The precentral sulcus lies parallel to, and in front of, the central sulcus. (A sulcus is one of the prominent grooves on the surface of the human brain. ) The precentral sulcus divides the inferior, middle, and superior frontal gyri from the precentral gyrus. In the majority of brains, the precentral sulcus is divided into two parts: the inferior precentral sulcus and the superior precentral sulcus. However, the precentral sulcus may also be divided into three parts or form one continuous sulcus. [ http://en.wikipedia.org/wiki/Precentral_sulcus ]