scholarly journals Higher-order feature detection in olfactory bulb - Integration in the granule cell-mitral cell network

2012 ◽  
Vol 6 ◽  
Author(s):  
Schaefer Andreas
Keyword(s):  
Olfactory Bulb ◽  
Granule Cell ◽  
Feature Detection ◽  
Mitral Cell ◽  
Higher Order ◽  
Cell Network

Inhibition of Backpropagating Action Potentials in Mitral Cell Secondary Dendrites

2002 ◽  
Vol 88 (1) ◽  
pp. 64-85 ◽  
Author(s):  
Graeme Lowe
Keyword(s):  
Olfactory Bulb ◽  
Granule Cell ◽  
Action Potentials ◽  
Flash Photolysis ◽  
Glutamate Release ◽  
Mitral Cell ◽  
Repetitive Firing ◽  
Inhibitory Input ◽  
Mitral Cells ◽  
Distal Dendrite

The mammalian olfactory bulb is a geometrically organized signal-processing array that utilizes lateral inhibitory circuits to transform spatially patterned inputs. A major part of the lateral circuitry consists of extensively radiating secondary dendrites of mitral cells. These dendrites are bidirectional cables: they convey granule cell inhibitory input to the mitral soma, and they conduct backpropagating action potentials that trigger glutamate release at dendrodendritic synapses. This study examined how mitral cell firing is affected by inhibitory inputs at different distances along the secondary dendrite and what happens to backpropagating action potentials when they encounter inhibition. These are key questions for understanding the range and spatial dependence of lateral signaling between mitral cells. Backpropagating action potentials were monitored in vitro by simultaneous somatic and dendritic whole cell recording from individual mitral cells in rat olfactory bulb slices, and inhibition was applied focally to dendrites by laser flash photolysis of caged GABA (2.5-μm spot). Photolysis was calibrated to activate conductances similar in magnitude to GABAA-mediated inhibition from granule cell spines. Under somatic voltage-clamp with CsCl dialysis, uncaging GABA onto the soma, axon initial segment, primary and secondary dendrites evoked bicuculline-sensitive currents (up to −1.4 nA at −60 mV; reversal at ∼0 mV). The currents exhibited a patchy distribution along the axon and dendrites. In current-clamp recordings, repetitive firing driven by somatic current injection was blocked by uncaging GABA on the secondary dendrite ∼140 μm from the soma, and the blocking distance decreased with increasing current. In the secondary dendrites, backpropagated action potentials were measured 93–152 μm from the soma, where they were attenuated by a factor of 0.75 ± 0.07 (mean ± SD) and slightly broadened (1.19 ± 0.10), independent of activity (35–107 Hz). Uncaging GABA on the distal dendrite had little effect on somatic spikes but attenuated backpropagating action potentials by a factor of 0.68 ± 0.15 (0.45–0.60 μJ flash with 1-mM caged GABA); attenuation was localized to a zone of width 16.3 ± 4.2 μm around the point of GABA release. These results reveal the contrasting actions of inhibition at different locations along the dendrite: proximal inhibition blocks firing by shunting somatic current, whereas distal inhibition can impose spatial patterns of dendrodendritic transmission by locally attenuating backpropagating action potentials. The secondary dendrites are designed with a high safety factor for backpropagation, to facilitate reliable transmission of the outgoing spike-coded data stream, in parallel with the integration of inhibitory inputs.

Intracellular responses of identified rat olfactory bulb interneurons to electrical and odor stimulation

1990 ◽  
Vol 64 (3) ◽  
pp. 932-947 ◽  
Author(s):  
D. P. Wellis ◽  
J. W. Scott
Keyword(s):  
Electrical Stimulation ◽  
Olfactory Bulb ◽  
Granule Cell ◽  
Action Potentials ◽  
Granule Cells ◽  
Olfactory Nerve ◽  
Mitral Cell ◽  
Intracellular Recordings ◽  
Postsynaptic Potential ◽  
Stimulation Of

1. Intracellular recordings were made from 28 granule cells and 6 periglomerular cells of the rat olfactory bulb during odor stimulation and electrical stimulation of the olfactory nerve layer (ONL) and lateral olfactory tract (LOT). Neurons were identified by injection of horseradish peroxidase (HRP) or biocytin and/or intracellular response characteristics. Odorants were presented in a cyclic sniff paradigm, as reported previously. 2. All interneurons could be activated from a wide number of stimulation sites on the ONL, with distances exceeding their known dendritic spreads and the dispersion of nerve fibers within the ONL, indicating that multisynaptic pathways must also exist at the glomerular region. All types of interneurons also responded to odorant stimulation, showing a variety of responses. 3. Granule cells responded to electrical stimulation of the LOT and ONL as reported previously. However, intracellular potential, excitability, and conductance analysis suggested that the mitral cell-mediated excitatory postsynaptic potential (EPSP) is followed by a long inhibitory postsynaptic potential (IPSP). An early negative potential, before the EPSP, was also observed in every granule cell and correlated with component I of the extracellular LOT-induced field potential. We have interpreted this negativity as a "field effect," that may be diagnostic of granule cells. 4. Most granule cells exhibited excitatory responses to odorant stimulation. Odors could produce spiking responses that were either nonhabituating (response to every sniff) or rapidly habituating (response to first sniff only). Other granule cells, while spiking to electrical stimulation, showed depolarizations that did not evoke spikes to odor stimulation. These depolarizations were transient with each sniff or sustained across a series of sniffs. These physiological differences to odor stimulation correlated with granule cell position beneath the mitral cell layer for 12 cells, suggesting that morphological subtypes of granule cells may show physiological differences. Some features of the granule cell odor responses seem to correlate with some of the features we have observed in mitral/tufted cell intracellular recordings. Only one cell showed inhibition to odors. 5. Periglomerular (PG) cells showed a response to ONL stimulation that was unlike that found in other olfactory bulb neurons. There was a long-duration hyperpolarization after a spike and large depolarization or burst of spikes (20-30 ms in duration). Odor stimulation produced simple bursts of action potentials, Odor stimulation produced simple bursts of action potentials, suggesting that PG cells may simply follow input from the olfactory nerve.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Building a 3D model of the mitral-granule cell network in the olfactory bulb

2013 ◽  
Vol 7 ◽  
Author(s):  
Migliore Michele ◽  
Hines Michael ◽  
Cavarretta Francesco ◽  
Shepherd Gordon
Keyword(s):  
Olfactory Bulb ◽  
Granule Cell ◽  
3D Model ◽  
Cell Network

Group I Metabotropic Glutamate Receptors Are Differentially Expressed by Two Populations of Olfactory Bulb Granule Cells

2007 ◽  
Vol 97 (4) ◽  
pp. 3136-3141 ◽  
Author(s):  
Thomas Heinbockel ◽  
Kathryn A. Hamilton ◽  
Matthew Ennis
Keyword(s):  
Olfactory Bulb ◽  
Glutamate Receptors ◽  
Metabotropic Glutamate Receptors ◽  
Granule Cells ◽  
Mitral Cell ◽  
Mitral Cells ◽  
Patch Clamp Recording ◽  
Metabotropic Glutamate ◽  
Group I ◽  
Bath Application

In the main olfactory bulb, several populations of granule cells (GCs) can be distinguished based on the soma location either superficially, interspersed with mitral cells within the mitral cell layer (MCL), or deeper, within the GC layer (GCL). Little is known about the physiological properties of superficial GCs (sGCs) versus deep GCs (dGCs). Here, we used patch-clamp recording methods to explore the role of Group I metabotropic glutamate receptors (mGluRs) in regulating the activity of GCs in slices from wildtype and mGluR−/− mutant mice. In wildtype mice, bath application of the selective Group I mGluR agonist DHPG depolarized and increased the firing rate of both GC subtypes. In the presence of blockers of fast synaptic transmission (APV, CNQX, gabazine), DHPG directly depolarized both GC subtypes, although the two GC subtypes responded differentially to DHPG in mGluR1−/− and mGluR5−/− mice. DHPG depolarized sGCs in slices from mGluR5−/− mice, although it had no effect on sGCs in slices from mGluR1−/− mice. By contrast, DHPG depolarized dGCs in slices from mGluR1−/− mice but had no effect on dGCs in slices from mGluR5−/− mice. Previous studies showed that mitral cells express mGluR1 but not mGluR5. The present results therefore suggest that sGCs are more similar to mitral cells than dGCs in terms of mGluR expression.

scholarly journals Odor-evoked Increases in Olfactory Bulb Mitral Cell Spiking Variability

iScience ◽  
2021 ◽  
pp. 102946
Author(s):  
Cheng Ly ◽  
Andrea K. Barreiro ◽  
Shree Hari Gautam ◽  
Woodrow L. Shew
Keyword(s):  
Olfactory Bulb ◽  
Mitral Cell
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