Comparison in postnatal development between somatosensory and motor conduction in rabbits

A comparative study between the somatosensory-evoked cerebral potential (SEP) and motor cortex-evoked muscle response (MEMR), and between the sensory nerve action potential (SNAP) and peripheral nerve-evoked muscle response (M wave) was performed with respect to their maturational changes in the peak latencies, using 24 rabbits of ages of 10 to 180 days. The peak latencies of SEP, MEMR, SNAP and the M wave all decreased with an increase in age according to a hyperbolic curve of y = axb + c (b less than 0). The adult values of the peak latencies were reached simultaneously at 80 days of age for SEP and MEMR, and at 60 days of age for SNAP and the M wave. These findings indicate that the conduction of the somatosensory and motor pathways becomes fully maturated at the same time. On analysis of the differential coefficients on the above equation, some but substantial differences in the decrease rate of the peak latency were also found between SEP and MEMR, and between SNAP and the M wave. This suggests that there are also some differences in the maturational rate between the two pathways.