Psychophysiological correlates of infant temperament: stability of behavior and autonomic patterning from 5 to 18 months

The stability of infant temperament and autonomic patterning (heart period and cardiac vagal tone) was examined longitudinally when infants were 5, 10, and 18 months of age. Behavioral measures of reactivity and regulation to frustration tasks, and maternal perceptions of infant temperament were obtained at each age along with baseline measures of cardiac activity. No stability was found from 5 to 10 months while some stability of behavior and autonomic patterning was identified from 10 to 18 months, with the exception of negative reactivity. High levels of cardiac vagal tone (V) were associated with negative reactivity at 18 months. When examining groups based on degrees of reactivity and regulation, we found infants who responded negatively to frustration but who also displayed more regulatory behavior to have higher V.     

Infant reactivity: Physiological correlates of newborn and 5-month temperament.

The relation between measures of heart period and vagal tone and infant reactivity was investigated in a longitudinal study of infants from birth to 5 months of age. At 2 days of age, electrocardiogram (EKG) was recorded and a pacifier-withdrawal task was administered. At 5 months of age, EKG was recorded, after which infants and mothers participated in a laboratory session designed to elicit positive and negative reactivity. Maternal ratings of 5-month infant temperament were also obtained. There was a significant concurrent relation between 5-month vagal tone and negative reactivity elicited in the laboratory and maternal ratings of activity level and smiling behavior. Newborn vagal tone predicted maternal ratings of frustration and fear. Moderate stability was found for infant reactivity. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Infants' Vagal Regulation in the Still-Face Paradigm Is Related to Dyadic Coordination of Mother-Infant Interaction.

The authors investigated relations between mother-infant dyadic coordination and infants' physiological responses. Mothers (N=73) and 3-month-old male and female infants were observed in the still-face paradigm, and mothers' and infants' affective states were coded at 1-s intervals. Synchrony and levels of matching between mother-infant affective states were computed, and infants' heart rate and vagal tone were measured. Infants showed increased negative affect and heart rate and decreased vagal tone during mothers' still-face, indicating physiological regulation of distress. Infants who did not suppress vagal tone during the still-face (nonsuppressors) showed less positive affect, higher reactivity and vagal suppression in normal play and reunion episodes, and lower synchrony in normal play with mothers. The results indicate that infants' physiological regulation in social interaction differs in relation to dyadic coordination of affective behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral and heart rate pattern differences between breast-fed and bottle-fed neonates.

Behavioral and physiological differences between 61 breast-fed and 39 bottle-fed neonates were assessed between 17 and 56 hr postpartum (M age?=?37 hr). Ten minutes of baseline heart rate pattern and respiration data were recorded during sleep, and the Neonatal Behavioral Assessment Scale (NBAS) was administered subsequently. Perinatal and demographic information was collected by maternal interview and delivery records. Results indicate that breast-fed infants had significantly longer heart periods, elevated heart period variability, and higher vagal tone than bottle-fed infants. Behaviorally, breast-fed infants were significantly more irritable, more difficult to console, and more often unable to complete the alert orientation portion of the assessment. These results could not be attributed to perinatal status or maternal variables. These findings suggest that breast-feeding is associated not only with more optimal physiological organization in the early neonatal period, but also with increased irritable reactivity. The relevance of several nutritional and interactional factors is evaluated. The data indicate that method of feeding should be considered an important dimension in studies of neonatal functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reactivity and developmental competence in preterm and full-term infants.

Evaluated physiological and behavioral reactivity to a novel stimulus in 24 preterm and 24 full-term infants at 8 mo and examined its association with developmental competence. Infants who reacted to the stimulus with increased vagal tone more often engaged in focused examination and exhibited greater range in exploratory play than those whose vagal tone decreased in response to the stimulus. Some differences in developmental performance were detected based on term status. Preterm perinatal risk factors were inversely associated with exploratory examination and range. Results are discussed in terms of a challenge model for assessing behavioral and physiological functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental patterns of heart rate and variability in prematurely-born infants with apnea of prematurity

At equivalent post-conceptional ages, prematurely-born infants have higher heart rates and reduced heart rate variability, relative to full-term neonates. Premature birth might exert long-lasting effects on central and peripheral mechanisms that control cardiovascular activity. We assessed development of heart rate and heart rate variability in symptomatic preterm infants up to 6 months of age. Fifty 6.5-h evening recordings of EKG and breathing were obtained from prematurely-born infants (gestational ages: 24-35 weeks). Cardiac R-R intervals were captured with a resolution of +/- 0.5 msec. One-min epochs were selected from three periods of regular respiration in recordings from premature infants and 72 recordings of full-term infants at comparable post-conceptional ages. Mean heart rate and heart rate variability were determined for each recording. At 40 weeks post-conception, prematurely-born infants with apnea of prematurity showed higher heart rates and reduced heart rate variability than did full-term neonates. These differences between premature and full-term infants persisted throughout the next 6 months in those infants born prior to 30 weeks gestation, and in those infants born at 30-35 weeks who experienced respiratory distress syndrome (RDS) during the neonatal period. The findings suggest that premature delivery, or complications thereof, exerts long-lasting effects on cardiac control.     

Fetal antecedents of infant temperament

This study established the emergence of stable individual differences in neurobehavioral functioning prior to birth and examined their relation to subsequent infant temperament. Fetal heart rate and movement were recorded longitudinally for 31 fetuses at 6 gestational ages beginning at 20 weeks' gestation. Maternally reported temperament data were collected at 3 and 6 months. Moderate stability in all measures except reactivity was apparent at some time before birth. By 36 weeks, fetal neurobehavior accounted for between 22% and 60% of the variance in prediction of temperament scores. In general, more active fetuses were more difficult, unpredictable, unadaptable, and active infants. Higher fetal heart rate was associated with lower emotional tone, activity level, and predictability. We conclude that features of fetal neurobehavior provide the basis for individual differences in reactivity and regulation in infancy.     

Effect of roasted soybeans and corn on performance and ruminal and blood metabolites of dairy calves

Respiratory sinus arrhythmia (RSA) has been used as a non-invasive estimate of vagal tone to determine whether the reduction in resting heart rate commonly seen when humans are exposed to increases in the ambient pressure is associated with changes in vagal autonomic control. Two sets of divers (n = 4) were examined during two simulated saturation dives, one to 46 atmospheres absolute (ATA) and another to 37 ATA. A significant reduction in resting heart rate was seen in both dives upon exposure to high pressure compared with controls at 1 ATA. The reduction in heart rate seen at increased pressure was consistent regardless of respiratory rate, indicating that moderate changes in respiratory rate do not affect heart rate under these conditions. No changes in the overall magnitude of RSA were observed over a range of respiratory rates during either dive compared with control values at 1 ATA. During both dives, RSA was significantly larger (P < 0.05) at low respiratory rates compared with higher rates for both 1 ATA controls and at high pressure. The presence of a hyperbaric bradycardia strongly suggests that vagal tone is altered during hyperbaric exposure; however, the lack of change in the magnitude of RSA at high pressure brings into question the viability of using RSA as an accurate indicator of vagal tone and this lack of correspondence deserves further investigation.     

Increased heart rate in depressed subjects in spite of unchanged autonomic balance?

A clinical study was conducted to examine the effects of depression on cardiac autonomic control. Cardiac autonomic control was measured in 26 nonmedicated patients (19 females) suffering from Major Depression, melancholic type, and in 26 age- and sex-matched normal controls. We measured heart rate and high frequency heart rate variability (respiratory sinus arrhythmia), pulsewave velocity and blood pressure, during 10 min of supine rest under controlled conditions. Using a log transformed time domain measure of respiratory sinus arrhythmia (logRSA), we found an inverse linear dependence between cardiac vagal tone and age in the healthy subjects as well as the depressed patients. logRSA was 0.22+/-0.25 in the patients and 0.25+/-0.16 in the control group. While this difference was not significant (P > 0.1), the deviations from the regression line were significantly (P < 0.0005) greater in the patients (0.21+/-0.12) than in the control group (0.09+/-0.07), indicating a more heterogeneous vagal tone in the depressed patients. Heart rate was also significantly (P < 0.03) greater in the depressed patients (76.6+/-12.4) than in the control group (69.5+/-6.9). No between-group differences were found in pulsewave velocity or systolic blood pressure, but diastolic blood pressure was lower in depressed patients (73.5+/-8.7 vs. 80.8+/-9.1). We discuss the possibility that the increased heart rate seen in the absence of vagal tone changes may not be due to altered vagal or sympathetic tone, as measured in this study. Other factors, including altered autonomous heart rate, may be responsible for the higher heart rate in the depressed group.     

Child and mother cardiac vagal tone: Continuity, stability, and concordance across the first 5 years.

In this prospective longitudinal study, vagal tone and heart period were measured at 2 months and at 5 years in children and their mothers to evaluate the development of vagal regulation at rest and during an environmental task. Child baseline vagal tone and heart period were discontinuous; mother baseline vagal tone was discontinuous, but heart period was continuous. Group mean baseline-to-task change in vagal tone and heart period were continuous in both children and mothers. Children reached adult levels of baseline vagal tone by 5 years and did not differ from their mothers in baseline-to-task change in vagal tone or heart period. Baseline vagal tone tended to be stable, but baseline heart period and baseline-to-task change in vagal tone and heart period were unstable in children; both were stable in mothers. Baseline-to-task change in vagal tone showed consistent child–mother concordance. These findings contribute to understanding psychophysiological development. especially the ontogenesis of the vagal system and its regulatory capacity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for autonomic nervous system imbalance in women with irritable bowel syndrome

Autonomic nervous system function was assessed in women with and without irritable bowel syndrome using frequency domain measures of heart rate variability. Women were interviewed and placed into the irritable bowel syndrome (N = 25) group based on history of diagnosis and self-report of current gastrointestinal symptoms. Women in the control group denied a history of chronic gastrointestinal symptoms (N = 15). Women were followed for one menstrual cycle with a symptom diary, and during mid-luteal phase they wore a Holter 24-hr electrocardiograph monitor. Women with irritable bowel syndrome demonstrated significantly lower vagal tone as measured by the high frequency spectrum relative to control women. In addition, women with irritable bowel syndrome had a flattened 24-hr pattern of heart rate variability, with significantly lower levels of vagal tone during sleep. These results suggest that systemic sympathovagal balance may be shifted in a subset of women with irritable bowel syndrome.     

Heart rate variability and heart rate in healthy volunteers. Is the female autonomic nervous system cardioprotective?

AIMS: Heart rate variability has been proposed as an indicator of cardiovascular health. Since women have a lower cardiovascular risk, we hypothesized that there are gender differences in autonomic modulation. METHODS AND RESULTS: In 276 healthy subjects (135 women, 141 men) between 18 and 71 years of age, 24 h heart rate and heart rate variability were determined. All heart rate variability parameters, except for pNN50 and high frequency power, were higher in men. After adjustment for heart rate, we obtained gender differences for: the standard deviation (P=0.049), the standard deviation of the 5 min average (P=0.047), low frequency power (absolute values, P=0.002; normalized units, P<0.001) and ratio low frequency/high frequency (P<0.001). There were no significant gender differences in heart rate variability parameters denoting vagal modulation. Gender differences were confined to age categories of less than 40 years of age. The majority of heart rate variability parameters decreased with age. Only in men, was a higher body mass index associated with a higher heart rate and with lower heart rate variability parameters (P<0.001). CONCLUSION: Cardiac autonomic modulation as determined by heart rate variability, is significantly lower in healthy women compared to healthy men. We hypothesize that this apparently paradoxical finding may be explained by lower sympathetic activity (low frequency power) in women. This may provide protection against arrhythmias and against the development of coronary heart disease.     

Infant temperament and cardiac vagal tone: assessments at twelve weeks of age

Sixty 12-week-old infants participated in a laboratory study to explore the relations between temperament and cardiac vagal tone. Temperament was evaluated via laboratory observations and maternal ratings. Cardiac vagal tone, measured as the amplitude of respiratory sinus arrhythmia, was quantified from beat-to-beat heart period data collected during a resting baseline period and during the laboratory assessment of temperament. Specific hypotheses were investigated relating temperament to both basal cardiac vagal tone and changes in cardiac vagal tone during social/attention challenges. Infants with higher baseline cardiac vagal tone were rated in the laboratory as showing fewer negative behaviors and were less disrupted by the experimental procedure. Infants who decreased cardiac vagal tone during the laboratory assessment were rated on maternal report temperament scales as having longer attention spans, and being more easily soothed.     

Is there increased sympathetic activity in patients with hypertrophic cardiomyopathy?

OBJECTIVES: This study aimed to assess autonomic nervous system activity in patients with hypertrophic cardiomyopathy. BACKGROUND: Patients with hypertrophic cardiomyopathy are traditionally thought to have increased sympathetic activity. However, convincing evidence is lacking. METHODS: Heart rate variability was assessed from 24-h ambulatory electrocardiographic (Holter) recordings in 31 patients with hypertrophic cardiomyopathy and 31 age- and gender-matched normal control subjects in a drug-free state. Spectral heart rate variability was calculated as total (0.01 to 1.00 Hz), low (0.04 to 0.15 Hz) and high (0.15 to 0.40 Hz) frequency components using fast Fourier transformation analysis. RESULTS: There was a nonsignificant decrease in the total frequency component of heart rate variability in patients with hypertrophic cardiomyopathy compared with that of normal subjects (mean +/- SD 7.24 +/- 0.88 versus 7.59 +/- 0.57 ln[ms2], p = 0.072). Although there was no significant difference in the high frequency component (5.31 +/- 1.14 versus 5.40 +/- 0.91 ln[ms2], p = 0.730), the low frequency component was significantly lower in patients than in normal subjects (6.25 +/- 1.00 versus 6.72 +/- 0.61 ln[ms2], p = 0.026). After normalization (i.e., division by the total frequency component values), the low frequency component was significantly decreased (38 +/- 8% versus 43 +/- 8%, p = 0.018) and the high frequency component significantly increased (16 +/- 6% versus 12 +/- 6%, p = 0.030) in patients with hypertrophic cardiomyopathy. The low/high frequency component ratio was significantly lower in these patients (0.94 +/- 0.64 versus 1.33 +/- 0.55, p = 0.013). In patients with hypertrophic cardiomyopathy, heart rate variability was significantly related to left ventricular end-systolic dimension and left atrial dimension but not to maximal left ventricular wall thickness. No significant difference in heart rate variability was found between 14 victims of sudden cardiac death and 10 age- and gender-matched low risk patients. CONCLUSIONS: Our observations suggest that during normal daily activities, patients with hypertrophic cardiomyopathy experience a significant autonomic alteration with decreased sympathetic tone.     

Transmission electron microscopy studies of (111) twinned silver halide microcrystals

Minimal information is available on the autonomic response to exercise under adverse environmental conditions. Traditionally, pharmacological blockade has been used to study autonomic responsiveness but, owing to its invasive nature, such studies have been limited in their scope. Recent advances in electrocardiographic tape recording, telemetry and associated computing systems have provided investigators with noninvasive methods for assessing the autonomic response to various physiological stressors. This article describes methods for the analysis of heart rate variability (HRV) and discusses the reports of those who have used HRV analysis to evaluate autonomic regulation during exercise, heat exposure and the combination of these 2 stressors. Spectral analysis of HRV reduces variations in the R-R interval into component sine waves of differing amplitude and frequency. Amplitude (variance) is displayed as a function of frequency, and power (cumulative variance) is calculated for specified frequency ranges (< 0.03 Hz, 0.03 to 0.15 Hz and 0.15 to 0.5 Hz). Parasympathetic nervous system activity can be inferred from the several indices of high frequency power; however, the estimation of sympathetic nervous system activity from low frequency power is more problematic. Data on HRV have shown that sympathovagal regulation during exercise is dependent on the intensity of the activity and the environmental conditions. At the onset of exercise, heart rate is increased by a reduction in vagal tone and a temporary increase in sympathetic tone. A continuation of physical activity is associated with a continued withdrawal of vagal activity and an attenuation of sympathetic nervous system tone. However, with the additional stimulus of a heated environment, sympathetic activity remains increased throughout exercise.     

Influence of infarct-related artery patency on the indexes of parasympathetic activity and prevalence of late potentials in survivors of acute myocardial infarction

OBJECTIVES: The purpose of this study was to determine whether infarct-related coronary artery patency influences myocardial electrical stability as measured by the prevalence of late potentials or heart rate variability. BACKGROUND: Several studies have suggested that loss of vagal activity is associated with an increased incidence of arrhythmic death after myocardial infarction. METHODS: A short-duration, high resolution electrocardiogram (ECG) was performed before hospital discharge in 175 patients with a first myocardial infarction. Seventy-three patients received thrombolytic therapy. All patients underwent coronary angiography. Coronary occlusion was defined as minimal or no anterograde flow. Eighty-eight patients (50.3%) had an occluded infarct-related artery. Sixty-two healthy subjects served as control subjects to determine the normal range of heart rate variability. RESULTS: Comparison between the control group and patients without patency of the infarct-related artery in the time domain and spectral analyses revealed in the latter patients a reduced heart rate variability (p < 0.0001) and a lower power spectrum density in both the 0.05- to 0.15-Hz band (p < 0.0001) and the 0.15- to 0.35-Hz band (p < 0.0001). The heart rate variability in patients with late potentials was lower than in those with a normal signal-averaged ECG. Those patients with spontaneous or thrombolysis-induced reperfusion have less occurrence of late potentials and higher parasympathetic activity than do patients with a closed artery. CONCLUSIONS: This study suggests that the patency of the infarct-related artery determines both the absence of late potentials and the preservation of vagal tone and may explain the reduction in mortality induced by thrombolytic therapy in myocardial infarction.     

Circadian rhythm of heart rate variability is reversibly abolished in ischemic stroke

BACKGROUND AND PURPOSE: Acute brain infarction significantly decreases heart rate variability as a result of cardiovascular autonomic dysregulation. However, information regarding circadian rhythms of heart rate and heart rate variability is limited. METHODS: In this prospective study, we analyzed 24-hour circadian rhythm of heart rate and the time and frequency domain measures of heart rate variability in 24 patients with hemispheric brain infarction, 8 patients with medullary brainstem infarction, and 32 age- and sex-matched healthy control subjects. ECG data were obtained from the patients in the acute phase and at 6 months after the infarction. RESULTS: In the acute phase of stroke, all the components of heart rate variability, ie, standard deviation of RR intervals, total power, high-frequency power, low-frequency power, and very-low-frequency power, were similar at night (from midnight to 6 AM) and during the day (from 9 AM to 9 PM), indicating that the circadian oscillation of heart rate variability had been abolished. At 6 months after brain infarction, the circadian rhythm had returned and, as in the control subjects, the values at night were significantly higher than those in the daytime. The values in hemispheric and in brainstem infarction did not differ significantly from each other. CONCLUSIONS: These results suggest that circadian fluctuation of heart rate variability is reversibly abolished in the acute phase of ischemic stroke and that it returns during the subsequent 6 months. The loss of the relative vagal nocturnal dominance may contribute to the incidence of cardiac arrhythmias and other cardiovascular complications after acute stroke.     

Individual differences in emotion regulation and behavior problems in preschool children.

Emotion regulation (ER) was assessed during a negative mood induction in 79 preschoolers who varied in degree of behavior problems. Facial expressivity during the induction was used to identify 3 ER groups: inexpressive, modulated expressive, and highly expressive. Group differences in ER were significantly related to heart rate and skin conductance. Inexpressive preschoolers had the highest heart rate, lowest vagal tone, and smallest autonomic nervous system (ANS) change during the induction. Highly expressive preschoolers had the slowest heart rate, highest vagal tone, and largest ANS change. The inexpressive and highly expressive groups had more externalizing symptoms than the modulated group at preschool age and at follow-up at the end of 1st grade. Inexpressive preschoolers appeared to have more depressed and anxious symptoms at follow-up. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Children's emotion regulation: Self-report and physiological response to peer provocation.

The authors examined the notion that children's emotion regulation (ER) is a uniform skill by (a) investigating the concordance between self-report of ER and physiological measures and by (b) examining ER in a specific context (e.g., peer provocation) and context-free manner (e.g., during a semistructured interview of ER abilities). Seventy-two children in middle childhood (average age = 9 years) participated. Time-locked measures of heart rate reactivity and recovery were obtained in response to provoking comments, and vagal regulation was measured throughout the provocation session. Children who reported greater dysregulation showed increased heart rate reactivity to provocative comments (i.e., steeper heart rate slope) but no difference in heart rate recovery. The context-free but not the context-specific self-report measure was associated with a failure to suppress vagal tone. Implications for ER measurement and children's peer relations are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of alcohol on vagal regulation of cardiovascular function: Contributions of the polyvagal theory to the psychophysiology of alcohol.

Research was conducted to evaluate the influence of acute alcohol consumption on vagal regulation of heart rate. Nine men with histories of polydrug use participated in this residential study. On 5 separate days, they drank liquids consisting of cold water (on 2 days), a moderate dose of alcohol (0.64 g/kg), a high dose of alcohol (1.12 g/kg), and a placebo. Continuous recordings of heart period were quantified to produce 3 measures of heart rate variability, reflecting the amplitude of 3 neurophysiologically mediated rhythms. Heart period, respiratory rhythm (i.e., respiratory sinus arrhythmia [RSA]), and the 0.06–0.10-Hz vasomotor rhythm were significantly lower during the high alcohol dose condition, relative to the placebo and water conditions. Because the neural regulation of the heart by the vagus contributes to these variables, these findings suggest that alcohol reduces cardiac vagal tone. In support of this explanation, alcohol also decreased the coupling between changes in heart period and changes in RSA. This study demonstrated that alcohol produces a dysregulated state in which heart rate is relatively uncoupled from vagal activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)