Vagal Tone: A Physiological Marker of Stress
In order to maintain homeostasis, the central nervous system responds constantly, via neural feedback, to environmental cues. Stressful events disrupt the rhythmic structure of autonomic states, and subsequently, behaviors. Since the vagus plays such an integral role in the PNS via regulation of heart rate, it follows that the amplitude of respiratory sinus arrhythmia (RSA) is a good index of PNS activity via the cardiac vagus. That is, RSA is a measurable, noninvasive way to see how the vagus modulates heart rate activity in response to stress. This method is useful to measure individual differences in stress reactivity.
RSA is the widely used measure of the amplitude of heart rate rhythm associated with rate of spontaneous breathing. Research has shown that amplitude of RSA is an accurate indicator of the efferent influence of the vagus on the heart. Since inhibitory effects of the VVC branch of the vagus allow for a wide range of adaptive, prosocial behaviors, it has been theorized that individuals with greater vagal tone are able to exhibit a greater range of such behaviors. On the other hand, decreased vagal tone is associated with illnesses and medical complications that compromise the CNS. These complications may reduce one's capacity to respond to stress appropriately.
Read more about this topic: Polyvagal Theory
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