The olfactory bulb has one source of sensory input (axons from olfactory receptor neurons, and one output (mitral cell axons). It is thought that it functions as a filter. However, the olfactory bulb also gets "top-down" information from brain areas like the amygdala, neocortex, hippocampus, locus coeruleus, and substantia nigra.
Its range of functions probably include:
- discriminating between odors
- enhancing sensitivity of odor detection
- filtering out background odors
- permitting higher brain areas involved in arousal and attention to modify the detection or discrimination of odors.