Longitudinal fissure Longitudinal fissure The longitudinal fissure (or cerebral fissure, median longitudinal fissure, or interhemispheric fissure) is the deep groove that separates the two hemispheres of the vertebrate brain. The medial surfaces of the two hemispheres are as similarly convoluted by gyri and sulci as is the outer surface of the brain. It is thought that a majority of existing animals, including Homo sapiens, have evolved from a common wormlike ancestor that lived around 600 million years ago, called the urbilaterian. A bilaterian animal is one that has symmetrical left and right body halves. While it is still debated whether this species
Lateral sulcus point. The area lying around the Sylvian fissure is often referred to as the perisylvian cortex. The human secondary somatosensory cortex (S2, SII) is a functionally-defined region of cortex in the parietal operculum on the ceiling of the lateral sulcus. The cerebral cortex was not depicted in a realistic manner until the 17th century with the Sylvian fissure being first accurately painted by Girolamo Fabrici d'Acquapendente in 1600 to provide plates for his "Tabulae Pictae". Its first description is traditionally taken to be in 1641 by Caspar Bartholin who attributed its discovery to Franciscus Sylvius (1614–1672), professor of medicine at