Fig. 4.

Respiratory patterns of RTN neurons. Respiratory patterns were classified according to the timing of the periods of reduced firing probability relative to the phrenic nerve discharge (PND). A: 3 most commonly encountered patterns, i.e., early-inspiratory (early-I) inhibition, twin inhibition during early-I and post-I phases, and post-inspiratory (post-I) inhibition; 2–3 examples of each class of neuron are represented to illustrate variations in the amplitude of the respiratory modulation. B: atypical RTN neurons (type 2) exhibiting maximum firing probability during early inspiration and nadir during postinspiration. Vertical lines identify the onset and termination of the inspiratory burst (expiration-inspiration and inspiration-postinspiration transitions) taking into consideration the smoothing effect (t = 0.05 s) of the PND integration procedure.