Reliability of respiratory sinus arrhythmia in R-R intervals, in 14-, 20-, and 26-week-old infants

Vagal tone during infant contingency learning and its disruption

This study used contingency learning to examine changes in infants' vagal tone during learning and its disruption. The heart rate of 160 five-month-old infants was recorded continuously during the first of two training sessions as they experienced an audiovisual event contingent on their pulling. Maternal reports of infant temperament were also collected. Baseline vagal tone, a measure of parasympathetic regulation of the heart, was related to vagal levels during the infants' contingency learning session, but not to their learner status. Vagal tone levels did not vary significantly over session minutes. Instead, vagal tone levels were a function of both individual differences in learner status and infant soothability. Vagal levels of infants who learned in the initial session were similar regardless of their soothability; however, vagal levels of infants who learned in a subsequent session differed as a function of soothability. Additionally, vagal levels during contingency disruption were significantly higher among infants in this group who were more soothable as opposed to those who were less soothable. The results suggest that contingency learning and disruption is associated with stable vagal tone in the majority of infants, but that individual differences in attention processes and state associated with vagal tone may be most readily observed during the disruption phase.

A multimethod assessment of anxiety and problem behavior in children with autism spectrum disorders and intellectual disability

Despite the increased risk for anxiety disorders in children with autism spectrum disorders (ASD), there is a lack of research on the assessment and treatment of anxiety in this population, particularly for those with an intellectual disability (ID). The present study evaluated a multimethod strategy for the assessment of anxiety and problem behavior in three children with ASD and ID. Anxiety was operationally defined using: (1) behavioral data from anxious behaviors, (2) affective/contextual data from parent-report and observer ratings of overall anxiety, and (3) physiological data (heart rate [HR] and respiratory sinus arrhythmia [RSA]). A functional assessment of problem behavior during high- and low-anxiety conditions was conducted. Higher levels of problem behavior and HR and lower RSA were found in the high-anxiety than in the low-anxiety conditions.

Behavioral and physiological responses to child-directed speech of children with autism spectrum disorders or typical development

Young boys with autism were compared to typically developing boys on responses to nonsocial and child-directed speech (CDS) stimuli. Behavioral (looking) and physiological (heart rate and respiratory sinus arrhythmia) measures were collected. Boys with autism looked equally as much as chronological age-matched peers at nonsocial stimuli, but less at CDS stimuli. Boys with autism and language age-matched peers differed in patterns of looking at live versus videotaped CDS stimuli. Boys with autism demonstrated faster heart rates than chronological age-matched peers, but did not differ significantly on respiratory sinus arrhythmia. Reduced attention during CDS may restrict language-learning opportunities for children with autism. The heart rate findings suggest that young children with autism have a nonspecific elevated arousal level.

Discriminative delay Pavlovian eyeblink conditioning in veterans with and without posttraumatic stress disorder

BACKGROUND

Impaired eyeblink (EB) classical conditioning using a delay paradigm has previously been shown in combat veterans, as well as in a group of depressed adults, compared to normal individuals. Significant deficits in immediate memory (IM) in combat PTSD+ veterans, compared to normal controls, have also been previously shown, but these differences became non-significant after controlling for level of self-reported depression. Furthermore, EB conditioning has been shown to be significantly correlated with heart rate variability (HRV) in normal adults. The present study examined how depression (self-reported), IM, and resting HRV are related to discriminative delay classical EB conditioning in veterans with and without PTSD.

METHOD

Three groups of subjects (combat PTSD+, combat PTSD-, and non-combat PTSD-) were assessed for self-report of depression and anxiety, as well as IM and HRV. Subjects received a single session of discriminative EB classical conditioning in which the conditioned stimulus (CS) was a light signal (either red or green) compounded with a tone. On CS+ trials, the light-tone compound stimulus co-terminated with a corneal airpuff (unconditioned stimulus, US), thus producing a delay paradigm. On CS- trials the appropriate light-tone stimulus was presented but not followed by the airpuff US. EB amplitude and frequency were recorded.

RESULTS

PTSD+ subjects had greater self-reported depression and anxiety scores than the two control groups, as well as lower scores on a measure of IM. However, the IM difference was not significant after the effects of self-reported depression and anxiety were controlled. EB CR amplitude was significantly greater to CS+ than CS- for all three groups. EB amplitude to both the US (airpuff) and the CS+ declined over trials, but was significantly lower in the combat PTSD+ group compared to the combined PTSD- groups. Subjects who reached an EB CR acquisition criterion had significantly greater scores on IM than those who did not reach criterion. Factor analysis of the entire data set revealed four factors corresponding to (1) self-reported depression and anxiety, (2) IM, (3) HRV, and (4) EB amplitude. EB frequency was significantly predicted by IM and HRV.

CONCLUSIONS

These data extend our previous results by showing deficits in EB conditioning among combat PTSD+ veterans that were associated with lower IM and resting HRV, but were not associated with self-report of depression.

Estimated cardiac vagal tone predicts fetal responses to mother's and stranger's voices

Heart rate responses of 84 near-term fetuses to recorded female voices were examined in 166 trials of auditory stimulation. Each fetus was presented with a 2-min recording of their mother's voice and a 2-min recording of a female stranger's voice, in counterbalanced order, with a 10-min rest period between trials. High frequency heart rate variability during a 2-min baseline period was used to estimate cardiac vagal tone for each trial. Differential heart rate responses to familiar and unfamiliar voice recordings were observed during a 2-min poststimulus period, only when estimated cardiac vagal tone was high. This finding suggests that vagal tone plays a moderating role in the cardiac responses of term fetuses to familiar and unfamiliar stimuli.

Respiratory sinus arrhythmia in blood phobic subjects

12 blood-phobic subjects, selected according to the Fear Survey Schedule and the Mutilation Questionnaire, and 50 control subjects performed a paced respiration task during which heart rate and respiration were recorded. Respiratory Sinus Arrhythmia (RSA) was analyzed as an autonomic index of vagal influence on the heart. Analysis showed a larger RSA in the blood-phobic group than the controls and points to a difference in vagal activity at rest between the groups.

Development of heart inter-beat interval variability in preweanling rats: effects of exposure to alcohol and hypoxia

The effect of alcohol exposure and hypoxia on the development of heart rate and heart inter-beat interval (IBI) variability was studied in preweanling rats. Rats were artificially reared from postnatal day (PD) 4 through 12 and either exposed to alcohol (5 g/kg/day) or hypoxia (2-15-min episodes/day) from PD 4 to 10. Control groups consisted of artificially reared and normally reared rats not exposed to alcohol or hypoxia. The heart rate and respiration was recorded for 20-min sessions every other day from PD 5 through 21. Inter-beat intervals and measures of their variability caused by respiratory sinus arrhythmia (RSA) were computed from the recordings. There was a steady decline in average IBI across this age range. There was little change in RSA from PD 5 to 15, followed by a large increase in RSA level from PD 15 to 21. The alcohol- and hypoxia-exposed rats showed significantly less increase in RSA level on PD 19 and 21. Large bradycardias occurred in all groups on PD 5, 9, and 17, and were more prevalent in rats exposed to alcohol or hypoxia. These data suggest that neural control of the chronotropic functions of the heart undergoes major changes in the late preweanling stage, and the changes in neural control are slowed by hypoxia or alcohol exposure during the early postnatal period.