deepest and most prominent of the cortical sulci, extending from the anterior perforated substance first laterally at the deep incisure between the frontal and temporal lobes, then caudal and slightly posterior over the lateral aspect of the cerebral hemisphere; the superior temporal gyrus forms its lower bank, the insula its greatly expanded floor, and the frontal and parietal opercula its upper bank. The sulcus is composed of three portions, a large posterior ramus [TA] (ramus posterior [TA]) that is commonly called the lateral sulcus, a short anterior ramus [TA] (ramus posterior [TA]) located between the pars orbitalis and pars triangularis of the inferior frontal gyrus, and a short ascending ramus [TA] (ramus ascendens [TA]) located between the pars triangularis and pars opercularis. SYN: sulcus lateralis [TA], fissura cerebri lateralis, lateral cerebral fissure, sylvian fissure, fissure of Sylvius.