Saltatory conduction revealed by unidimensional latency-topography of peripheral nerve impulse

The ventral or dorsal root of the rat was placed on 12 electrodes arranged side by side at 0.4 mm intervals. Impulse conduction along the fiber was displayed using unidimensional latency-topography, which corresponds to the relation between latency and electrode distance. The relation revealed step-like displacement, which implies saltatory conduction of the impulse. Since the distance between the plateaux correspond to internodal length, the conduction velocity could be calculated from the length and the time differences between plateaux. It was found from 36 observations that : (i) mean internodal length was 0.92 +/- 0.13 mm (range 0.70--1.25 mm); (ii) mean conduction velocity was 76.1 +/- 20.7 m/s; and (iii) the correlation coefficient of conduction velocity and internodal length was statistically significant at r = 0.38 (P less than 0.025), so the longer the internodal length, the higher the conduction velocity.