TY - JOUR T1 - Direct comparison of odor responses of homologous glomeruli in the medial and lateral maps of the mouse olfactory bulb JF - eneuro JO - eNeuro DO - 10.1523/ENEURO.0449-19.2020 SP - ENEURO.0449-19.2020 AU - Tokiharu Sato AU - Ryota Homma AU - Shin Nagayama Y1 - 2020/01/23 UR - http://www.eneuro.org/content/early/2020/01/23/ENEURO.0449-19.2020.abstract N2 - 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. This multiple glomerular representation of homologous inputs is considered to have more important functional roles for odor information processing than the redundant backup system. However, a consensus idea is lacking and this hinders interpretation of the phenomenon. In addition, the shared and unique odorant response properties of the homologous glomeruli remain unclear because the majority of medial glomeruli are hidden in the septal OB, and thus it is difficult to directly compare them. Olfactory sensory neurons, which express trace amine-associated odorant receptors (TAARs), were recently identified that project to a pair of glomeruli uniquely located in the dorsal OB. In this study, we measured the odorant-induced calcium responses of homologous pairs of TAAR glomeruli simultaneously in anesthetized mice and directly compared their response patterns. We found that they exhibited similar temporal response patterns and could not find differences in onset latency, rise time, decay time, or response amplitude. 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 of GABAergic, dopaminergic, and mitral/tufted cells, but not in presynaptic olfactory sensory axon terminals. This indicates that, at least in these TAAR glomeruli, the medial rather than the lateral OB map enhances the respiration-locked rhythm and transfers this information to higher brain centers.Significance Statement This study directly compared the odor-evoked responses in paired homologous glomeruli in medial and lateral maps in the mouse dorsal olfactory bulb using the in vivo calcium imaging technique, which revealed that the response amplitude, onset latency, rising time, and decay time were not significantly different between medial and lateral homologous glomeruli. However, postsynaptic but not presynaptic neuronal activity in medial glomeruli had stronger respiratory-locked calcium fluctuations than lateral glomeruli. These differences were also observed in the resting condition without odor stimulation. The results suggest that the medial map neurons enhance respiratory-linked odor representation and transmit it to higher brain centers. ER -