Anatomy and Neurobiology of the Main and Accessory Olfactory Bulbs

This chapter focuses on olfactory processing in the mammalian main olfactory bulb (MOB) and accessory olfactory bulb (AOB). The MOB is laminated with the layers forming concentric circles. These layers include: olfactory nerve layer (ONL), glomerular layer (GL), external plexiform layer (EPL), mitral cell layer (MCL), internal plexiform layer (IPL), granule cell layer (GCL), and the subependymal layer/subventricular zone. Unlike the MOB, the AOB does not receive input from the nasal epithelium: its sensory information comes from the vomeronasal organ (VNO). The most numerous class of cells in the external cellular layer (ECL) are the so-called mitral cells (MCs), the main projection neurons of the AOB. More broadly, several lines of evidence suggest that direct integration happens, but perhaps in only a minority of MCs.