intervention during pregnancy that reduced levels of stress and depression, increased physical activity, and improved glucose tolerance differed on biobehavioral markers of psychopathological and physical health risk compared with infants of women who did not.

METHODS

Participants were 135 mother-infant dyads drawn from a racially and ethnically diverse, low-income sample experiencing high stress. The women participated in an intervention trial during pregnancy that involved assignment to either mindfulness-based intervention or treatment-as-usual (TAU). Infants of women from both groups were assessed at 6 months of age on sympathetic (preejection period), parasympathetic (respiratory sinus arrhythmia), and observed behavioral (negativity and object engagement) reactivity and regulation during the still face paradigm. Linear mixed-effects and generalized linear mixed-effects models were used to examine treatment group differences in infant outcomes.

RESULTS

Relative to those in the intervention group, infants in the TAU group showed a delay in sympathetic activation and subsequent recovery across the still face paradigm. In addition, infants in the intervention group engaged in higher proportions of self-regulatory behavior during the paradigm, compared with the TAU group. No significant effect of intervention was found for parasympathetic response or for behavioral negativity during the still face paradigm.

CONCLUSIONS

Findings provide evidence that maternal participation in a short-term, group mindfulness-based intervention during pregnancy is associated with the early development of salutary profiles of biobehavioral reactivity and regulation in their infants. Because these systems are relevant for psychopathology and physical health, prenatal behavioral interventions may benefit two generations.

Developmental foundations of physiological dynamics among mother-infant dyads: The role of newborn neurobehavior

This study tested whether newborn attention and arousal provide a foundation for the dynamics of respiratory sinus arrhythmia (RSA) in mother-infant dyads. Participants were 106 mothers (M_age  = 29.54) and their 7-month-old infants (55 males and 58 White and non-Hispanic). Newborn attention and arousal were measured shortly after birth using the NICU Network Neurobehavioral Scale. Higher newborn arousal predicted a slower return of infant RSA to baseline. Additionally, greater newborn attention predicted mothers' slower return to baseline RSA following the still-face paradigm, and this effect only held for mothers whose infants had lower newborn arousal. These findings suggest that newborn neurobehavior, measured within days of birth, may contribute to later mother-infant physiological processes while recovering from stress.

Adapting psychophysiological data collection for COVID-19: The "Virtual Assessment" model

The COVID-19 pandemic has significantly disrupted research activities globally. Researchers need safe and creative procedures to resume data collection, particularly for projects evaluating infant mental health interventions. Remote research is uniquely challenging for psychophysiological data collection, which typically requires close contact between researchers and participants as well as technical equipment frequently located in laboratory settings. In accordance with public health guidance, we adapted procedures and developed novel protocols for a "virtual assessment" in which women and infants provided behavioral and psychophysiological data from their own homes while researchers coordinated remotely. Data collected at virtual visits included video-recorded parent-child interactions and autonomic nervous system data. Adaptations were designed to optimize safety and data quality while minimizing participant burden. In the current paper, we describe these adaptations and present data evaluating their success across two sites in the United States (University of Delaware and University of Utah), focusing specifically on autonomic nervous system data collected during the well-validated Still-Face Paradigm (SFP). We also discuss advantages and challenges of translating traditional lab procedures into the virtual assessment model. Ultimately, we hope that disseminating these procedures will help other researchers resume safe data collection related to infant mental health during the COVID-19 pandemic and beyond.

Sympathetic nervous system functioning during the face-to-face still-face paradigm in the first year of life

Contemporary theories of early development and emerging child psychopathology all posit a major, if not central role for physiological responsiveness. To understand infants' potential risk for emergent psychopathology, consideration is needed to both autonomic reactivity and environmental contexts (e.g., parent-child interactions). The current study maps infants' arousal during the face-to-face still-face paradigm using skin conductance (n = 255 ethnically-diverse mother-infant dyads; 52.5% girls, mean infant age = 7.4 months; SD = 0.9 months). A novel statistical approach was designed to model the potential build-up of nonlinear counter electromotive force over the course of the task. Results showed a significant increase in infants' skin conductance between the Baseline Free-play and the Still-Face phase, and a significant decrease in skin conductance during the Reunion Play when compared to the Still-Face phase. Skin conductance during the Reunion Play phase remained significantly higher than during the Baseline Play phase; indicating that infants had not fully recovered from the mild social stressor. These results further our understanding of infant arousal during dyadic interactions, and the role of caregivers in the development of emotion regulation during infancy.

Acute Maternal Stress Disrupts Infant Regulation of the Autonomic Nervous System and Behavior: A CASP Study

Exposure to maternal stress is assumed to influence infant health and development across the lifespan. The autonomic nervous system (ANS) is especially sensitive to the effects of the early caregiving environment and linked to predictors of later mental health. Understanding how exposure to maternal stress adversely affects the developing ANS could inform prevention. However, there is no agreed upon definition of maternal stress making its study difficult. Here we use the Caretaker Acute Stress Paradigm (CASP) to study the effects of maternal stress in an experimentally controlled laboratory setting. The CASP has 5 episodes, a natural play, followed by a caretaker stressor (or control) condition, another play, a classic still face episode, followed by another play. A total of 104 4-months-old infants and their mothers were randomly assigned to either the caretaker-stress or caretaker-control condition. Changes in behavior, heart rate (HR), and respiratory sinus arrhythmia (RSA) before and after the introduction of the stressor (or control condition) were recorded and compared. Infants in the maternal stress condition showed significantly more behavioral distress [X 2 = (1, N = 104) = 4.662, p = 0.031]. Moreover, infants whose mothers were in the stress condition showed an significant increase in heart rate after the caretaker condition [F (1, 102) = 9.81, p = 0.002]. Finally we observed a trend to faster RSA recovery in infants of the control condition [F (1, 75) = 3.539, p = 0.064]. Results indicate that exposure to acute maternal stress affects infant regulation of the autonomic nervous system and behavior.

Caregiver and Young Child Biological Attunement In Distress Contexts: A Systematic Review and Narrative Synthesis

The objective of the current study was to systematically review the literature on caregiver-child biological attunement within distress contexts during the first three years of life. A total of 9932 unique abstracts were identified through Medline, Embase, PsycINFO, CINAHL, and Scopus databases. Thirty-six studies provided data from caregivers and their infants or toddlers within a distress paradigm, used biological indicators of distress, and assessed the relations between caregiver and child biological indicators. Findings were synthesized based on biological indicators, type of analysis, and measurement epochs pre- and post-distress. Most articles examined cortisol. Associations between caregiver and child cortisol indicators were moderate to large, though findings varied depending on the analysis used and measurement epochs examined. Many of the findings examining relations between mother and child cardiac, sAA, and EEG indicators were weak or inconsistent, likely due to the limitations of methodological approaches used to capture the complexity of the caregiver-child attunement process. Gaps in the literature and suggestions for future research are discussed.

Infant physiological activity and the early emergence of social communication

Early in life, social engagement is facilitated by effective regulation during times of rest and stress. Physiological regulation during social play and in response to sudden environmental changes or social stressors may play an important role in sustaining social engagement in infancy and facilitate the acquisition of early social-communication skills. The aim of this study was to investigate the role of physiological activity during social play, including respiratory sinus arrhythsmia (RSA) and heart rate-defined attention, in the early emergence of social-communication skills. Using RSA as an index of vagal tone, we measured vagal tone, vagal suppression, and heart rate-defined sustained attention during a social interaction with a caregiver (i.e., the Still-Face procedure) in 21 infants aged 3-4 months. At 9 months, caregivers reported on their infant's early social-communication skills. Results suggest that RSA, RSA suppression, and heart rate-defined sustained attention to a caregiver are significantly associated with early-emerging social-communication skills at 9 months. In addition, RSA and heart rate-defined sustained attention during social play were highly related. Suppression of RSA during the Still-Face phase of the infant-caregiver interaction emerged as a particularly strong predictor of later-developing social-communication skills, including 9-month-olds' ability to use eye gaze, facial expression, and gestures to communicate.

Associations between acoustic features of maternal speech and infants' emotion regulation following a social stressor

Caregiver voices may provide cues to mobilize or calm infants. This study examined whether maternal prosody predicted changes in infants' biobehavioral state after the still face, a stressor in which the mother withdraws and reinstates social engagement. Ninety-four dyads participated in the study (infant age 4-8 months). Infants' heart rate and respiratory sinus arrhythmia (measuring cardiac vagal tone) were derived from an electrocardiogram (ECG). Infants' behavioral distress was measured by negative vocalizations, facial expressions, and gaze aversion. Mothers' vocalizations were measured via a composite of spectral analysis and spectro-temporal modulation using a two-dimensional fast Fourier transformation of the audio spectrogram. High values on the maternal prosody composite were associated with decreases in infants' heart rate (β = -.26, 95% CI: [-0.46, -0.05]) and behavioral distress (β = -.23, 95% CI: [-0.42, -0.03]), and increases in cardiac vagal tone in infants whose vagal tone was low during the stressor (1 SD below mean β = .39, 95% CI: [0.06, 0.73]). High infant heart rate predicted increases in the maternal prosody composite (β = .18, 95% CI: [0.03, 0.33]). These results suggest specific vocal acoustic features of speech that are relevant for regulating infants' biobehavioral state and demonstrate mother-infant bi-directional dynamics.

Affect and gaze responses during an Emotion-Evoking Task in infants at an increased likelihood for autism spectrum disorder

Background

The majority of research examining emotional difficulties in autism spectrum disorder (ASD) prior to age 2 relies on parent report.

Methods

We examined behavioral responses (affect and gaze) during emotionally salient tasks designed to elicit mildly positive and negative emotional states in infants. At 12 and 18 months, infants at an increased likelihood for an ASD diagnosis (IL; have an older sibling with ASD; n = 60) and low likelihood (LL; no family history of ASD; n = 21) completed the Emotion-Evoking (EE) Task and parents completed the Infant Behavior Questionnaire-Revised (IBQ-R). All children received an Autism Diagnostic Observation Scale—second Edition assessment for ASD symptomatology at 24 months.

Results

The main findings were (1) the IL group displayed higher rates of negative affect and spent less time looking at the task objects compared to the LL group, and (2) affect and gaze scores at 12 and 18 months, but not scores on the IBQ-R, predicted ASD symptoms at 24 months.

Limitations

The data were drawn from an IL sample and may not be generalizable to the general ASD population, and the children were not followed to determine a diagnosis of ASD.

Conclusion

These results suggest that behavioral responses can provide important information that complements parent reports of emotional regulation in IL infants as early as 12 months of age.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13229-021-00468-0.

Infant weight-for-length gain associated with autonomic nervous system reactivity

BACKGROUND

Research suggests that children's health and well-being are supported by core adaptive systems, including the autonomic nervous system (ANS). Despite evidence for the importance of adulthood ANS regulation in the development of disease, few studies have examined how early development may influence emerging ANS function. Therefore, we examined how infant adiposity gain during early infancy related to ANS regulation at 6 months.

METHODS

Infant weight and length were abstracted from birth records and measured during the 6-month assessment in a low-income, racially/ethnically diverse sample (N = 60). WHO-standardized weight-for-length-gain change was calculated across the first 6 months of life. ANS reactivity was measured as the combined sympathetic (i.e., pre-ejection period) and parasympathetic (i.e., respiratory sinus arrhythmia) nervous system responses during the developmentally challenging Still Face Paradigm (SFP). ANS "classic reactivity" response was characterized by paired sympathetic activation and parasympathetic withdrawal.

RESULTS

Lower weight-for-length gain in the first 6 months predicted classic reactivity during still face. However, greater weight-for-length gain predicted "classic reactivity" during the reunion, when infants were expected to recover, suggesting autonomic dysregulation.

CONCLUSIONS

These findings suggest an association between early life adiposity gain and the development of infant ANS regulation.

IMPACT

Adiposity gain during early infancy was associated with autonomic nervous system regulation at 6 months. This study identifies early adiposity gain (greater than average infant weight-for-length gain) as a risk for ANS dysregulation. This research focuses on a critical developmental period of ANS plasticity. If confirmed, findings can be used to inform early intervention programs targeting obesity prevention and to promote self-regulation.

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.

A method for measuring dynamic respiratory sinus arrhythmia (RSA) in infants and mothers

The measurement of respiratory sinus arrythmia (RSA) in infants, children and adults is critical to the study of physiological regulation, and more recently, interpersonal physiological covariation, but it has been impeded by methods that limit its resolution to 30 s or longer. Recent analytical developments have suggested methods for studying dynamic RSA in adults, and we have extended this work to the study of infants and mothers. In the current paper, we describe a new analytical strategy for estimating RSA time series for infants and adults. Our new method provides a means for studying physiological synchrony in infant-mother dyads that offers some important advantages relative to existing methods that use inter-beat-intervals (e.g. Feldman, Magori-Cohen, Galili, Singer, & Louzoun, 2011). In the middle sections of this paper, we offer a brief tutorial on calculating RSA continuously with a sliding window and review the empirical evidence for determining the optimal window size. In order to confirm the reliability of our results, we briefly discuss testing synchrony by randomly shuffling the dyads to control for spurious correlations, and also by using a bootstrapping technique for calculating confidence intervals in the cross-correlation function. One important implication that emerges from applying this method is that it is possible to measure both positive and negative physiological synchrony and that these categorical measures are differentially predictive of future outcomes.

Physiological measurement of emotion from infancy to preschool: A systematic review and meta-analysis

INTRODUCTION

Emotion regulation, the ability to regulate emotional responses to environmental stimuli, develops in the first years of life and plays an important role in the development of personality, social competence, and behavior. Substantial literature suggests a relationship between emotion regulation and cardiac physiology; specifically, heart rate changes in response to positive or negative emotion-eliciting stimuli.

METHOD

This systematic review and meta-analysis provide an in-depth examination of research that has measured physiological responding during emotional-evoking tasks in children from birth to 4 years of age.

RESULTS

The review had three main findings. First, meta-regressions resulted in an age-related decrease in baseline and task-related heart rate (HR) and increases in baseline and task-related respiratory sinus arrhythmia (RSA). Second, meta-analyses suggest task-related increases in HR and decreases in RSA and heart rate variability (HRV), regardless of emotional valence of the task. Third, associations between physiological responding and observed behavioral regulation are not consistently present in children aged 4 and younger. The review also provides a summary of the various methodology used to measure physiological reactions to emotional-evoking tasks, including number of sensors used and placement, various baseline and emotional-evoking tasks used, methods for extracting RSA, as well as percentage of loss and reasons for loss for each study.

CONCLUSION

Characterizing the physiological reactivity of typically developing children is important to understanding the role emotional regulation plays in typical and atypical development.

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

OBJECTIVE

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.

METHODS

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).

RESULTS

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.

DISCUSSION

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.

The psychobiological consequences of child separation at the border: lessons from research on attachment and emotion regulation

In the spring of 2018, the Attorney General of the United States issued a memorandum declaring a "zero tolerance policy" under which all adults entering the United States illegally would be criminally prosecuted, and, if traveling with minor children, forcibly separated from their children. Although the government was ordered to reunite the children with their parents it is still unclear how many children have been or remain separated. Given the high risk of permanent harm to a vulnerable population, and the fact that this risk may continue into the near future, we present a review of what nearly eight decades of scholarly research has taught us about the damaging impact of deprivation and separation from parents. The article briefly reviews the origins of attachment theory as well as empirical studies that examine the psychobiological impact on children who experienced parental deprivation or separation. The paper concludes with recommendations, for future research.