Abstract
Olfactory sensory neurons (OSN) in mice express only 1 of a possible 1,100 odor receptors (OR) and axons from OSNs expressing the same odor receptor converge into ∼2 of the 1,800 glomeruli in each olfactory bulb (OB) in mice; this yields a convergence ratio that approximates 2∶1, 2 glomeruli/OR. Because humans express only 350 intact ORs, we examined human OBs to determine if the glomerular convergence ratio of 2∶1 established in mice was applicable to humans. Unexpectedly, the average number of human OB glomeruli is >5,500 yielding a convergence ratio of ∼16∶1. The data suggest that the initial coding of odor information in the human OB may differ from the models developed for rodents and that recruitment of additional glomeruli for subpopulations of ORs may contribute to more robust odor representation.
Highlights
Central odor processing begins in olfactory bulb (OB) glomeruli where olfactory sensory neuron (OSN) axons converge and synapse onto projection neurons, mitral and tufted cells, and populations of interneurons, peri/juxtaglomerular cells
A comparable laminar organization is found in the human OB, it is less rigorous in the segregation of cell populations and often lacks the circumferential organization of layers found in rodents and the medial-lateral symmetry of the rodent OB (Fig. 1b,c)
Abundance of glomeruli in the human OB In rodents, coding of odor signals begins as OSN axons segregate into specific glomeruli in the OB [5,12,13]
Summary
Central odor processing begins in olfactory bulb (OB) glomeruli where olfactory sensory neuron (OSN) axons converge and synapse onto projection neurons, mitral and tufted cells, and populations of interneurons, peri/juxtaglomerular cells. Odor processing by the OB projection neurons, mitral/tufted cells, is regulated by OB interneurons; peri/juxtaglomerular (PG) cells form dendrodendritic synapses with the primary dendritic arbor of projection neurons, and granule cells with the secondary dendrites in the external plexiform layer (EPL) [9]. These largely inhibitory synapses contribute to the modulation of projection neuron output and local lateral inhibition. The ongoing replacement of these interneurons in the adult reflects the highly dynamic nature of the OB synaptic circuits and their capacity for plasticity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
