Fig. 2.

Representative examples of respiratory modulated interneurons. A: 2 separate examples of recordings from neurons that appear to be synaptically antecedent to the phrenic motor pool (i.e., prephrenic) based on the results of spike triggered averaging (STA). Sorted waveforms (i.e., spikes) and raw unit bursting, along with the phrenic neurograms (∫Phr), are presented in the left column. The middle column shows waveform overlay plots and cycle-triggered histograms for each cell. The η² values (see materials and methods) are provided above the histogram. The panels on the right provide the output of STA of the integrated phrenic neurogram (∫Phr, top) and raw phrenic neurogram (Phr, bottom). For both the cells designated as “prephrenic,” a distinct peak can be seen in the STA result that is ∼7 ms from zero. The peak could be detected for STA performed on both the integrated and raw signal. B: an example of an expiratory modulated recording. Note the complete absence of STA peak for this cell.