Brodmann area 27 is a cytoarchitecturally defined cortical area that is a rostral part of the parahippocampal gyrus. It is commonly regarded as a synonym of presubiculum.
The dorsal part of the presubiculum is more commonly known as the postsubiculum, and is of interest because it contains head direction cells, which are responsive to the facing direction of the head.
The hippocampal formation is a compound structure in the medial temporal lobe of the brain. It forms a c-shaped bulge on the floor of the inferior horn of the lateral ventricle. Typically, the hippocampal formation is said to included the dentate gyrus, the hippocampus, and the subiculum. The presubiculum, parasubiculum, and the entorhinal cortex may also be included. The hippocampal formation is thought to play a role in memory, spatial navigation and control of attention. The neural layout and pathways within the hippocampal formation are very similar in all mammals.