TOPOGRAPHIC ORGANIZATION OF SENSORY PROJECTIONS TO THE OLFACTORY-BULB

The detection of odorant receptor mRNAs within the axon terminals of s ensory neurons has permitted us to ask whether neurons expressing a gi ven receptor project their axons to common glomeruli within the olfact ory bulb. In situ hybridization with five different receptor probes de monstrates that axons from neurons expressing a given receptor converg e on one, or at most, a few glomeruli within the olfactory bulb. Moreo ver, the position of specific glomeruli is bilaterally symmetric and i s constant in different individuals within a species. These data suppo rt a model in which exposure to a given odorant may result in the stim ulation of a spatially restricted set of glomeruli, such that the indi vidual odorants would be associated with specific topographic patterns of activity within the olfactory bulb.