Chronically isolated lumbar half spinal cord generates locomotor activities in the ipsilateral hindlimb of the cat.

The lumbar spinal cord of the cat was both hemisected (at L2 or L3) and longitudinally myelotomized in order to make half lumbar cord isolated from descending as well as contralateral impulses. The chronic cats recovered the ability to stand with their two forelimbs and a hindlimb, contralateral to the hemisection, 17.2 +/- 10.8 days after the operations. Two days later the hindlimb innervated by the isolated half lumbar cord regained walking capability. Phase relationships between the fore- and hindlimb muscles during locomotion were studied by recording EMGs from bilateral triceps brachii, vastus lateris and tibialis anterior muscles. Phase relationships between bilateral triceps brachii were 0.97 +/- 0.13 pi to 1.09 +/- 0.12 pi, indicating that the two forelimbs were stepping alternately and rhythmically. Phase relationships between bilateral vastus lateralis muscles were highly variable step by step, suggesting that the stepping of the hindlimb innervated by the isolated half lumbar cord was independently carried out, possibly evoked by peripheral receptors such as joint, muscle and cutaneous receptors.