Respiration can be modified by the central and the autonomic nervous systems. The respiratory centers in the medulla and pons contain neurons that fire spontaneously to initiate inspiration. In addition, respiration is modified by autonomic reflexes arising from the lungs, heart, blood vessels, and upper airways. For instance, central chemoreceptors (e.g., in the brainstem) are responsive to carbon dioxide concentrations, peripheral chemoreceptors near the large vessels of the heart are sensitive to oxygen concentrations in the blood, and stretch receptors in the lungs are sensitive to the extent of lung inflation.
Respiration is easily brought under voluntary control, and variations in respiration can produce changes in heart rate and electrodermal activity. Therefore, respiration needs to be monitored to determine whether responses to relevant and control questions are artifacts. For instance, a sharp sniff can reliably produce an electrodermal response. If an examinee were to sniff sharply following control but not relevant questions, it might appear that the individual’s responses to the relevant questions were relatively small and, therefore, reflected general stress, arousal, or anxiety rather than deception. In polygraph testing, the rate and depth of respiration are measured by strain gauges positioned around the chest and abdomen because breathing can produce fluctuations in the girth of either or both. The strain gauge provides a measure of relative amplitude; if the strain gauge moves during the session, amplitudes recorded prior to this movement could not be compared to those recorded following the movement.
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Cacioppo, J.T., G.G. Berntson, P.F. Binkley, K.S. Quigley, B.N. Uchino, and A. Fieldstone 1994 Autonomic cardiac control. II. Noninvasive indices and baseline response as revealed by autonomic blockades. Psychophysiology 31:586-598.
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