Sister external tufted cells form dynamic intraglomerular ensembles representing odor identity and concentration

The olfactory system has been extensively studied from both anatomical and functional perspectives. The glomerular layer of the olfactory bulb is the first brain region to integrate olfactory signals, creating a topographic representation of odor identity. However, how sensory information-such as odor identity and concentration-is transformed within a glomerular unit remains unclear. To address this, we investigated how odor information is processed at the intraglomerular network level using genetic labeling, in vivo imaging, and computational methods. We showed that glomerular glutamatergic neurons, known as external tufted cells (ETCs), exhibit distinct responses to different odors and concentrations. Furthermore, in vivo structural and functional imaging of the sister ETCs revealed distinct intraglomerular neuronal ensembles influenced by odor identity and concentration. These findings suggest that ETCs could encode both odor identity and concentration simultaneously within glomerular modules, suggesting an early mechanism for odor decorrelation.