Comparison of odor responses of homologous medial and lateral glomeruli mapped in the olfactory bulb of the mouse

Olfactory sensory neurons expressing same-type odorant receptors typically project to a pair of glomeruli in the medial and lateral sides of the olfactory bulbs (OBs) in rodents. However, their functional properties remain unclear, because the majority of medial glomeruli are hidden in the septal OB. Recently, trace amine-associated odorant receptors were identified that project to a pair of glomeruli uniquely located in the dorsal OB. We measured the odorant-induced calcium responses of these glomeruli simultaneously and found that they exhibited similar temporal response patterns. However, the medial glomeruli had significantly larger respiration-locked calcium fluctuations than the lateral glomeruli. This trend was observed with/without odorant stimulation in postsynaptic neurons but not in presynaptic sensory axon terminals. This indicates that the medial rather than the lateral OB map enhances the respiration-locked rhythm and transfers this information to higher brain centers.\n\nImpact StatementThis study used in vivo calcium imaging to document the odor-evoked responses in paired glomeruli, demonstrating that activation in medial glomeruli more strongly impacts respiratory-linked odor processing.