ABSTRACT
The olfactory pathways of terrestrial mammals are exceptional for their extraordinary plasticity. For most components of the adult nervous system, plasticity is limited to the standard capabilities of individual neurons such as extending and retracting axons and dendrites, changing synaptic strength, and regenerating severed processes. While this ordinary type of plasticity is important and interesting, it pales in comparison to the more global capabilities of the olfactory pathways. For example, the olfactory system of adults shows a unique ability to respond to and recover from trauma and sensory deprivation. This striking plasticity is largely attributable to the presence of stem cells, which normally supply replacements for certain neurons in the olfactory epithelia and bulbs. In response to trauma or deprivation, the production and survival of these stem cells can be increased or decreased. In many ways these properties of the adult olfactory system are reminiscent of those of the other sensory systems during development.
