Hippocampus brain tissue. Fluorescence light micrograph of a sagittal (side view) section through the hippocampus of a rat's brain showing the nerve cells within it. The hippocampus is a structure of the limbic system of the brain. There is a hippocampus in each cerebral hemisphere, and they are thought to be responsible for spatial awareness and the formation of memories. Different structures have been stained different colours: the nuclei of cells are orange and neurofilaments are blue. Neurofilaments are proteins found in the axons (output processes) of nerve cells.