The term isthmus of the cingulate gyrus (ICG) refers to one of three components of the cingulate gyrus (CGG) in the human ( Carpenter-1983 ) and the macaque ( Martin-2000 ). The others are the anterior cingulate gyrus (ACG) and the posterior cingulate gyrus (PCG). Identified by dissection it is a small convolution on the mesial aspect of the cerebral hemisphere (CHS). In curving around the splenium of the corpus callosum (ccs) it connects the PCG dorsally and with the parahippocampal gyrus (PHG) ventrally. In some cases it is partially separated from the PHG by the anterior calcarine fissure (clfa), which also separates it from the lingual gyrus (LNG) caudally ( Duvernoy-1992 ). Its location in the macaque is similar except that its caudal boundary is with the cuneus (CUN) and is less well defined ( Martin-2000 ). Equivalent structures are not found in the smooth cerebral cortex (CTX) of the rat or mouse ( NeuroNames ). Updated 30 Oct 2024.