Stephen W. Porges

Twenty very low birth weight (VLBW) children participated in a longitudinal follow-up study designed to explore the relation between neonatal physiological measures and school-age (6-9 years) outcome measures. Neonatal measures of mean heart period and cardiac vagal tone (respiratory sinus arrhythmia, RSA) were derived from weekly recordings at 33, 34, and 35 weeks gestational age. An RSA Maturation measure was calculated across the 3-week period to assess functional changes in vagal regulation of the heart during a period in which there is enhanced myelination of the vagus. In addition, the relation of neonatal risk measures (low birth weight, low socioeconomic status, high medical risk) and preschool measures (behavior, cognitive abilities) to school-age outcome measures was examined. As expected, school-age measures were closely related to preschool measures within the same domain. Neonatal risk measures were not related to school-age outcome measures. Of the neonatal physiological measures, RSA maturation was correlated with a single school-age measure, social competence as measured by the Child Behavior Checklist (Achenbach, 1988). Partial correlation and multiple regression analyses were used to further explore the relationship between neonatal RSA maturation and school-age social competence. Results support the hypothesis that early central nervous system self-regulatory abilities, as assessed by RSA measures, are predictive of later complex behaviors.

Real data often do not approximate the normal distribution. Under nonnormal conditions, psycho-physiologists who use parametric statistics may be testing with inadequate power and/or testing a measure of location (i.e., the mean) that does not represent the desired portion of the distribution for statistical comparison. The purpose of this paper is: first, to provide psycho-physiologists with a method to investigate group distributional characteristics; second, to evaluate the distributional characteristics of heart period and respiratory sinus arrhythmia in human adults and newborns; third, to demonstrate the increased statistical power that can accompany the selection of an alternative statistical analysis for nonnormal data. Suggestions are provided on how to analyze nonnormal data.

The use of respiratory sinus arrhythmia (RSA) is dependent on several quantification factors. The statistical consequences of sampling rate, R‐wave trigger accuracy, and the data structure of RSA estimates were evaluated via simulations and simulated modifications. Simulations demonstrated that sampling rate determined the amplitude of the smallest oscillation that could be accurately described. When the amplitude of the oscillation was smaller in milliseconds than the sampling interval, all smaller oscillations, regardless of amplitude, were indiscriminately assigned a default value defined as 50% of the sampling interval. Also, reduced R‐wave peak detection accuracy was demonstrated to influence statistical analyses. The distributional characteristics of several common methods of structuring RSA estimates were investigated, and results indicated that several methods result in asymmetrical distributions. We recommend using rapid sampling rates (i.e., 1 kHz), accurate R‐wave peak detectors, and avoiding statistical trouble.

The gustatory-vagal hypothesis proposes that gustatory stimulation elicits a coordinated vagal response manifested as an increase in ingestive behaviors (e.g., sucking) and a decrease in nucleus ambiguus vagal tone measured by decreases in the amplitude of respiratory sinus arrhythmia (RSA). The current study tested the gustatory-vagal hypothesis in a bottle feeding paradigm with 29 clinically stable, high-risk, low-birthweight neonates. The amplitude of respiratory sinus arrhythmia (RSA) was collected before, during, and after bottle feeding. Consistent with the gustatory-vagal hypothesis, RSA decreased during bottle feeding. In a longitudinal subsample of subjects, the pattern of RSA changes during the feeding paradigm was stable across two test sessions.

To investigate heart rate and respiratory sinus arrhythmia (RSA) as markers of developmental outcome, infant ECG and 3 year outcome were assessed in 41 very low birth weight (< 1,500 g) infants. Measures of mean heart rate and RSA, and the maturational shifts in their values from 33 to 35 weeks gestational age, were recorded. RSA measures predicted 3 year outcome beyond the effects of birth weight, medical risk, and socioeconomic status. Higher RSA was associated with better social skills, whereas greater RSA maturation was associated with better mental processing and gross motor skills. Lower heart rate was associated with better behavior regulation and social skills, whereas greater maturational decreases were associated with better gross motor skills. Dividing the sample into groups of infants with birth weights less than 1,000 g and those with birth weights over 1,000 g, RSA maturation emerged a strong predictor of mental processing, knowledge base, and gross motor skills in the former. A measure of joint maturation of RSA and heart rate was associated with better behavior regulation at 3 years, as measured by Child Behavior Checklist and Parenting Stress Index scores, for this group. The findings directly respond to the need for physiological variables in the prediction of outcome in high-risk infants.

Cardiac vagal tone is a construct that describes the functional relationship between the brainstem and the heart. Cardiac vagal tone is measured by quantifying the amplitude of respiratory sinus arrhythmia, a component of heart rate variability reflecting the functional output of vagal pathways on the heart. Although there is an extensive literature evaluating baseline vagal tone and its relation to behavior, the relation between individual differences in the ability to regulate cardiac vagal tone and behavior has been theoretically vague. This article introduces a theoretical model to explain the relation between vagal tone during steady states and vagal reactivity (i.e., the vagal brake) in response to environmental challenges. Based upon the proposed model, it was hypothesized that infants who had difficulties in regulating the vagal brake (i.e., decreasing cardiac vagal tone) during social/attention tasks would have difficulties developing appropriate social interactions requiring reciprocal engagement and disengagement strategies. Data from 24 infants are presented. The findings support the model and demonstrate that infants with difficulties in decreasing vagal tone during a social/attention task at 9 months of age had significantly more behavioral problems at 3 years of age. © 1996 John Wiley & Sons, Inc.

The model presented identifies the importance of neural regulation of autonomic state as an antecedent substrate for emotional, cognitive, and behavioral regulation. It is proposed that individual differences in neural regulation of autonomic state are related to normal and abnormal development. Establishing nervous system regulation of autonomic state is the infant's initial task of self-regulation. Survival for the high-risk infant is based primarily on physiological self-regulation. Although the methods described focus on the high-risk neonate, the model provides insight into normal development and may be generalized to the study of older children and adults with behavioral and psychological problems. Moreover, the model may contribute to assessment and intervention strategics for normal and abnormal development.

The vagus, the 10th cranial nerve, contains pathways that contribute to the regulation of the internal viscera, including the heart. Vagal efferent fibers do not originate in a common brainstem structure. The Polyvagal Theory is introduced to explain the different functions of the two primary medullary source nuclei of the vagus: the nucleus ambiguus (NA) and the dorsal motor nucleus (DMNX). Although vagal pathways from both nuclei terminate on the sinoatrial node, it is argued that the fibers originating in NA are uniquely responsible for respiratory sinus arrhythmia (RSA). Divergent shifts in RSA and heart rate are explained by independent actions of DMNX and NA. The theory emphasizes a phylogenetic perspective and speculates that mammalian, but not reptilian, brainstem organization is characterized by a ventral vagal complex (including NA) related to processes associated with attention, motion, emotion, and communication. Various clinical disorders, such as sudden infant death syndrome and asthma, may be related to the competition between DMNX and NA.

The developmental-structuralist approach to psychopathology in infants and young children involves studying adaptive and maladaptive patterns at each level of "experimental organization" from the early sensory, motor, and affective-thematic organizations to the later representational ones. Psychopathology may be related to defects or constrictions at each organizational level, including the representational or symbolic realm, without underlying vulnerabilities in earlier levels of organization, and may also involve the presumed "underbelly" of the personality, those central nervous system organizations that have to do with filtering and processing of perceptions and experience (the early sensory and affective-thematic organizations). The most severe psychopathologies, it will be suggested, occur where there are compromises in both the early sensory and affective-thematic and later representational organizations. Early limitations in "processing" animate or inanimate experiences may, in many instances, be highly specific and reversible rather than global. The early detection of sensory and affective-thematic organizational compromises, followed by approaches that facilitate phase-specific "essential experiences" through intact sensory pathways and the remediation of compromised ones, may provide a systematic base for possible preventive intervention approaches.