The term mitral cell ensemble of the main olfactory bulb (MCEm) refers to one of two clusters of neurons in the main olfactory bulb (MOB) of the human, macaque, rat, and mouse ( Buck-2013 ). The other is the tufted cell ensemble of the main olfactory bulb ( TCE ). The MCEm differs from the TCE in that MCEm's receive input from a small number of main olfactory sensory neurons (OSNm) and transmit local oderant information received by a single olfactory glomerulus (OLGm), whereas TCE's, receive input from a number of OLGm's and transmit broad information about an oderant stimulus. "Both mitral and tufted cells project a single primary dendrite into a single glomerulus, where they receive synaptic inputs from the axons of olfactory sensory neurons and make reciprocal synapses with the dendrites of PG cells." ( Nagayama-2014 ). Parallel projections from MCEm's and TCE's connect directly through the olfactory tract (oltr) to the olfactory cortex (OTX) and through the olfactory limb of the anterior commissure (aca) to the MOB in the opposite cerebral hemisphere (CHS) ( Buck-2013 ). Functionally, the MOB plays a roll in oderant feature detection. It is a key structure in the system that mediates the perception of smells ( Buck-2013 ).