A Mirror-Symmetric Excitatory Link Coordinates Odor Maps across Olfactory Bulbs and Enables Odor Perceptual Unity

• Published in: Neuron (Cambridge, Mass.) Vol. 99; no. 4; pp. 800 - 813.e6
• Main Authors: Grobman, Mark, Dalal, Tal, Lavian, Hagar, Shmuel, Ronit, Belelovsky, Katya, Xu, Fuqiang, Korngreen, Alon, Haddad, Rafi
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 22.08.2018; Elsevier Limited
• Subjects: Action Potentials - physiology; Animals; AONpE; bilateral information transfer; Cortex; Female; inter-hemispheric; Light; Lymphocytes; Male; Mice; Mice, Inbred CBA; Mice, Transgenic; Mirror Neurons - chemistry; Mirror Neurons - physiology; mirror-symmetric; Neural networks; Neurons; Odor; odor maps; Odorants; olfaction; Olfactory bulb; Olfactory Bulb - chemistry; Olfactory Bulb - cytology; Olfactory Bulb - physiology; Olfactory pathways; Olfactory Pathways - chemistry; Olfactory Pathways - cytology; Olfactory Pathways - physiology; optogenetics; perceptual unity; Random Allocation; Sensory evaluation; Smell - physiology; Software; perceptual unity; inter-hemispheric; optogenetics; olfaction; bilateral information transfer; odor; AONpE; odor maps; mirror-symmetric
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2018.07.012

Sensory input reaching the brain from bilateral and offset channels is nonetheless perceived as unified. This unity could be explained by simultaneous projections to both hemispheres, or inter-hemispheric information transfer between sensory cortical maps. Odor input, however, is not topographically organized, nor does it project bilaterally, making olfactory perceptual unity enigmatic. Here we report a circuit that interconnects mirror-symmetric isofunctional mitral/tufted cells between the mouse olfactory bulbs. Connected neurons respond to similar odors from ipsi- and contra-nostrils, whereas unconnected neurons do not respond to odors from the contralateral nostril. This connectivity is likely mediated through a one-to-one mapping from mitral/tufted neurons to the ipsilateral anterior olfactory nucleus pars externa, which activates the mirror-symmetric isofunctional mitral/tufted neurons glutamatergically. This circuit enables sharing of odor information across hemispheres in the absence of a cortical topographical organization, suggesting that olfactory glomerular maps are the equivalent of cortical sensory maps found in other senses. •Isofunctional mirror-symmetric M/T cells in the two olfactory bulbs are interconnected•M/T cells are interconnected via the anterior olfactory nucleus pars externa•This circuit enables odor information transfer between olfactory bulbs•This circuit may enable odor perceptual unity across hemispheres Grobman et al. report that isofunctional output neurons in the two olfactory bubs are interconnected and spatially mirror-symmetric. This circuit enables the sharing of odor information between hemispheres despite the lack of topographical organization of odor information in the cortex.