scholarly journals Flexible Representations of Odour Categories in the Mouse Olfactory Bulb

2020 ◽  
Author(s):  
Elena Kudryavitskaya ◽  
Eran Marom ◽  
David Pash ◽  
Adi Mizrahi
Keyword(s):  
Olfactory Bulb ◽  
Task Demands ◽  
Decision Boundary ◽  
Response Dynamics ◽  
Sensory Stimuli ◽  
Related Information ◽  
Categorical Representation ◽  
Odour Discrimination ◽  
Basic Features

SUMMARYThe ability to group sensory stimuli into categories is crucial for efficient interaction with a rich and ever-changing environment. In olfaction, basic features of categorical representation of odours were observed as early as in the olfactory bulb (OB). Categorical representation was described in mitral cells (MCs) as sudden transitions in responses to odours that were morphed along a continuum. However, it remains unclear to what extent such response dynamics actually reflects perceptual categories and decisions therein. Here, we tested the role of learning on category formation in the mouse OB, using in vivo two-photon calcium imaging and behaviour. We imaged MCs responses in naïve mice and in awake behaving mice as they learned two tasks with different classification logic. In one task, a 1-decision boundary task, animals learned to classify odour mixtures based on the dominant compound in the mixtures. As expected, categorical representation of close by odours, which was evident already in naïve animals, further increased following learning. In a second task, a multi-decision boundary task, animals learned to classify odours independent of their chemical similarity. Rather, odour discrimination was based on the meaning ascribed to them (either rewarding or not). Following the second task, odour representations by MCs reorganized according to the odour value in the new category. This functional reorganization was also reflected as a shift from predominantly excitatory odour responses to predominantly inhibitory odour responses. Our data shows that odour representations by MCs is flexible, shaped by task demands, and carry category-related information.

Phasic Stimuli Evoke Precisely Timed Spikes in Intermittently Discharging Mitral Cells

2004 ◽  
Vol 92 (2) ◽  
pp. 743-753 ◽  
Author(s):  
Ramani Balu ◽  
Phillip Larimer ◽  
Ben W. Strowbridge
Keyword(s):  
Olfactory Bulb ◽  
Action Potentials ◽  
Sensory Stimulation ◽  
Spike Timing ◽  
Mitral Cells ◽  
Potential Oscillations ◽  
Sensory Stimuli ◽  
Subthreshold Oscillations ◽  
Simple Step

Mitral cells, the principal cells of the olfactory bulb, respond to sensory stimulation with precisely timed patterns of action potentials. By contrast, the same neurons generate intermittent spike clusters with variable timing in response to simple step depolarizations. We made whole cell recordings from mitral cells in rat olfactory bulb slices to examine the mechanisms by which normal sensory stimuli could generate precisely timed spike clusters. We found that individual mitral cells fired clusters of action potentials at 20-40 Hz, interspersed with periods of subthreshold membrane potential oscillations in response to depolarizing current steps. TTX (1 μM) blocked a sustained depolarizing current and fast subthreshold oscillations in mitral cells. Phasic stimuli that mimic trains of slow excitatory postsynaptic potentials (EPSPs) that occur during sniffing evoked precisely timed spike clusters in repeated trials. The amplitude of the first simulated EPSP in a train gated the generation of spikes on subsequent EPSPs. 4-aminopyridine (4-AP)–sensitive K+ channels are critical to the generation of spike clusters and reproducible spike timing in response to phasic stimuli. Based on these results, we propose that spike clustering is a process that depends on the interaction between a 4-AP–sensitive K+ current and a subthreshold TTX-sensitive Na+ current; interactions between these currents may allow mitral cells to respond selectively to stimuli in the theta frequency range. These intrinsic properties of mitral cells may be important for precisely timing spikes evoked by phasic stimuli that occur in response to odor presentation in vivo.

scholarly journals Molecules, cells and networks involved in processing olfactory stimuli in the mouse olfactory bulb

e-Neuroforum ◽  
2011 ◽  
Vol 17 (3) ◽  
Author(s):  
T. Kuner ◽  
A. Schaefer
Keyword(s):  
Olfactory Bulb ◽  
Sensory Processing ◽  
Olfactory Conditioning ◽  
Sensory Stimuli ◽  
Slowing Down ◽  
Inhibitory Circuitry ◽  
Olfactory Stimuli ◽  
Odour Discrimination ◽  
Olfactory Processing ◽  
Conditioning Experiments

AbstractHow sensory stimuli are processed by neural networks is a key question of neurosci­ence. Olfactory conditioning experiments in mice demonstrated that odour processing is fast and stimulus-dependent. Selective ge­netic perturbation of the inhibitory circuitry in the first relay station of olfactory processing, the olfactory bulb, altered such discrim­ination times, with increased inhibition accelerating and decreased inhibition slowing down odour discrimination. This illustrates that inhibition fulfils a key role in sensory processing.

scholarly journals A Decade of Imaging Cellular Motility and Interaction Dynamics in the Immune System

Science ◽  
2012 ◽  
Vol 336 (6089) ◽  
pp. 1676-1681 ◽  
Author(s):  
Ronald N. Germain ◽  
Ellen A. Robey ◽  
Michael D. Cahalan
Keyword(s):  
Lymph Nodes ◽  
Live Cell Imaging ◽  
Quantitative Measurement ◽  
Cell Imaging ◽  
Plasma Cells ◽  
Effector T Cells ◽  
Cellular Interactions ◽  
Cellular Motility ◽  
Response Dynamics

To mount an immune response, lymphocytes must recirculate between the blood and lymph nodes, recognize antigens upon contact with specialized presenting cells, proliferate to expand a small number of clonally relevant lymphocytes, differentiate to antibody-producing plasma cells or effector T cells, exit from lymph nodes, migrate to tissues, and engage in host-protective activities. All of these processes involve motility and cellular interactions—events that were hidden from view until recently. Introduced to immunology by three papers in this journal in 2002, in vivo live-cell imaging studies are revealing the behavior of cells mediating adaptive and innate immunity in diverse tissue environments, providing quantitative measurement of cellular motility, interactions, and response dynamics. Here, we review themes emerging from such studies and speculate on the future of immunoimaging.

scholarly journals Functional Domains of the TOL Plasmid Transcription Factor XylS

2000 ◽  
Vol 182 (4) ◽  
pp. 1118-1126 ◽  
Author(s):  
Niilo Kaldalu ◽  
Urve Toots ◽  
Victor de Lorenzo ◽  
Mart Ustav
Keyword(s):  
Dna Binding ◽  
Transcriptional Activation ◽  
Dependent Manner ◽  
Tol Plasmid ◽  
Terminal Fragment ◽  
Central Regions ◽  
Basic Features ◽  
Regulatory Functions

ABSTRACT The alkylbenzoate degradation genes of Pseudomonas putida TOL plasmid are positively regulated by XylS, an AraC family protein, in a benzoate-dependent manner. In this study, we used deletion mutants and hybrid proteins to identify which parts of XylS are responsible for the DNA binding, transcriptional activation, and benzoate inducibility. We found that a 112-residue C-terminal fragment of XylS binds specifically to the Pm operator in vitro, protects this sequence from DNase I digestion identically to the wild-type (wt) protein, and activates the Pm promoter in vivo. When overexpressed, that C-terminal fragment could activate transcription as efficiently as wt XylS. All the truncations, which incorporated these 112 C-terminal residues, were able to activate transcription at least to some extent when overproduced. Intactness of the 210-residue N-terminal portion was found to be necessary for benzoate responsiveness of XylS. Deletions in the N-terminal and central regions seriously reduced the activity of XylS and caused the loss of effector control, whereas insertions into the putative interdomain region did not change the basic features of the XylS protein. Our results confirm that XylS consists of two parts which probably interact with each other. The C-terminal domain carries DNA-binding and transcriptional activation abilities, while the N-terminal region carries effector-binding and regulatory functions.

FosGFP expression does not capture a sensory learning-related engram in superficial layers of mouse barrel cortex

2021 ◽  
Vol 118 (52) ◽  
pp. e2112212118
Author(s):  
Jiseok Lee ◽  
Joanna Urban-Ciecko ◽  
Eunsol Park ◽  
Mo Zhu ◽  
Stephanie E. Myal ◽  
...  
Keyword(s):  
Pyramidal Neurons ◽  
Barrel Cortex ◽  
Sensory Information ◽  
Learning Task ◽  
Early Gene ◽  
Sensory Stimuli ◽  
Association Learning ◽  
Neural Ensembles ◽  
Dependent Learning

Immediate-early gene (IEG) expression has been used to identify small neural ensembles linked to a particular experience, based on the principle that a selective subset of activated neurons will encode specific memories or behavioral responses. The majority of these studies have focused on “engrams” in higher-order brain areas where more abstract or convergent sensory information is represented, such as the hippocampus, prefrontal cortex, or amygdala. In primary sensory cortex, IEG expression can label neurons that are responsive to specific sensory stimuli, but experience-dependent shaping of neural ensembles marked by IEG expression has not been demonstrated. Here, we use a fosGFP transgenic mouse to longitudinally monitor in vivo expression of the activity-dependent gene c-fos in superficial layers (L2/3) of primary somatosensory cortex (S1) during a whisker-dependent learning task. We find that sensory association training does not detectably alter fosGFP expression in L2/3 neurons. Although training broadly enhances thalamocortical synaptic strength in pyramidal neurons, we find that synapses onto fosGFP+ neurons are not selectively increased by training; rather, synaptic strengthening is concentrated in fosGFP− neurons. Taken together, these data indicate that expression of the IEG reporter fosGFP does not facilitate identification of a learning-specific engram in L2/3 in barrel cortex during whisker-dependent sensory association learning.

Sonic hedgehog-dependent emergence of oligodendrocytes in the telencephalon: evidence for a source of oligodendrocytes in the olfactory bulb that is independent of PDGFRα signaling

Development ◽  
2001 ◽  
Vol 128 (24) ◽  
pp. 4993-5004
Author(s):  
Nathalie Spassky ◽  
Katharina Heydon ◽  
Arnaud Mangatal ◽  
Alexandar Jankovski ◽  
Christelle Olivier ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Olfactory Bulb ◽  
Sonic Hedgehog ◽  
Hedgehog Signaling ◽  
Molecular Mechanisms ◽  
Cell Contact ◽  
Sonic Hedgehog Signaling ◽  
Oligodendrocyte Progenitors

Most studies on the origin of oligodendrocyte lineage have been performed in the spinal cord. By contrast, molecular mechanisms that regulate the appearance of the oligodendroglial lineage in the brain have not yet attracted much attention. We provide evidence for three distinct sources of oligodendrocytes in the mouse telencephalon. In addition to two subpallial ventricular foci, the anterior entopeduncular area and the medial ganglionic eminence, the rostral telencephalon also gives rise to oligodendrocytes. We show that oligodendrocytes in the olfactory bulb are generated within the rostral pallium from ventricular progenitors characterized by the expression of Plp. We provide evidence that these Plp oligodendrocyte progenitors do not depend on signal transduction mediated by platelet-derived growth factor receptors (PDGFRs), and therefore propose that they belong to a different lineage than the PDGFRα-expressing progenitors. Moreover, induction of oligodendrocytes in the telencephalon is dependent on sonic hedgehog signaling, as in the spinal cord. In all these telencephalic ventricular territories, oligodendrocyte progenitors were detected at about the same developmental stage as in the spinal cord. However, both in vivo and in vitro, the differentiation into O4-positive pre-oligodendrocytes was postponed by 4-5 days in the telencephalon in comparison with the spinal cord. This delay between determination and differentiation appears to be intrinsic to telencephalic oligodendrocytes, as it was not shortened by diffusible or cell-cell contact factors present in the spinal cord.

scholarly journals Statistical Comparison of Spike Responses to Natural Stimuli in Monkey Area V1 With Simulated Responses of a Detailed Laminar Network Model for a Patch of V1

2011 ◽  
Vol 105 (2) ◽  
pp. 757-778 ◽  
Author(s):  
Malte J. Rasch ◽  
Klaus Schuch ◽  
Nikos K. Logothetis ◽  
Wolfgang Maass
Keyword(s):  
Network Model ◽  
Network Models ◽  
Cortical Network ◽  
Inhibitory Neurons ◽  
Sensory Stimuli ◽  
Natural Stimuli ◽  
Cortical Areas ◽  
Model Response ◽  
Spiking Activity

A major goal of computational neuroscience is the creation of computer models for cortical areas whose response to sensory stimuli resembles that of cortical areas in vivo in important aspects. It is seldom considered whether the simulated spiking activity is realistic (in a statistical sense) in response to natural stimuli. Because certain statistical properties of spike responses were suggested to facilitate computations in the cortex, acquiring a realistic firing regimen in cortical network models might be a prerequisite for analyzing their computational functions. We present a characterization and comparison of the statistical response properties of the primary visual cortex (V1) in vivo and in silico in response to natural stimuli. We recorded from multiple electrodes in area V1 of 4 macaque monkeys and developed a large state-of-the-art network model for a 5 × 5-mm patch of V1 composed of 35,000 neurons and 3.9 million synapses that integrates previously published anatomical and physiological details. By quantitative comparison of the model response to the “statistical fingerprint” of responses in vivo, we find that our model for a patch of V1 responds to the same movie in a way which matches the statistical structure of the recorded data surprisingly well. The deviation between the firing regimen of the model and the in vivo data are on the same level as deviations among monkeys and sessions. This suggests that, despite strong simplifications and abstractions of cortical network models, they are nevertheless capable of generating realistic spiking activity. To reach a realistic firing state, it was not only necessary to include both N -methyl-d-aspartate and GABAB synaptic conductances in our model, but also to markedly increase the strength of excitatory synapses onto inhibitory neurons (>2-fold) in comparison to literature values, hinting at the importance to carefully adjust the effect of inhibition for achieving realistic dynamics in current network models.

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