Asynchronous maturation of pathways for impulses from muscle and skin receptors to the sensomotor cortex in rabbits.

A comparative analysis was undertaken of the functional and structural maturation of peripheral pathways for the conduction of afferent impulses to the sensomotor cortex from muscle and skin receptors of the sciatic nerve during postnatal ontogeny in rabbits. The criterion of functional maturity of the fibers was their sensitivity to the blocking action of procaine when applied to muscular and cutaneous nerves. Structural maturation of peripheral nerve fibers was determined by the degree of their myelination. Successive blocking of fibers of muscular and cutaneous nerves by procaine was shown to depress certain components of the cortical evoked potential. As the animal develops, the sensitivity of its nerve fibers to procaine and the configuration of the evoked response are modified. Different peripheral projections, maturing at different times, participate in the organization of individual components of the cortical evoked potentials. This also takes place during maturation of peripheral afferent projections from muscular and cutaneous receptors.