The Development of Regulatory Functions From Birth to 5 Years: Insights From Premature Infants

This study examined physiological, emotional, and attentional regulatory functions as predictors of self-regulation in 125 infants followed 7 times from birth to 5 years. Physiological regulation was assessed by neonatal vagal tone and sleep–wake cyclicity; emotion regulation by response to stress at 3, 6, and 12 months; and attention regulation by focused attention and delayed response in the 2nd year. Executive functions, behavior adaptation, and self-restraint were measured at 5 years. Regulatory functions showed stability across time, measures, and levels. Structural modeling demonstrated both mediated paths from physiological to self-regulation through emotional and attentional processes and direct continuity between vagal tone and each level of regulation. Results support the coherence of the regulation construct and are consistent with neurobiological models on self and consciousness.     

The relation between neonatal heart period patterns and developmental outcome

Developmental psychophysiologists have long been interested in a means for evaluating infants at risk for cognitive disabilities. The current research addressed the utility of a noninvasive measure of cardiac vagal tone in predicting developmental outcome. At 40 weeks conceptional age, 3 min of resting EKG were recorded from 80 infants. Four groups of infants were evaluated: prematures who had no medical complications in the postnatal period; prematures who experienced respiratory distress syndrome during the postnatal period; term infants who experienced birth asphyxia during labor and/or postdelivery; and healthy term infants. The mental scale of the Bayley Scales of Mental Development was administered at 8 and 12 months conceptional age. Heart period data were analyzed to derive mean heart period, heart period variability, and estimates of vagal tone for each subject. Analyses of the relationship between the heart period variables and 8- and 12-month outcome (i.e., Bayley Scales) indicated that infants with high vagal tone at 40 weeks conceptional age always had positive developmental outcome at both eight and 12 months of age. Infants with low vagal tone had varied outcomes. Measures of medical complications and other measures of heart period variability were not related to developmental outcome. The results suggest that measurement of cardiac vagal tone may provide an important means for assessing risk in birth stressed populations.     

Neonatal Stress Reactivity: Predictions to Later Emotional Temperament

To investigate the relations among popular measures of neonatal stress and their link to subsequent temperament, 50 full-term newborns from a normal care nursery were examined responding to a heelstick blood draw. Baseline and heelstick measures of behavioral state, heart period, vagal tone, and salivary cortisol were obtained. Recovery measures of behavioral and cardiac activity were also analyzed. Mothers completed Rothbart's Infant Behavior Questionnaire when their infants reached 6 months of age. Baseline vagal tone predicted cortisol in response to the heelstick, suggesting that baseline vagal tone reflects the infants' ability to react to stressors. Greater reactivity to the heelstick (more crying, shorter heart periods, lower vagal tone, and higher cortisol) was associated with lower scores on "Distress-to-Limitations" temperament at 6 months. This finding was consistent with the expectation that the capacity to react strongly to an aversive stimulus would reflect better neurobehavioral organization in the newborn. Recovery measures of cardiac activity approximated and were correlated with baseline measures indicating the strong self-righting properties of the healthy newborn. Finally, vagal tone and salivary cortisol measures were not significantly related, suggesting the importance of assessing both systems in studies of the ontogeny of stress-temperament relations.     

Newborn pain cries and vagal tone: parallel changes in response to circumcision

Clinical studies have demonstrated that the cries of chronically stressed, medically compromised infants are characteristically higher and more variable in pitch than those of healthy infants. Other studies have indicated that the vagal tone of chronically stressed infants is significantly reduced in comparison to that of normal infants. A neural model of cry production has been proposed which suggests that decreased vagal tone among infants at risk may, in fact, be related to these increases in cry pitch. Using routine, unanesthetized circumcision as a model of stress, we were able to examine the relation between cry acoustics and vagal tone in normal, healthy newborns undergoing an acutely stressful event. Vocalizations, heart, and respiratory waveforms were continuously recorded from 49 (32 experimental; 17 control) 1-2-day-old, full-term infants during preoperative, surgical, and postoperative periods. Vagal tone, as measured by the amplitude of respiratory sinus arrhythmia extracted from heart period data, was significantly reduced during the severe stress of circumcision, and these reductions were paralleled by significant increases in the pitch of the infants' cries. In addition, individual differences in vagal tone measured prior to circumcision surgery were predictive of physiological and acoustic reactivity to subsequent stress. These results emphasize the potential role of vagal control of the autonomic nervous system during stress.     

Exposure to Interparental Conflict and Children''s Adjustment and Physical Health: The Moderating Role of Vagal Tone

Physiological regulation, as indexed by baseline vagal tone and delta vagal tone (the change in vagal tone during an attention-demanding or challenging task), was examined as a moderator in the relations between exposure to verbal and physical parental marital conflict and children's adjustment and physical health. Higher vagal tone was posited to serve a protective function (i.e., buffer) for children exposed to higher levels of marital conflict. Seventy-five 8- to 12-year-olds and their mothers completed measures of parental conflict, and children's adjustment and physical health. Children's vagal tone was assessed during baseline conditions and during exposure to an audiotaped interadult argument. Results indicate that higher vagal tone buffered children against increased externalizing, internalizing, and health problems related to exposure to more frequent marital conflict, especially verbal conflict. Further, higher levels of delta vagal tone protected boys against externalizing problems associated with verbal conflict, and health problems associated with physical conflict.     

Toward a developmental model of child compliance: the role of emotion regulation in infancy

The present study examined the relation between early emotion regulation and later compliance. When infants were 5, 10, and 18 months of age, they participated in a frustration task. The degree to which they reacted negatively to the stimuli and the behaviors they used to regulate that response were coded. Baseline heart rate also was recorded and a measure of cardiac vagal tone (VNA) was derived. Several tasks (electrode placement, toy clean-up, and test situation) were administered to elicit compliance/noncompliance when the participants were 30 months of age. Results revealed that infants who demonstrated low levels of regulatory behavior were more likely to be noncompliant as toddlers. Several interaction effects suggested that the prediction to later noncompliance was also dependent upon the infants' level of reactivity. Cardiac vagal tone also was related to compliance but in a contradictory fashion. High VNA was related to noncompliance to toy clean-up, whereas low VNA was related to noncompliance to electrode placement. The data provide support for a developmental model of compliance that includes the ability to regulate emotional arousal.     

Mother–Infant Vagal Regulation in the Face-To-Face Still-Face Paradigm Is Moderated by Maternal Sensitivity

Parents' physiological regulation may support infants' regulation. Mothers ( N = 152) and 6-month-old male and female infants were observed in normal and disrupted social interaction. Affect was coded at 1-s intervals and vagal tone measured as respiratory sinus arrhythmia (RSA). Maternal sensitivity was assessed in free play. Mothers and infants showed opposite patterns of RSA change. During disrupted interaction, mothers' RSA increased and infants' decreased, suggesting self-regulation of distress. During reunion, although the typical pattern was for infants to return to baseline levels, infants of sensitive mothers and sensitive mothers both showed a significant decrease in RSA from baseline. Mothers' and infants' physiological responses may be a function of mutual responsiveness.     

Classroom Climate,Cardiac Vagal Tone,and Inhibitory Control: Links to Focused Attention in First Graders

The present study aimed to investigate the role of classroom climate and self‐regulation in terms of cardiac vagal tone and inhibitory control in primary school students' focused attention. A combination of direct and indirect measures was used to assess classroom climate, sustained and selective attention, and inattention behaviors among 62 first graders. We also registered students' cardiac vagal tone at rest and their levels of inhibitory control in a reaction time task. A single underlying factor combining sustained and selective attention as well as (the lack of) inattention behaviors accounted for students' focused attention. A regression analysis revealed that classroom climate, cardiac vagal tone, and inhibitory control interacted to explain first graders' focused attention. In classrooms with a negative climate, high levels of inhibitory control attenuated the negative effect of low cardiac vagal tone on students' ability to remain focused during classroom activities. Implications for theory and practice are discussed.     

Gene-environment contributions to the development of infant vagal reactivity: the interaction of dopamine and maternal sensitivity

This study investigated dopamine receptor genes (DRD2 and DRD4) and maternal sensitivity as predictors of infant respiratory sinus arrhythmia (RSA) and RSA reactivity, purported indices of vagal tone and vagal regulation, in a challenge task at 3, 6, and 12 months in 173 infant-mother dyads. Hierarchical linear modeling (HLM) revealed that at 3 and 6 months, RSA withdrawal in response to maternal separation was greater (suggesting expected physiological regulation) in infants without the DRD2 risk allele than those with the risk allele. At 12 months, infants with the risk allele who were also exposed to maternal sensitivity showed levels of RSA withdrawal comparable to infants who were not at genetic risk. Findings demonstrate the importance of developmental analysis of gene-environment interaction.     

Vagal Suppression Buffers Against the Negative Effects of Psychological Inflexibility on Parenting Behaviors in Combat Deployed Fathers

SYNOPSIS

Objective : Vagal suppression is a parasympathetic physiological indicator of emotion regulation and social engagement behaviors, often measured via heart rate variability. Experiential avoidance reflects psychological inflexibility or poor emotion regulation. We tested the interaction effects of parental vagal suppression and experiential avoidance on observed parenting behaviors among combat deployed fathers. Design . We analyzed data from 92 male National Guard/Reserve members who had returned from a deployment to Iraq and/or Afghanistan since 2001. They were mostly European American, in their 30s, middle-class, and married. All fathers participated in home-based assessments with their spouses (if married) and a target child aged 4–13 years. Fathers’ vagal suppression was measured as the decrease in cardiac vagal tone (i.e., high frequency heart rate variability) from a neutral reading task to a father-child conflict resolution task. Experiential avoidance was self-reported. Parenting behaviors were observed during family interaction tasks and coded into positive engagement and withdrawal avoidance using a macro-level coding system. Results . Multiple regression analysis showed no main effects of vagal suppression on observed parenting, but interaction effects of experiential avoidance by vagal suppression on observed parenting. Specifically, among fathers with higher vagal suppression, we found no relations between experiential avoidance and observed parenting; among fathers with lower vagal suppression, we found an inverse association between experiential avoidance and positive engagement as well as a positive association between experiential avoidance and withdrawal avoidance. Conclusions . The effect of psychological inflexibility on military fathers’ parenting behaviors was moderated by vagal suppression. The findings have implications for the linkage between emotion regulation and parenting in military fathers.     

Cardiac vagal regulation and early peer status

A sample of 341 5 (1/2) -year-old children participating in an ongoing longitudinal study was the focus of a study on the relation between cardiac vagal regulation and peer status. To assess cardiac vagal regulation, resting measures of respiratory sinus arrhythmia (RSA) and RSA change (suppression) to 3 cognitively and emotionally challenging tasks were derived. Results indicated that vagal regulation was positively associated with peer status. In addition, mediational analyses revealed that the relation between vagal regulation and peer status was mediated through better social skills for girls and better social skills and fewer behavior problems for boys. These findings are discussed in terms of the role of vagal regulation in the facilitation of children's positive social behavior.     

Infant habituation: assessments of individual differences and short-term reliability at five months

This study is concerned with individual differences and short-term reliability of infant-control habituation of visual attention. Habituation to single female faces and to single geometric patterns was observed separately in 2 groups of comparable 5-month-olds. Each group participated in habituation twice, and habituation sessions for each were separated from one another by 10 days. Across the 2 conditions, habituation was found to be distributed into 3 patterns: Most infants decreased looking and achieved criterion in a negatively exponential fashion, some infants first increased looking and then rapidly habituated, and some infants showed fluctuating and idiosyncratic looking-time functions prior to habituating. Both qualitative patterns and quantitative indexes of habituation showed moderate but significant reliability between assessment sessions. Quantitative and psychometric characteristics of habituation and the meaningfulness of habituation of attention as an index of infant cognition are discussed.     

Back to Basics: A Bilingual Advantage in Infant Visual Habituation

Comparisons of cognitive processing in monolinguals and bilinguals have revealed a bilingual advantage in inhibitory control. Recent studies have demonstrated advantages associated with exposure to two languages in infancy. However, the domain specificity and scope of the infant bilingual advantage in infancy remains unclear. In the present study, 114 monolingual and bilingual infants were compared in a very basic task of information processing—visual habituation—at 6 months of age. Bilingual infants demonstrated greater efficiency in stimulus encoding as well as in improved recognition memory for familiar stimuli as compared to monolinguals. Findings reveal a generalized cognitive advantage in bilingual infants that is broad in scope, early to emerge, and not specific to language.     

The Relations among Infant Temperament, Security of Attachment, and Behavioral Inhibition at Twenty-Four Months

The purpose of this study was to examine the relations among infant temperament, attachment, and behavioral inhibition. 52 infants were seen at 2 days, 5, 14, and 24 months of age. Assessments were made of temperament at 2 days and 5 months of age, and attachment and behavioral inhibition were assessed at 14 and 24 months, respectively. EKG was recorded at each assessment, and measures of heart period and vagal tone were computed. Distress to pacifier withdrawal at 2 days of age was related to insecure attachment at 14 months. 2 types of distress reactivity at 5 months, reactivity to frustration and reactivity to novelty, were identified and related to high vagal tone. Attachment classification at 14 months was directly related to inhibited behavior at 24 months. Infants classified as insecure/resistant were more inhibited than those classified as insecure/avoidant. In addition, an interaction of infant reactivity to frustration and attachment classification was found to predict inhibition at 24 months. Infants classified as insecure/resistant and who had not cried to the arm restraint procedure at 5 months were the most inhibited at 24 months. These findings are discussed in terms of hypotheses regarding multiple modes of distress reactivity and regulation in early infancy and their different social and behavioral outcomes.     

Parental socialization, vagal regulation, and preschoolers' anxious difficulties: direct mothers and moderated fathers

Parental supportiveness and protective overcontrol and preschoolers' parasympathetic regulation were examined as predictors of temperamental inhibition, social wariness, and internalizing problems. Lower baseline vagal tone and weaker vagal suppression were expected to mark poorer dispositional self-regulatory capacity, leaving children more susceptible to the influence of parental socialization. Less supportive mothers had preschoolers with more internalizing problems. One interaction between baseline vagal tone and maternal protective overcontrol, predicting social wariness, conformed to the moderation hypothesis. Conversely, vagal suppression moderated several links between paternal socialization and children's anxious difficulties in the expected pattern. There were more links between mothers' self-reported parenting and child outcomes than were noted for direct observations of maternal behavior, whereas the opposite tended to be true for fathers.     

Individual differences in habituation rates and object concept performance.

The scores from object concept tasks for 15 infants at 14 months of age were analyzed with respect to their habituation rates at 4 months of age. Partitioning of the data according to subjects categorized as fast and slow habituators brought some organization consistent with the notion that the former are more advanced than the latter. Statistical differences between groups did not obtain, but a significant correlation between ranked task scores and habituation ratios offers some support to the interpretation. The possibility of using habituation rates or ratios as an index of differences in processing, perhaps with some predictive value, may be considered if further evidence of relations to later cognitive performanceis found.     

CS modality effects in one-trial backward and forward excitatory conditioning as assessed by conditioned suppression of licking in rats

Rats received a single 4-sec 1-mA grid-shock US either preceded or followed by a 4-sec tone or light CS. Conditioning was later assessed by comparing the amount of lick suppression evoked by the forward- or backward-paired CS versus an explicitly unpaired CS. The backward-paired CS produced more suppression than the unpaired CS only when both were tone; the light evoked strong suppression whether paired or not. In the forward procedure, tone produced more suppression when paired and less when unpaired than did light; conditioning thus appeared stronger with the tone. In one experiment, observations showed that rats froze during the forward-paired tone but not during the light. Increasing CS duration from 4 to 12 sec had no effect for the forward-paired light but increased freezing to the forward-paired tone. Another experiment showed similar unconditioned suppression to tone and light but faster habituation to tone. Problems that these results create for interpreting evidence for excitatory backward conditioning in the conditioned suppression procedure are discussed.     

Behavioral and physiological responsivity, sleep, and patterns of daily cortisol production in infants with and without colic

To describe the behavioral and physiological responses associated with colic, the responses of 20 two-month-old infants with and 20 without colic were studied during a physical examination. Parents kept a diary of infant behaviors (including crying and fussing) for 3 days following the visit. Using Wessel, Cobb, Jackson, Harris, & Detwiler criteria, colic was defined as fussing/crying for 3 hr or more on each of the 3 days. Behavioral data coded by "blind" observers showed that during the physical exam, colic infants cried twice as much, cried more intensely, and were more inconsolable than were control infants. Despite these behavioral differences, heart rate, vagal tone, and cortisol measures indicated no appreciable difference in physiological responsivity for the two groups. At home, parents collected saliva cortisol samples at wakeup, midmorning, midafternoon, and evening for 2 days. In a finding similar to that shown by the laboratory data, the colic and control infants did not have different levels of daily average cortisol. These laboratory and home data provide no evidence of greater responsivity in the physiological substrate of difficult temperament for colic infants and are consistent with evidence of similarity in temperament once colic is resolved. At home, compared with control infants, colic infants did display a blunted rhythm in cortisol production. By diary, they also slept about 2 hr less per day than did control infants. Nighttime sleep was still significantly different when fussing/crying was statistically controlled. These data suggest that colic might be associated with a disruption or delay in the establishment of the circadian rhythm in activity of the hypothalamic-pituitary-adrenocortical axis and associated sleep-wake activity.     

Vagal Regulation in Breastfeeding Infants and Their Mothers

Consistent with the gustatory–vagal hypothesis, vagal stimulation during breastfeeding may contribute to infants' physiological regulatory development independent of caregiving effects. This study examined whether breastfeeding predicted 6‐month‐old infants' (N = 151) and their mothers' vagal regulation during the face‐to‐face still‐face (FFSF). Although breastfed and nonbreastfed infants showed expected vagal withdrawal during the Still‐Face episode, only breastfed infants showed continued withdrawal during the reunion episode, suggesting greater physiological mobilization to repair the interaction. Breastfeeding mothers showed higher vagal tone than nonbreastfeeding mothers at baseline, suggesting greater capacity for regulation, and throughout the FFSF, suggesting calmer states. Breastfeeding effects were independent of maternal sensitivity. Findings suggest that infants' and mothers' physiological regulation may be shaped by breastfeeding independently of associated social factors.