Glomerulus-specific synchronization of mitral cells in the olfactory bulb

Odor elicits a well-organized pattern of glomerular activation in the olfac tory bulb. However, the mechanisms by which this spatial map is transformed into an odor code remain unclear. We examined this question in rat olfacto ry bulb slices in recordings from output mitral cells. Electrical stimulati on of incoming afferents elicited slow (similar to2 Hz) oscillations that o riginated in glomeruli and were highly synchronized for mitral cells projec ting to the same glomerulus. Cyclical depolarizations were generated by glu tamate activation of dendritic autoreceptors, while the slow frequency was determined primarily by the duration of regenerative glutamate release. Pat terned stimuli elicited stimulus-entrained oscillations that amplified weak and variable inputs. We suggest that these oscillations maintain the fidel ity of the spatial map by ensuring that all mitral cells within a glomerulu s-specific, network respond to odor as a functional unit.