Abstract
We discovered a new type of dendritic spine. It is found on space-specific neurons in the barn owl inferior colliculus, a site of experience-dependent plasticity. Connectomic analysis revealed dendritic protrusions of unusual morphology including topological holes, hence termed “toric” spines (n = 76). More significantly, presynaptic terminals converging onto individual toric spines displayed numerous active zones (up to 49) derived from multiple axons (up to 11) with incoming trajectories distributed widely throughout 3D space. This arrangement is suited to integrate input sources. Dense reconstruction of two toric spines revealed that they were unconnected with the majority (∼84%) of intertwined axons, implying a high capacity for information storage. We developed an ex vivo slice preparation and provide the first published data on space-specific neuron intrinsic properties, including cellular subtypes with and without toric-like spines. We propose that toric spines are a cellular locus of sensory integration and behavioral learning.
Footnotes
The authors declare no competing financial interests.
This work was supported by National Institutes of Health Grants R01DC05640 (from NIDCD; to W.M.D.), BRAIN-STIM grant from the University of California Davis Office of Research and Behavioral Health Center for Excellence (W.M.D.), R01NS104911 (from the BRAIN Initiative; to W.M.D. and M.H.E.), P41GM103412 (for support of National Center for Molecular Imaging Research; to M.H.E.), 2018 NARSAD Young Investigator grant (E.G.A.), NSF1754831 and MH114178 (to D.F.), and a UCDMC Interdepartmental Grant (D.F. and W.M.D.).
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