Number of Calretinin-Containing Pyramidal Cells in Cingulate Cortex Layer V

Humans have an enlarged population calretinin-containing pyramidal cells in layer V of anterior cingulate cortex compared to other hominids. In most primates and rodents, the calcium-binding protein calretinin is expressed primarily by GABAergic interneurons and is not expressed by most populations of pyramidal cells. As described by Hof et al. (2001), great apes and humans have a small population of layer V pyramidal cells in the anterior cingulate cortex that express calretinin; these cells are more common in humans than in the other great apes. Pyramidal cells in the homologous cortical region of Old World monkeys, New World monkeys, and prosimian primates do not express calretinin. These cells are distinct from the Von Economo cells that are also present in anterior cingulate cortex.