The ring is closed in front by the medial portion of the orbitofrontal cortex . Deep to the parahippocampal gyrus and running in parallel with it is the hippocampus . The hippocampus is the phylogenetically ancient part of the cortex and is also referred to as archicortex. The hippocampal formation is rolled in upon itself and cannot be seen from the surface of the brain. Although olfactory input constitutes only a small portion of the limbic afferents, the olfactory system is a useful way to begin studying the organization of the limbic system.
Axons leave the olfactory receptors and synapse in the olfactory bulb .
Consequently, neurons in the olfactory bulb called mitral cells represent secondary sensory neurons of the olfactory system. The olfactory tract is not a peripheral nerve. It is a tract of the central nervous system. The uncus is the rostral tip of the parahippocampal gyrus and the most medial part of the temporal lobe. The hypothalamus receives olfactory information through the amygdala.