Somatotopic cord-to-muscle relations in efferent innervation of cat gastrocnemius.

SWETT, J. E., EARL ELDRED, AND J. S. BUCHWALD. Somatotopic cord-to-muscle relations in efferent innervation of cat gastrocnemius. Am. J. Physiol. 2 19(3) : 762-766. 1970.-Motor innervation to the medial gastrocnemius muscle (MG) was examined in cats by stimulating natural rootlets and teased filaments of the ventral roots, and observing the location of contraction areas on the exposed muscle surface. The limb was denervated, except for the MG muscle. Stimulation of rootlets in strict caudocranial sequence revealed an overlapping progression in the zones of contraction, which commenced at the medial boundary of the muscle and shifted across to the hilar margin. Some rootlets in the intermediate portions of the total distribution gave rise to contractions involving the whole surface of the muscle. It was concluded that more distinct somatotopic organization existed within motor outflow to the MG than has been demonstrated in the sensory inflow. Comparisons of efferent and afferent connections to the muscle and other muscles of the triceps complex were made.