Odorant similarity in the mouse olfactory bulb

It is widely held that odorant chemical features are mapped onto the olfactory epithelium (1, 2) and bulb (3), such that similar odorants activate common receptors and glomeruli. After applying ultra-high-resolution calcium-indicator dependent imaging to the olfactory bulb, Ma et al. (4) failed to identify a correlation between odorant pairwise structural differences and pairwise neuronal response differences [figure 4E in Ma et al. (4)]. They concluded that, “response similarity was not dictated by structural similarity of the odors, and vice versa.”