The Olfactory Bulb: Coding and Processing of Odor Molecule Information

Abstract

Olfactory sensory neurons detect a large variety of odor molecules and send information through their axons to the olfactory bulb, the first site for the processing of olfactory information in the brain. The axonal connection is precisely organized so that signals from 1000 different types of odorant receptors are sorted out in 1800 glomeruli in the mouse olfactory bulb. Individual glomerular modules presumably represent a single type of receptor and are thus tuned to specific molecular features of odorants. Local neuronal circuits in the bulb mediate lateral inhibition among glomerular modules to sharpen the tuning specificity of output neurons. They also mediate synchronized oscillatory discharges among specific combinations of output neurons and may contribute to the integration of signals from distinct odorant receptors in the olfactory cortex.

Isolation and characterization of the laure olfactory behavioral mutant in the zebrafish, Danio rerio

“…In the olfactory system, axon guidance is a multi-step process with pioneer neurons initiating the connection between the developing olfactory placode and the telencephalon (Whitlock and Westerfield, 1998) and olfactory receptors contributing to the targeting of the axons to the glomeruli in the developing olfactory bulb (Lin and Ngai, 1999;Mori et al, 1999). Loss of pioneer neurons results in misrouting of the axons of the olfactory sensory neurons into neighboring commissures in the zebrafish (Whitlock and Westerfield, 1998).…”

“…Within the developing olfactory bulbs the sensory axons terminate in characteristic clusters called glomeruli, initially described over a century ago by Santiago Ramon y Cajal (Ramon y Cajal, 1897). These glomer-uli are formed in part by the convergence of axons from OSNs that express the same olfactory receptors (Mori et al, 1999). As the sensory system develops, the axons of the OSNs use multiple cues to guide their outgrowth from the sensory epithelium to the bulb.…”

Comparative analysis of the role of olfaction and the neocortex in primate intrasexual competition

“…The VNO is located at the base of the nasal cavity above the hard palate and the vomeronasal nerve projects to the accessory olfactory bulb (AOB) (Meredith, 1991;Meisami and Bhatnagar, 1998;Keverne, 1999;Smith et al, 2001). Within each system, the MOB and AOB are the first sites of processing within the brain (Mori et al, 1999). Although all primates have a functioning MOB, the AOB and VNO are absent in catarrhines, with the exception of vestiges of the VNO found in some hominoids Smith et al, 2001).…”

Synaptic Integration of Olfactory Information in Mouse Anterior Olfactory Nucleus

“…Previous studies show that mitral cells in the MOB are narrowly tuned, typically responding to odorants with high structural similarity (Mori, 1995;Mori et al, 1999) (I. Davison and L. C. Katz, unpublished observations). To confirm that the 40 structurally dissimilar odorants in our odor panel do indeed activate disparate mitral cells, we measured the suprathreshold and subthreshold responses of mitral cells to the same odorant panel used to assess AON neuronal responsiveness.…”