Figure 1.

(A) Left to right, the steps of the respiratory control in human perinatal life. (1) In the human fetus, episodic respiratory activity aimed at promoting lung development is generated by the intermediolateral nucleus (ILN) in the upper spinal cord. (2) At the same time, during intrauterine life, the Kölliker–Fuse nucleus (KFN), located in the rostral pons, plays an important function by inhibiting the response of central and peripheral chemoreceptors and therefore any respiratory reflex, while allowing the occasional breathing activity headed by the ILN. (3) The facial/parafacial complex (F/PFC), in the caudal pons, starts working at birth, under the stimulation of the KFN, which drastically changes its function, giving rise to the first inspiratory act. The activity of the F/PFC is called “pre-inspiratory” because it is limited to activating, in its turn, the proper inspiratory nucleus in the medulla oblongata: the pre-Bötzinger nucleus (pBN) (4), responsible for starting postnatal breathing. (B) Brainstem schematic representation showing the localization of the RN components.