Fig. 4.

Representative example of phrenic and XII neurograms (whole nerve recordings) and I XII MN bursting (single fiber recording) before, during, and after hypoxia. A: arterial blood pressure (BP) and both the raw and integrated phrenic and XII nerve signals. In addition, the discharge of a single I XII MN (XII MN) and its burst frequency (mean f, calculated in 100-ms bins) are shown in A, bottom. Hypoxia caused a progressive increase in phrenic and XII activity and a substantial increase in XII MN discharge frequency. Following hypoxia, phrenic and XII burst amplitude and I XII MN discharge frequency all remained elevated indicating posthypoxia short-term potentiation. B: expanded time scale traces showing a single neural breath from the areas marked in A, a–d. Both discharge frequency and spike numbers of I XII MNs were enhanced during and following hypoxia (B, b–d). Note that the I baseline pattern (Ba) transforms into an E-I pattern during hypoxia (Bc). To confirm that the recordings were from the same MN, the individual spikes from a–d are superimposed in Fig. 4B, bottom.