The population of reticulospinal neurons of the hindbrain receives input from several brain regions and activates spinal interneurons that assemble stepping. Axons of these reticulospinal neurons descend in the ventral part of the lateral funiculus. Axons of certain spinal neurons form the “stepping strip” in the dorsal part of the lateral funiculus. Stimulation of this strip elicits stepping via particular spinal neurons that send their axons to the ventral part of the lateral funiculus. Neurons of these two types form the propriospinal system capable of activating spinal interneurons that assemble stepping.
Mark L. Shik is with the Department of Zoology, George S. Wise Faculty of Life -Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel.