Red nucleus: past and future.

The red nucleus has greatly interested scientists for almost a century. This can be explained by the fact that problems of general interest are encountered when studying this nucleus. Some of them are outlined in this paper, such as the phylogenetic evolution of the rubrospinal tract, the respective roles of the rubrospinal and pyramidal tracts in the execution of various types of movements, and the respective roles of these two tracts in movement automatization.