In the mouse olfactory bulb, information from sensory neurons is extensively processed by local interneurons before being transmitted to the olfactory cortex by mitral and tufted (M/T) cells. The precise function of these local networks remains elusive because of the vast heterogeneity of interneurons, their diverse physiological properties, and their complex synaptic connectivity. Here we identified the parvalbumin interneurons (PVNs) as a prominent component of the M/T presynaptic landscape by using an improved rabies-based transsynaptic tracing method for localcircuits. Invivo two-photon-targeted patch recording revealed that PVNs have exceptionally broad olfactory receptive fields and exhibit largely excitatory and persistent odor responses. Transsynaptic tracing indicated that PVNs receive direct input from widely distributed M/T cells. Both the anatomical and functional extent of this M/T→PVN→M/T circuit contrasts with the narrowly confined M/T→granule cell→M/T circuit, suggesting that olfactory information is processed by multiple local circuits operating at distinct spatial scales.
Bibliographical noteFunding Information:
We thank the Stanford Viral Core for help in generating AAVs, N. Uchida for reagents, C. Manalac for technical assistance, L. Cohen for assistance with electrophysiology, members of the Luo and Mizrahi Labs for discussion and critical reading of the manuscript, and T. Komiyama and J. Isaacson for communicating unpublished results. We thank D. Feldman and M. Feldman for financial support during the sabbatical of A.M. in the Luo Lab. K.M. is a Research Specialist and L.L. is an Investigator of the Howard Hughes Medical Institute. B.C.W. is an NSF Graduate Research Fellow and a Stanford Graduate Fellow. This work was also supported by a HHMI Collaborative Innovation Award, an NIH grant (R01-NS050835) to L.L., and a European Research Council Grant (number 203994) to A.M.