Fig. 7.

Relationship between discharge rate and axonal conduction velocity of inspiratory augmenting neurons. Mean number of spikes per burst under resting condition (averaged over 20 consecutive bursts) plotted against the conduction velocity of the spinal axon (25 mm estimated straight-line distance between stimulating and recording points divided by antidromic latency). n = 49 cells. The two cell clusters delineated by the average linkage method (see Materials and Methods) are identified by ● (high-threshold cells) and ○ (low-threshold neurons).