The term polymorphic layer of the dentate gyrus rrefers to the deepest of three subdivisions of the fascia dentata of the dentate gyrus based on cytoarchitecture. The more superficial subdivisions are the granular layer of the dentate gyrus and the molecular layer of the dentate gyrus.. It is found in the human ( Insausti-2012 ), macaque ( Petrides-2009 ), rat ( Swanson-2004 ) and mouse ( Hof-2000 ). In the rat and mouse, unlike the primates, the fascia dentata has three parts: the crest of the dentate gyrus, the medial blade of the dentate gyrus and the lateral blade of the dentate gyrus. Each has a polymorphic layer that is continuous with that of the others ( Swanson-2004 Hoff-2000 ). Updated 30 May 2024.