Isthmus of cingulate gyrus
The cingulate gyrus commences below the rostrum of the corpus callosum, curves around in front of the genu, extends along the upper surface of the body, and finally turns downward behind the splenium, where it is connected by a narrow isthmus with the parahippocampal gyrus.This article incorporates text in the public domain from page 825 of the 20th edition of Gray's Anatomy (1918)