Suprapontine control of respiration.
Despite focus on brainstem areas in central respiratory control, regions rostral to the medulla and pons are now recognized as being important in modulating respiratory outflow during various physiological states. The focus of this review is to highlight the role that suprapontine areas of the mammalian brain play in ventilatory control mechanisms. New imaging techniques have become invaluable in confirming and broadening our understanding of the manner in which the cerebral cortex of humans contributes to respiratory control during volitional breathing. In the diencephalon, the integration of respiratory output in relation to changes in homeostasis occurs in the caudal hypothalamic region of mammals. Most importantly, neurons in this region are strongly sensitive to perturbations in oxygen tension which modulates their level of excitation. In addition, the caudal hypothalamus is a major site for 'central command', or the parallel activation of locomotion and respiration. Furthermore, midbrain regions such as the periaqueductal gray and mesencephalic locomotor region function in similar fashion as the caudal hypothalamus with regard to locomotion and more especially the defense reaction. Together these suprapontine regions exert a strong modulation upon the basic respiratory drive generated in the brainstem.