outcome. However, not all high-risk preterm infants manifest poor outcomes. Similarly, infants diagnosed with regulatory disorders have been shown to have developmental deficits in childhood. But, again, not all infants with regulatory disorders demonstrate the same pattern of outcome. The model presented in this chapter suggests that measures of nucleus ambiguus vagal tone provide insight into physiological systems underlying complex behaviors. We have focused on interpreting the role of the nervous system in regulating physiological systems. For at-risk newborns, survival is based on their level of self-regulation. Moreover, in all infants, selfregulation of physiological systems provides the infrastructure for more complex levels of self-regulation of behavioral, social, emotional, and cognitive systems.
The assessment methods described in this chapter focus on a specific physiological system originating in the nucleus ambiguus. The nucleus ambiguus is a brain stem nucleus that coordinates sucking, swallowing, vocalizing, and breathing via vagal pathways. By monitoring RSA, it is possible to assess neural regulation competence. According to the hierarchical model, as proposed by Porges ( 1983), baseline measures of VNA assess the first level of competence, which is successful regulation of internal bodily process via neural negative-feedback systems. The vagal response to stimulation/stressors assesses the second level of competence, which is the balance between homeostatic demands and the demands of the stimuli/stressor. The assessment of each of these levels leads to conclusions regarding the likelihood of successful negotiation of the third and fourth levels of competence, reflecting observable behaviors and the coordination of behaviors, respectively. The review of the vagal tone/RSA literature, divided into neonatal and infant/toddler areas, provides evidence in support of the hierarchical model and the usefulness of VNA measures in the prediction of developmental outcome.
Preparation of this chapter and much of the research surveyed herein were supported in part by NICHD Grant HD22628 and Maternal and Child Health Bureau Grant MCJ240622 awarded to S. W. Porges.
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