title: Task Learning Promotes Plasticity of Interneuron Connectivity Maps in the Olfactory Bulb.
abstract: Elucidating patterns of functional synaptic connectivity and deciphering mechanisms of how plasticity influences such connectivity is essential toward understanding brain function. In the mouse olfactory bulb (OB), principal neurons (mitral/tufted cells) make reciprocal connections with local inhibitory interneurons, including granule cells (GCs) and external plexiform layer (EPL) interneurons. Our current understanding of the functional connectivity between these cell types, as well as their experience-dependent plasticity, remains incomplete. By combining acousto-optic deflector-based scanning microscopy and genetically targeted expression of Channelrhodopsin-2, we mapped connections in a cell-type-specific manner between mitral cells (MCs) and GCs or between MCs and EPL interneurons. We found that EPL interneurons form broad patterns of connectivity with MCs, whereas GCs make more restricted connections with MCs. Using an olfactory associative learning paradigm, we found that these circuits displayed differential features of experience-dependent plasticity. Whereas reciprocal connectivity between MCs and EPL interneurons was nonplastic, the connections between GCs and MCs were dynamic and adaptive. Interestingly, experience-dependent plasticity of GCs occurred only in certain stages of neuronal maturation. We show that different interneuron subtypes form distinct connectivity maps and modes of experience-dependent plasticity in the OB, which may reflect their unique functional roles in information processing.
  
  
  
  Deducing how specific interneuron subtypes contribute to normal circuit function requires understanding the dynamics of their connections. In the olfactory bulb (OB), diverse interneuron subtypes vastly outnumber principal excitatory cells. By combining acousto-optic deflector-based scanning microscopy, electrophysiology, and genetically targeted expression of Channelrhodopsin-2, we mapped the functional connectivity between mitral cells (MCs) and OB interneurons in a cell-type-specific manner. We found that, whereas external plexiform layer (EPL) interneurons show broadly distributed patterns of stable connectivity with MCs, adult-born granule cells show dynamic and plastic patterns of synaptic connectivity with task learning. Together, these findings reveal the diverse roles for interneuons within sensory circuits toward information learning and processing.
authors: Department of Neuroscience.
authors: Longwen
authors: 0000-0002-4151-3676
authors: L
authors: Huang
authors: Program in Developmental Biology.
authors: Kevin
authors: K
authors: Ung
authors: Program in Developmental Biology, Medical Scientist Training Program.
authors: Isabella
authors: I
authors: Garcia
authors: Department of Molecular and Human Genetics, Baylor College of Medicine, and.
authors: Kathleen B
authors: KB
authors: Quast
authors: Department of Neuroscience.
authors: Keith
authors: K
authors: Cordiner
authors: Department of Neuroscience, Allen Institute for Brain Science, Seattle, Washington 98103.
authors: Peter
authors: 0000-0001-6809-462X
authors: P
authors: Saggau
authors: Department of Neuroscience, Program in Developmental Biology, Department of Molecular and Human Genetics, Baylor College of Medicine, and Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, Texas 77030, and arenkiel@bcm.edu.
authors: Benjamin R
authors: 0000-0001-9047-2420
authors: BR
authors: Arenkiel
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001245:Association Learning / Q000502:physiology*; D001931:Brain Mapping; D000075402:Channelrhodopsins; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials / Q000235:genetics / Q000502:physiology; D007395:Interneurons / Q000145:classification / Q000502:physiology*; D060850:LIM-Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008027:Light; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D009415:Nerve Net / Q000502:physiology*; D009433:Neural Inhibition / Q000235:genetics / Q000502:physiology; D009473:Neuronal Plasticity / Q000235:genetics / Q000502:physiology*; D009812:Odorants; D009830:Olfactory Bulb / Q000166:cytology*; D062308:Optogenetics; D018408:Patch-Clamp Techniques; D018800:Thy-1 Antigens / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D000075402:Channelrhodopsins; C501120:Dlx5 protein, mouse; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D018800:Thy-1 Antigens; D014157:Transcription Factors; C063843:insulin gene enhancer binding protein Isl-1; D049452:Green Fluorescent Proteins
keywords: circuit; interneuron; mitral; olfactory; optogenetics; plasticity