Intermediate zone and intermediate zone neurons. Do IZ neurons acts as pioneers for layer V neurons in rats?

It is assumed that pioneer neurons will predominantly show path finding ability, and that other neurons only follow the pioneer fibers. Here, tracers were injected into the newborn rat spinal cord followed by a search for labeled cells other than those in layer V. In all cases, neurons in the lower intermediate zone (IZ) of the dorsomedial cortex were retrogradely labeled. The IZ neurons have several characteristics required for pioneer neurons and project to the spinal cord first. Thus, the IZ neurons may function as pioneer neurons of the corticospinal projection and help in the formation of the permanent tract in rats.