Propagation of voltage transients. Somatic to dendritic ratios of PSP amplitudes, half-widths and rise times were computed for each dendritic compartment, ratios were then weighted by the area of the compartments and distributions were standardized. Percentiles are shown as box plots (see insert) for amplitudes (A), half-widths (B) and rise times (C) respectively (boxes for cervical MNs are shaded). These percentiles were then weighted relative to the median and used as descriptors in cluster analysis. Dendrograms of cluster formations (using Pair group method) were based on ratios of amplitudes (D), half-widths (E) and rise times (F). A control, or middle level of synaptic background activity (Rmd = 20000 Ωcm2) was assumed in all cases shown. Labels starting with letters L and C stand for cervical and lumbar MNs respectively. The weighting factors for percentiles were: 0.33 for the 10th and 90th percentiles and 0.67 for the 25th and 75th percentiles.