Fig. 7. Two example experiments in which the extracellular spike amplitudes, orthodromic conduction delays and response properties of many depressor motor neurons (Dep MN) were characterized. (A) 12 depressor motor neurons (Dep MN) were characterized. (Ai) The amplitude of the extracellular spike varies continuously. Spike amplitudes were normalized to the largest amplitude found in a given experiment. The neurons showed a resistance (R) reflex, and assistance (A) reflex, or no (N) response to movements imposed on the CBCO strand. Neurons received monosynaptic EPSPS (E), polysynaptic EPSPs (P), and IPSPs (I). (Aii) The neurons with the smallest spikes have the longest orthodromic delays. (Aiii) Conduction velocity was calculated for each neuron by dividing the distance between the neuropil and the site of the extracellular recording (7.5 mm) by the orthodromic delay. Conduction velocity varied with extracellular spike amplitude. (B) In a second experiment, we recorded from nine depressor motor neurons with similar trends to those found in the first experiment.