Circuit formation and maintenance--perspectives from the mammalian olfactory bulb.

The rodent olfactory bulb (OB) is becoming a model system for studying how neuronal circuits develop and maintain. The OB has typical components of a sensory circuit such as ordered sensory inputs, diverse populations of interneurons, substantial neuromodulatory innervation, and projection neurons that transfer information to higher brain centers. Additionally, the OB is unique because its sensory afferents and a subset of its interneurons are continuously replaced throughout adulthood. Here, we review some recent findings on the development and maintenance of the mammalian OB circuitry. We review some of the known developmental strategies of the major OB components and discuss the ways in which the OB circuitry preserves stability in the face of ongoing changes.