The objective is to identify brain structures which mediate controlling influences on breathing and blood pressure during waking and quiet sleep, and thus to assist determination of the mechanisms of failure in the Sudden Infant Death syndrome (SIDS). Blood oxygen level dependent (BOLD) functional magnetic resonance imaging will be used to visualize neural activity in 1) twenty-two patients with Congenital Central Hypoventilation Syndrome (CCHS), a disorder characterized by absence of central chemoreception, loss of breathing drive during sleep, impaired breathing responses to hyperthermia, and occasional waking hypotonia; 2) twnety-two Prader-Walli patients, who show diminished peripheral, but intact central chemoreception; and 3) twenty-two age- and gender-matched controls. Images will be acquired during baseline, and during hyperoxic, hypercapnic, hypoxic, inspiratory loading, hyperthermic, paced breathing and passive motion challenges, and during cold pressor application, while respiratory measures, heart rate and variability, non-invasive blood pressure, and an index of sympathetic outflow (sweating"""""""" are collected. Brain images from baseline conditions will be compare to images collected during experimental challenges in waking for all three groups, and in quiet sleep for CCHS and control subjects. The extent of activation and time course of changes in activated brain regions during challenges will be compared between groups. The timing of signal changes in different brain sites will be correlated with physiological changes accompanying the challengers. The studies have the potential to reveal the rain sites underlying breathing and blood pressure control, and the potential mechanisms of failure in SIDS.
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