In this review there will be a description of the dentate gyrus (DG) neural circuitry that mediates the operation of a variety of mnemonic processes associated with dorsal and ventral DG function in rats. Dysfunction of the dorsal DG can be shown to mediate mnemonic processing of spatially based information including a) the operation of conjunctive encoding of multiple sensory inputs to determine spatial representations, b) pattern separation based on reducing interference between similar spatial locations and spatial contexts for horizontal distance between objects, vertical distance for height of objects, slope or angle of motor movements, c) importance of spatial context in object recognition and processing of shades of grey associated with the walls of the box d) temporal integration in the creation of remote memory based in part on DG neurogenesis and function of the CA3 subregion of the hippocampus. Dysfunction of the ventral DG can be shown to mediate mnemonic processing of odor and reward value based information including a) pattern separation for odors and reward value, and b) social recognition.