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Paoli M, Wystrach A, Ronsin B, Giurfa M. Analysis of fast calcium dynamics of honey bee olfactory coding. eLife 2024; 13:RP93789. [PMID: 39235447 PMCID: PMC11377060 DOI: 10.7554/elife.93789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/06/2024] Open
Abstract
Odour processing exhibits multiple parallels between vertebrate and invertebrate olfactory systems. Insects, in particular, have emerged as relevant models for olfactory studies because of the tractability of their olfactory circuits. Here, we used fast calcium imaging to track the activity of projection neurons in the honey bee antennal lobe (AL) during olfactory stimulation at high temporal resolution. We observed a heterogeneity of response profiles and an abundance of inhibitory activities, resulting in various response latencies and stimulus-specific post-odour neural signatures. Recorded calcium signals were fed to a mushroom body (MB) model constructed implementing the fundamental features of connectivity between olfactory projection neurons, Kenyon cells (KC), and MB output neurons (MBON). The model accounts for the increase of odorant discrimination in the MB compared to the AL and reveals the recruitment of two distinct KC populations that represent odorants and their aftersmell as two separate but temporally coherent neural objects. Finally, we showed that the learning-induced modulation of KC-to-MBON synapses can explain both the variations in associative learning scores across different conditioning protocols used in bees and the bees' response latency. Thus, it provides a simple explanation of how the time contingency between the stimulus and the reward can be encoded without the need for time tracking. This study broadens our understanding of olfactory coding and learning in honey bees. It demonstrates that a model based on simple MB connectivity rules and fed with real physiological data can explain fundamental aspects of odour processing and associative learning.
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Affiliation(s)
- Marco Paoli
- Neuroscience Paris-Seine - Institut de biologie Paris-Seine, Sorbonne Université, INSERM, CNRS, Paris, France
- Centre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative, Université Paul Sabatier, CNRS, Toulouse, France
| | - Antoine Wystrach
- Centre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative, Université Paul Sabatier, CNRS, Toulouse, France
| | - Brice Ronsin
- Centre de Biologie Intégrative, Université Paul Sabatier, CNRS, Toulouse, France
| | - Martin Giurfa
- Neuroscience Paris-Seine - Institut de biologie Paris-Seine, Sorbonne Université, INSERM, CNRS, Paris, France
- Centre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative, Université Paul Sabatier, CNRS, Toulouse, France
- Institut Universitaire de France (IUF), Paris, France
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2
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Lewis SM, Suarez LM, Rigolli N, Franks KM, Steinmetz NA, Gire DH. The spiking output of the mouse olfactory bulb encodes large-scale temporal features of natural odor environments. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.01.582978. [PMID: 38496526 PMCID: PMC10942328 DOI: 10.1101/2024.03.01.582978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
In natural odor environments, odor travels in plumes. Odor concentration dynamics change in characteristic ways across the width and length of a plume. Thus, spatiotemporal dynamics of plumes have informative features for animals navigating to an odor source. Population activity in the olfactory bulb (OB) has been shown to follow odor concentration across plumes to a moderate degree (Lewis et al., 2021). However, it is unknown whether the ability to follow plume dynamics is driven by individual cells or whether it emerges at the population level. Previous research has explored the responses of individual OB cells to isolated features of plumes, but it is difficult to adequately sample the full feature space of plumes as it is still undetermined which features navigating mice employ during olfactory guided search. Here we released odor from an upwind odor source and simultaneously recorded both odor concentration dynamics and cellular response dynamics in awake, head-fixed mice. We found that longer timescale features of odor concentration dynamics were encoded at both the cellular and population level. At the cellular level, responses were elicited at the beginning of the plume for each trial, signaling plume onset. Plumes with high odor concentration elicited responses at the end of the plume, signaling plume offset. Although cellular level tracking of plume dynamics was observed to be weak, we found that at the population level, OB activity distinguished whiffs and blanks (accurately detected odor presence versus absence) throughout the duration of a plume. Even ~20 OB cells were enough to accurately discern odor presence throughout a plume. Our findings indicate that the full range of odor concentration dynamics and high frequency fluctuations are not encoded by OB spiking activity. Instead, relatively lower-frequency temporal features of plumes, such as plume onset, plume offset, whiffs, and blanks, are represented in the OB.
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Affiliation(s)
- Suzanne M. Lewis
- Department of Psychology, University of Washington, Seattle, WA, United States
- Department of Neurobiology, Duke University, Durham, NC, USA
| | - Lucas M. Suarez
- Department of Psychology, University of Washington, Seattle, WA, United States
| | - Nicola Rigolli
- Laboratoire de Physique, École Normale Supérieure (LPENS), Paris, France
| | - Kevin M. Franks
- Department of Neurobiology, Duke University, Durham, NC, USA
| | - Nicholas A. Steinmetz
- Department of Biological Structure, University of Washington, Seattle, WA, United States
| | - David H. Gire
- Department of Psychology, University of Washington, Seattle, WA, United States
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3
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Ling D, Moss EH, Smith CL, Kroeger R, Reimer J, Raman B, Arenkiel BR. Conserved neural dynamics and computations across species in olfaction. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.24.538157. [PMID: 37162844 PMCID: PMC10168254 DOI: 10.1101/2023.04.24.538157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Interpreting chemical information and translating it into ethologically relevant output is a common challenge of olfactory systems across species. Are computations performed by olfactory circuits conserved across species to overcome these common challenges? To understand this, we compared odor responses in the locust antennal lobe (AL) and mouse olfactory bulb (OB). We found that odors activated nearly mutually exclusive neural ensembles during stimulus presentation ('ON response') and after stimulus termination ('OFF response'). Strikingly, ON and OFF responses evoked by a single odor were anticorrelated with each other. 'Inverted' OFF responses enhanced contrast between odors experienced close together in time. Notably, OFF responses persisted long after odor termination in both AL and OB networks, indicating a form of short-term memory. Taken together, our results reveal key neurodynamic features underlying olfactory computations that are conserved across insect and mammalian olfactory systems.
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Affiliation(s)
- Doris Ling
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO
| | - Elizabeth H Moss
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX
| | - Cameron L Smith
- Department of Neuroscience, Baylor College of Medicine, Houston TX
| | - Ryan Kroeger
- Department of Neuroscience, Baylor College of Medicine, Houston TX
| | - Jacob Reimer
- Department of Neuroscience, Baylor College of Medicine, Houston TX
| | - Baranidharan Raman
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO
| | - Benjamin R Arenkiel
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX
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4
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Gmaz JM, van der Meer MAA. Context coding in the mouse nucleus accumbens modulates motivationally relevant information. PLoS Biol 2022; 20:e3001338. [PMID: 35486662 PMCID: PMC9094556 DOI: 10.1371/journal.pbio.3001338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 05/11/2022] [Accepted: 04/04/2022] [Indexed: 11/18/2022] Open
Abstract
Neural activity in the nucleus accumbens (NAc) is thought to track fundamentally value-centric quantities linked to reward and effort. However, the NAc also contributes to flexible behavior in ways that are difficult to explain based on value signals alone, raising the question of if and how nonvalue signals are encoded in NAc. We recorded NAc neural ensembles while head-fixed mice performed an odor-based biconditional discrimination task where an initial discrete cue modulated the behavioral significance of a subsequently presented reward-predictive cue. We extracted single-unit and population-level correlates related to the cues and found value-independent coding for the initial, context-setting cue. This context signal occupied a population-level coding space orthogonal to outcome-related representations and was predictive of subsequent behaviorally relevant responses to the reward-predictive cues. Together, these findings support a gating model for how the NAc contributes to behavioral flexibility and provide a novel population-level perspective from which to view NAc computations.
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Affiliation(s)
- Jimmie M. Gmaz
- Department of Psychological and Brain Sciences, Dartmouth College, Hanover, United States of America
| | - Matthijs A. A. van der Meer
- Department of Psychological and Brain Sciences, Dartmouth College, Hanover, United States of America
- * E-mail:
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5
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Hardstone R, Zhu M, Flinker A, Melloni L, Devore S, Friedman D, Dugan P, Doyle WK, Devinsky O, He BJ. Long-term priors influence visual perception through recruitment of long-range feedback. Nat Commun 2021; 12:6288. [PMID: 34725348 PMCID: PMC8560909 DOI: 10.1038/s41467-021-26544-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 10/08/2021] [Indexed: 11/10/2022] Open
Abstract
Perception results from the interplay of sensory input and prior knowledge. Despite behavioral evidence that long-term priors powerfully shape perception, the neural mechanisms underlying these interactions remain poorly understood. We obtained direct cortical recordings in neurosurgical patients as they viewed ambiguous images that elicit constant perceptual switching. We observe top-down influences from the temporal to occipital cortex, during the preferred percept that is congruent with the long-term prior. By contrast, stronger feedforward drive is observed during the non-preferred percept, consistent with a prediction error signal. A computational model based on hierarchical predictive coding and attractor networks reproduces all key experimental findings. These results suggest a pattern of large-scale information flow change underlying long-term priors' influence on perception and provide constraints on theories about long-term priors' influence on perception.
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Affiliation(s)
- Richard Hardstone
- Neuroscience Institute, New York University Grossman School of Medicine, New York, NY, 10016, USA
| | - Michael Zhu
- Neuroscience Institute, New York University Grossman School of Medicine, New York, NY, 10016, USA
| | - Adeen Flinker
- Department of Neurology, New York University Grossman School of Medicine, New York, NY, 10016, USA
| | - Lucia Melloni
- Department of Neurology, New York University Grossman School of Medicine, New York, NY, 10016, USA
| | - Sasha Devore
- Department of Neurology, New York University Grossman School of Medicine, New York, NY, 10016, USA
| | - Daniel Friedman
- Department of Neurology, New York University Grossman School of Medicine, New York, NY, 10016, USA
| | - Patricia Dugan
- Department of Neurology, New York University Grossman School of Medicine, New York, NY, 10016, USA
| | - Werner K Doyle
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, NY, 10016, USA
| | - Orrin Devinsky
- Department of Neurology, New York University Grossman School of Medicine, New York, NY, 10016, USA
| | - Biyu J He
- Neuroscience Institute, New York University Grossman School of Medicine, New York, NY, 10016, USA.
- Department of Neurology, New York University Grossman School of Medicine, New York, NY, 10016, USA.
- Department of Neuroscience and Physiology, New York University Grossman School of Medicine, New York, NY, 10016, USA.
- Department of Radiology, New York University Grossman School of Medicine, New York, NY, 10016, USA.
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6
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Moran AK, Eiting TP, Wachowiak M. Circuit Contributions to Sensory-Driven Glutamatergic Drive of Olfactory Bulb Mitral and Tufted Cells During Odorant Inhalation. Front Neural Circuits 2021; 15:779056. [PMID: 34776878 PMCID: PMC8578712 DOI: 10.3389/fncir.2021.779056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 10/06/2021] [Indexed: 11/20/2022] Open
Abstract
In the mammalian olfactory bulb (OB), mitral/tufted (MT) cells respond to odorant inhalation with diverse temporal patterns that are thought to encode odor information. Much of this diversity is already apparent at the level of glutamatergic input to MT cells, which receive direct, monosynaptic excitatory input from olfactory sensory neurons (OSNs) as well as a multisynaptic excitatory drive via glutamatergic interneurons. Both pathways are also subject to modulation by inhibitory circuits in the glomerular layer of the OB. To understand the role of direct OSN input vs. postsynaptic OB circuit mechanisms in shaping diverse dynamics of glutamatergic drive to MT cells, we imaged glutamate signaling onto MT cell dendrites in anesthetized mice while blocking multisynaptic excitatory drive with ionotropic glutamate receptor antagonists and blocking presynaptic modulation of glutamate release from OSNs with GABAB receptor antagonists. GABAB receptor blockade increased the magnitude of inhalation-linked glutamate transients onto MT cell apical dendrites without altering their inhalation-linked dynamics, confirming that presynaptic inhibition impacts the gain of OSN inputs to the OB. Surprisingly, blockade of multisynaptic excitation only modestly impacted glutamatergic input to MT cells, causing a slight reduction in the amplitude of inhalation-linked glutamate transients in response to low odorant concentrations and no change in the dynamics of each transient. The postsynaptic blockade also modestly impacted glutamate dynamics over a slower timescale, mainly by reducing adaptation of the glutamate response across multiple inhalations of odorant. These results suggest that direct glutamatergic input from OSNs provides the bulk of excitatory drive to MT cells, and that diversity in the dynamics of this input may be a primary determinant of the temporal diversity in MT cell responses that underlies odor representations at this stage.
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Affiliation(s)
- Andrew K. Moran
- Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, UT, United States
- Department of Neurobiology, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Thomas P. Eiting
- Department of Neurobiology, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Matt Wachowiak
- Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, UT, United States
- Department of Neurobiology, University of Utah School of Medicine, Salt Lake City, UT, United States
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7
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The human olfactory bulb processes odor valence representation and cues motor avoidance behavior. Proc Natl Acad Sci U S A 2021; 118:2101209118. [PMID: 34645711 PMCID: PMC8545486 DOI: 10.1073/pnas.2101209118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/21/2021] [Indexed: 11/18/2022] Open
Abstract
Determining the valence of an odor to guide rapid approach-avoidance behavior is thought to be one of the core tasks of the olfactory system, and yet little is known of the initial neural mechanisms supporting this process or of its subsequent behavioral manifestation in humans. In two experiments, we measured the functional processing of odor valence perception in the human olfactory bulb (OB)-the first processing stage of the olfactory system-using a noninvasive method as well as assessed the subsequent motor avoidance response. We demonstrate that odor valence perception is associated with both gamma and beta activity in the human OB. Moreover, we show that negative, but not positive, odors initiate an early beta response in the OB, a response that is linked to a preparatory neural motor response in the motor cortex. Finally, in a separate experiment, we show that negative odors trigger a full-body motor avoidance response, manifested as a rapid leaning away from the odor, within the time period predicted by the OB results. Taken together, these results demonstrate that the human OB processes odor valence in a sequential manner in both the gamma and beta frequency bands and suggest that rapid processing of unpleasant odors in the OB might underlie rapid approach-avoidance decisions.
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8
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Martelli C, Storace DA. Stimulus Driven Functional Transformations in the Early Olfactory System. Front Cell Neurosci 2021; 15:684742. [PMID: 34413724 PMCID: PMC8369031 DOI: 10.3389/fncel.2021.684742] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 07/06/2021] [Indexed: 11/17/2022] Open
Abstract
Olfactory stimuli are encountered across a wide range of odor concentrations in natural environments. Defining the neural computations that support concentration invariant odor perception, odor discrimination, and odor-background segmentation across a wide range of stimulus intensities remains an open question in the field. In principle, adaptation could allow the olfactory system to adjust sensory representations to the current stimulus conditions, a well-known process in other sensory systems. However, surprisingly little is known about how adaptation changes olfactory representations and affects perception. Here we review the current understanding of how adaptation impacts processing in the first two stages of the vertebrate olfactory system, olfactory receptor neurons (ORNs), and mitral/tufted cells.
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Affiliation(s)
- Carlotta Martelli
- Institute of Developmental Biology and Neurobiology, University of Mainz, Mainz, Germany
| | - Douglas Anthony Storace
- Department of Biological Science, Florida State University, Tallahassee, FL, United States
- Program in Neuroscience, Florida State University, Tallahassee, FL, United States
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9
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Levinson M, Podvalny E, Baete SH, He BJ. Cortical and subcortical signatures of conscious object recognition. Nat Commun 2021; 12:2930. [PMID: 34006884 PMCID: PMC8131711 DOI: 10.1038/s41467-021-23266-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 04/12/2021] [Indexed: 11/29/2022] Open
Abstract
The neural mechanisms underlying conscious recognition remain unclear, particularly the roles played by the prefrontal cortex, deactivated brain areas and subcortical regions. We investigated neural activity during conscious object recognition using 7 Tesla fMRI while human participants viewed object images presented at liminal contrasts. Here, we show both recognized and unrecognized images recruit widely distributed cortical and subcortical regions; however, recognized images elicit enhanced activation of visual, frontoparietal, and subcortical networks and stronger deactivation of the default-mode network. For recognized images, object category information can be decoded from all of the involved cortical networks but not from subcortical regions. Phase-scrambled images trigger strong involvement of inferior frontal junction, anterior cingulate cortex and default-mode network, implicating these regions in inferential processing under increased uncertainty. Our results indicate that content-specific activity in both activated and deactivated cortical networks and non-content-specific subcortical activity support conscious recognition. Cortical and subcortical neural activity supporting conscious object recognition has not yet been well defined. Here, the authors describe these networks and show recognition-related category information can be decoded from widespread cortical activity but not subcortical activity.
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Affiliation(s)
- Max Levinson
- Neuroscience Institute, New York University School of Medicine, New York, NY, USA
| | - Ella Podvalny
- Neuroscience Institute, New York University School of Medicine, New York, NY, USA
| | - Steven H Baete
- Department of Radiology, New York University School of Medicine, New York, NY, USA
| | - Biyu J He
- Neuroscience Institute, New York University School of Medicine, New York, NY, USA. .,Department of Radiology, New York University School of Medicine, New York, NY, USA. .,Department of Neurology, New York University School of Medicine, New York, NY, USA. .,Department of Neuroscience & Physiology, New York University School of Medicine, New York, NY, USA.
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10
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Findley TM, Wyrick DG, Cramer JL, Brown MA, Holcomb B, Attey R, Yeh D, Monasevitch E, Nouboussi N, Cullen I, Songco JO, King JF, Ahmadian Y, Smear MC. Sniff-synchronized, gradient-guided olfactory search by freely moving mice. eLife 2021; 10:e58523. [PMID: 33942713 PMCID: PMC8169121 DOI: 10.7554/elife.58523] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Accepted: 04/22/2021] [Indexed: 01/18/2023] Open
Abstract
For many organisms, searching for relevant targets such as food or mates entails active, strategic sampling of the environment. Finding odorous targets may be the most ancient search problem that motile organisms evolved to solve. While chemosensory navigation has been well characterized in microorganisms and invertebrates, spatial olfaction in vertebrates is poorly understood. We have established an olfactory search assay in which freely moving mice navigate noisy concentration gradients of airborne odor. Mice solve this task using concentration gradient cues and do not require stereo olfaction for performance. During task performance, respiration and nose movement are synchronized with tens of milliseconds precision. This synchrony is present during trials and largely absent during inter-trial intervals, suggesting that sniff-synchronized nose movement is a strategic behavioral state rather than simply a constant accompaniment to fast breathing. To reveal the spatiotemporal structure of these active sensing movements, we used machine learning methods to parse motion trajectories into elementary movement motifs. Motifs fall into two clusters, which correspond to investigation and approach states. Investigation motifs lock precisely to sniffing, such that the individual motifs preferentially occur at specific phases of the sniff cycle. The allocentric structure of investigation and approach indicates an advantage to sampling both sides of the sharpest part of the odor gradient, consistent with a serial-sniff strategy for gradient sensing. This work clarifies sensorimotor strategies for mouse olfactory search and guides ongoing work into the underlying neural mechanisms.
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Affiliation(s)
- Teresa M Findley
- Department of Biology and Institute of Neuroscience, University of OregonEugeneUnited States
| | - David G Wyrick
- Department of Biology and Institute of Neuroscience, University of OregonEugeneUnited States
| | - Jennifer L Cramer
- Department of Psychology and Institute of Neuroscience, University of OregonEugeneUnited States
| | - Morgan A Brown
- Department of Psychology and Institute of Neuroscience, University of OregonEugeneUnited States
| | - Blake Holcomb
- Department of Psychology and Institute of Neuroscience, University of OregonEugeneUnited States
| | - Robin Attey
- Department of Psychology and Institute of Neuroscience, University of OregonEugeneUnited States
| | - Dorian Yeh
- Department of Psychology and Institute of Neuroscience, University of OregonEugeneUnited States
| | - Eric Monasevitch
- Department of Psychology and Institute of Neuroscience, University of OregonEugeneUnited States
| | - Nelly Nouboussi
- Department of Psychology and Institute of Neuroscience, University of OregonEugeneUnited States
| | - Isabelle Cullen
- Department of Psychology and Institute of Neuroscience, University of OregonEugeneUnited States
| | - Jeremea O Songco
- Department of Biology and Institute of Neuroscience, University of OregonEugeneUnited States
| | - Jared F King
- Department of Psychology and Institute of Neuroscience, University of OregonEugeneUnited States
| | - Yashar Ahmadian
- Department of Biology and Institute of Neuroscience, University of OregonEugeneUnited States
- Computational & Biological Learning Lab, University of CambridgeCambridgeUnited Kingdom
| | - Matthew C Smear
- Department of Psychology and Institute of Neuroscience, University of OregonEugeneUnited States
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11
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Dynamics of Glutamatergic Drive Underlie Diverse Responses of Olfactory Bulb Outputs In Vivo. eNeuro 2021; 8:ENEURO.0110-21.2021. [PMID: 33795414 PMCID: PMC8059884 DOI: 10.1523/eneuro.0110-21.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 03/19/2021] [Indexed: 11/24/2022] Open
Abstract
Mitral/tufted (MT) cells of the olfactory bulb (OB) show diverse temporal responses to odorant stimulation that are thought to encode odor information. Much of this diversity is thought to arise from inhibitory OB circuits, but the dynamics of excitatory input to MT cells, which is driven in a feedforward manner by sensory afferents, may also be important. To examine the contribution of excitatory input dynamics to generating temporal diversity in MT cells, we imaged glutamate signaling onto MT cell dendrites in anesthetized and awake mice. We found surprising diversity in the temporal dynamics of these signals. Inhalation-linked glutamate transients were variable in onset latency and duration, and in awake mice the degree of coupling to inhalation varied substantially with odorant identity and concentration. Successive inhalations of odorant produced nonlinear changes in glutamate signaling that included facilitating, adapting and suppressive responses and which varied with odorant identity and concentration. Dual-color imaging of glutamate and calcium signals from MT cells in the same glomerulus revealed highly correlated presynaptic and postsynaptic signals across these different response types. Suppressive calcium responses in MT cells were nearly always accompanied by suppression in the glutamate signal, providing little evidence for MT cell suppression by lateral or feedforward inhibition. These results indicate a high degree of diversity in the dynamics of excitatory input to MT cells, and suggest that these dynamics may account for much of the diversity in MT cell responses that underlies OB odor representations.
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12
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Kudryavitskaya E, Marom E, Shani-Narkiss H, Pash D, Mizrahi A. Flexible categorization in the mouse olfactory bulb. Curr Biol 2021; 31:1616-1631.e4. [DOI: 10.1016/j.cub.2021.01.063] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Revised: 12/11/2020] [Accepted: 01/19/2021] [Indexed: 11/30/2022]
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13
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Losacco J, George NM, Hiratani N, Restrepo D. The Olfactory Bulb Facilitates Use of Category Bounds for Classification of Odorants in Different Intensity Groups. Front Cell Neurosci 2020; 14:613635. [PMID: 33362477 PMCID: PMC7759615 DOI: 10.3389/fncel.2020.613635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 11/16/2020] [Indexed: 11/22/2022] Open
Abstract
Signal processing of odor inputs to the olfactory bulb (OB) changes through top-down modulation whose shaping of neural rhythms in response to changes in stimulus intensity is not understood. Here we asked whether the representation of a high vs. low intensity odorant in the OB by oscillatory neural activity changed as the animal learned to discriminate odorant concentration ranges in a go-no go task. We trained mice to discriminate between high vs. low concentration odorants by learning to lick to the rewarded group (low or high). We recorded the local field potential (LFP) in the OB of these mice and calculated the theta-referenced beta or gamma oscillation power (theta phase-referenced power, or tPRP). We found that as the mouse learned to differentiate odorant concentrations, tPRP diverged between trials for the rewarded vs. the unrewarded concentration range. For the proficient animal, linear discriminant analysis was able to predict the rewarded odorant group and the performance of this classifier correlated with the percent correct behavior in the odor concentration discrimination task. Interestingly, the behavioral response and decoding accuracy were asymmetric as a function of concentration when the rewarded stimulus was shifted between the high and low odorant concentration ranges. A model for decision making motivated by the statistics of OB activity that uses a single threshold in a logarithmic concentration scale displays this asymmetry. Taken together with previous studies on the intensity criteria for decisions on odorant concentrations, our finding suggests that OB oscillatory events facilitate decision making to classify concentrations using a single intensity criterion.
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Affiliation(s)
- Justin Losacco
- Neuroscience Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Nicholas M. George
- Neuroscience Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Naoki Hiratani
- Gatsby Computational Neuroscience Unit, University College London, London, United Kingdom
| | - Diego Restrepo
- Neuroscience Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
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14
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Abstract
In mammals, odor information detected by olfactory sensory neurons is converted to a topographic map of activated glomeruli in the olfactory bulb. Mitral cells and tufted cells transmit signals sequentially to the olfactory cortex for behavioral outputs. To elicit innate behavioral responses, odor signals are directly transmitted by distinct subsets of mitral cells from particular functional domains in the olfactory bulb to specific amygdala nuclei. As for the learned decisions, input signals are conveyed by tufted cells as well as by mitral cells to the olfactory cortex. Behavioral scene cells link the odor information to the valence cells in the amygdala to elicit memory-based behavioral responses. Olfactory decision and perception take place in relation to the respiratory cycle. How is the sensory quality imposed on the olfactory inputs for behavioral outputs? How are the two types of odor signals, innate and learned, processed during respiration? Here, we review recent progress on the study of neural circuits involved in decision making in the mouse olfactory system.
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Affiliation(s)
- Kensaku Mori
- RIKEN Center for Brain Science, Wako, Saitama, 351-0198, Japan;
| | - Hitoshi Sakano
- Department of Brain Function, School of Medical Sciences, University of Fukui, Matsuoka, Fukui 910-1197, Japan;
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15
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Ona Jodar T, Lage-Rupprecht V, Abraham NM, Rose CR, Egger V. Local Postsynaptic Signaling on Slow Time Scales in Reciprocal Olfactory Bulb Granule Cell Spines Matches Asynchronous Release. Front Synaptic Neurosci 2020; 12:551691. [PMID: 33304264 PMCID: PMC7701096 DOI: 10.3389/fnsyn.2020.551691] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 10/19/2020] [Indexed: 11/13/2022] Open
Abstract
In the vertebrate olfactory bulb (OB), axonless granule cells (GC) mediate self- and lateral inhibitory interactions between mitral/tufted cells via reciprocal dendrodendritic synapses. Locally triggered release of GABA from the large reciprocal GC spines occurs on both fast and slow time scales, possibly enabling parallel processing during olfactory perception. Here we investigate local mechanisms for asynchronous spine output. To reveal the temporal and spatial characteristics of postsynaptic ion transients, we imaged spine and adjacent dendrite Ca2 +- and Na+-signals with minimal exogenous buffering by the respective fluorescent indicator dyes upon two-photon uncaging of DNI-glutamate in OB slices from juvenile rats. Both postsynaptic fluorescence signals decayed slowly, with average half durations in the spine head of t1 / 2_Δ[Ca2 +]i ∼500 ms and t1 / 2_Δ[Na+]i ∼1,000 ms. We also analyzed the kinetics of already existing data of postsynaptic spine Ca2 +-signals in response to glomerular stimulation in OB slices from adult mice, either WT or animals with partial GC glutamate receptor deletions (NMDAR: GluN1 subunit; AMPAR: GluA2 subunit). In a large subset of spines the fluorescence signal had a protracted rise time (average time to peak ∼400 ms, range 20 to >1,000 ms). This slow rise was independent of Ca2 + entry via NMDARs, since similarly slow signals occurred in ΔGluN1 GCs. Additional Ca2 + entry in ΔGluA2 GCs (with AMPARs rendered Ca2 +-permeable), however, resulted in larger ΔF/Fs that rose yet more slowly. Thus GC spines appear to dispose of several local mechanisms to promote asynchronous GABA release, which are reflected in the time course of mitral/tufted cell recurrent inhibition.
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Affiliation(s)
- Tiffany Ona Jodar
- Regensburg University, Regensburg, Germany
- Institut D’Investigacions Biomèdiques, Barcelona, Spain
| | - Vanessa Lage-Rupprecht
- Regensburg University, Regensburg, Germany
- Fraunhofer Institute for Algorithms and Scientific Computing, St. Augustin, Germany
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16
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Bhattacharjee AS, Konakamchi S, Turaev D, Vincis R, Nunes D, Dingankar AA, Spors H, Carleton A, Kuner T, Abraham NM. Similarity and Strength of Glomerular Odor Representations Define a Neural Metric of Sniff-Invariant Discrimination Time. Cell Rep 2020; 28:2966-2978.e5. [PMID: 31509755 PMCID: PMC7115995 DOI: 10.1016/j.celrep.2019.08.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 05/14/2019] [Accepted: 07/31/2019] [Indexed: 12/01/2022] Open
Abstract
The olfactory environment is first represented by glomerular activity patterns in the olfactory bulb. It remains unclear how these representations intersect with sampling behavior to account for the time required to discriminate odors. Using different chemical classes, we investigate glomerular representations and sniffing behavior during olfactory decision-making. Mice rapidly discriminate odorants and learn to increase sniffing frequency at a fixed latency after trial initiation, independent of odor identity. Relative to the increase in sniffing frequency, monomolecular odorants are discriminated within 10-40 ms, while binary mixtures require an additional 60-70 ms. Intrinsic imaging of glomerular activity in anesthetized and awake mice reveals that Euclidean distance between activity patterns and the time needed for discriminations are anti-correlated. Therefore, the similarity of glomerular patterns and their activation strengths, rather than sampling behavior, define the extent of neuronal processing required for odor discrimination, establishing a neural metric to predict olfactory discrimination time.
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Affiliation(s)
| | - Sasank Konakamchi
- Indian Institute of Science Education and Research (IISER), Pune, Maharashtra 411008, India
| | - Dmitrij Turaev
- WIN Olfactory Dynamics Group, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany; Department of Molecular Neurogenetics, Max-Planck-Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
| | - Roberto Vincis
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Genève 4, Switzerland
| | - Daniel Nunes
- Institute of Anatomy and Cell Biology, Heidelberg University, INF 307, 69120 Heidelberg, Germany
| | - Atharva A Dingankar
- Indian Institute of Science Education and Research (IISER), Pune, Maharashtra 411008, India
| | - Hartwig Spors
- WIN Olfactory Dynamics Group, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany; Department of Molecular Neurogenetics, Max-Planck-Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
| | - Alan Carleton
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Genève 4, Switzerland
| | - Thomas Kuner
- Institute of Anatomy and Cell Biology, Heidelberg University, INF 307, 69120 Heidelberg, Germany; WIN Olfactory Dynamics Group, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany
| | - Nixon M Abraham
- Indian Institute of Science Education and Research (IISER), Pune, Maharashtra 411008, India; Institute of Anatomy and Cell Biology, Heidelberg University, INF 307, 69120 Heidelberg, Germany; WIN Olfactory Dynamics Group, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany; Department of Basic Neurosciences, School of Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Genève 4, Switzerland.
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17
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Malvaut S, Constantinescu VS, Dehez H, Doric S, Saghatelyan A. Deciphering Brain Function by Miniaturized Fluorescence Microscopy in Freely Behaving Animals. Front Neurosci 2020; 14:819. [PMID: 32848576 PMCID: PMC7432153 DOI: 10.3389/fnins.2020.00819] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 07/14/2020] [Indexed: 11/19/2022] Open
Abstract
Animal behavior is regulated by environmental stimuli and is shaped by the activity of neural networks, underscoring the importance of assessing the morpho-functional properties of different populations of cells in freely behaving animals. In recent years, a number of optical tools have been developed to monitor and modulate neuronal and glial activity at the protein, cellular, or network level and have opened up new avenues for studying brain function in freely behaving animals. Tools such as genetically encoded sensors and actuators are now commonly used for studying brain activity and function through their expression in different neuronal ensembles. In parallel, microscopy has also made major progress over the last decades. The advent of miniature microscopes (mini-microscopes also called mini-endoscopes) has become a method of choice for studying brain activity at the cellular and network levels in different brain regions of freely behaving mice. This technique also allows for longitudinal investigations while animals carrying the microscope on their head are performing behavioral tasks. In this review, we will discuss mini-endoscopic imaging and the advantages that these devices offer to research. We will also discuss current limitations of and potential future improvements in mini-endoscopic imaging.
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Affiliation(s)
- Sarah Malvaut
- CERVO Brain Research Center, Quebec City, QC, Canada
- Department of Psychiatry and Neuroscience, Universite Laval, Quebec City, QC, Canada
| | - Vlad-Stefan Constantinescu
- CERVO Brain Research Center, Quebec City, QC, Canada
- Department of Psychiatry and Neuroscience, Universite Laval, Quebec City, QC, Canada
| | | | - Sead Doric
- Doric Lenses Inc., Quebec City, QC, Canada
| | - Armen Saghatelyan
- CERVO Brain Research Center, Quebec City, QC, Canada
- Department of Psychiatry and Neuroscience, Universite Laval, Quebec City, QC, Canada
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18
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Differential Impacts of Repeated Sampling on Odor Representations by Genetically-Defined Mitral and Tufted Cell Subpopulations in the Mouse Olfactory Bulb. J Neurosci 2020; 40:6177-6188. [PMID: 32601245 DOI: 10.1523/jneurosci.0258-20.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 06/16/2020] [Accepted: 06/18/2020] [Indexed: 12/20/2022] Open
Abstract
Sniffing, the active control of breathing beyond passive respiration, is used by mammals to modulate olfactory sampling. Sniffing allows animals to make odor-guided decisions within ∼200 ms, but animals routinely engage in bouts of high-frequency sniffing spanning several seconds; the impact of such repeated odorant sampling on odor representations remains unclear. We investigated this question in the mouse olfactory bulb (OB), where mitral and tufted cells (MTCs) form parallel output streams of odor information processing. To test the impact of repeated odorant sampling on MTC responses, we used two-photon imaging in anesthetized male and female mice to record activation of MTCs while precisely varying inhalation frequency. A combination of genetic targeting and viral expression of GCaMP6 reporters allowed us to access mitral cell (MC) and superficial tufted cell (sTC) subpopulations separately. We found that repeated odorant sampling differentially affected responses in MCs and sTCs, with MCs showing more diversity than sTCs over the same time period. Impacts of repeated sampling among MCs included both increases and decreases in excitation, as well as changes in response polarity. Response patterns across simultaneously-imaged MCs reformatted over time, with representations of different odorants becoming more distinct. Individual MCs responded differentially to changes in inhalation frequency, whereas sTC responses were more uniform over time and across frequency. Our results support the idea that MCs and TCs comprise functionally distinct pathways for odor information processing, and suggest that the reformatting of MC odor representations by high-frequency sniffing may serve to enhance the discrimination of similar odors.SIGNIFICANCE STATEMENT Repeated sampling of odorants during high-frequency respiration (sniffing) is a hallmark of active odorant sampling by mammals; however, the adaptive function of this behavior remains unclear. We found distinct effects of repeated sampling on odor representations carried by the two main output channels from the mouse olfactory bulb (OB), mitral and tufted cells (MTCs). Mitral cells (MCs) showed more diverse changes in response patterns over time as compared with tufted cells (TCs), leading to odorant representations that were more distinct after repeated sampling. These results support the idea that MTCs contribute different aspects to encoding odor information, and they indicate that MCs (but not TCs) may play a primary role in the modulation of olfactory processing by sampling behavior.
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19
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Dalal T, Gupta N, Haddad R. Bilateral and unilateral odor processing and odor perception. Commun Biol 2020; 3:150. [PMID: 32238904 PMCID: PMC7113286 DOI: 10.1038/s42003-020-0876-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 03/05/2020] [Indexed: 11/09/2022] Open
Abstract
Imagine smelling a novel perfume with only one nostril and then smelling it again with the other nostril. Clearly, you can tell that it is the same perfume both times. This simple experiment demonstrates that odor information is shared across both hemispheres to enable perceptual unity. In many sensory systems, perceptual unity is believed to be mediated by inter-hemispheric connections between iso-functional cortical regions. However, in the olfactory system, the underlying neural mechanisms that enable this coordination are unclear because the two olfactory cortices are not topographically organized and do not seem to have homotypic inter-hemispheric mapping. This review presents recent advances in determining which aspects of odor information are processed unilaterally or bilaterally, and how odor information is shared across the two hemispheres. We argue that understanding the mechanisms of inter-hemispheric coordination can provide valuable insights that are hard to achieve when focusing on one hemisphere alone.
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Affiliation(s)
- Tal Dalal
- The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, 5290002, Israel
| | - Nitin Gupta
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, 208016, India
| | - Rafi Haddad
- The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, 5290002, Israel.
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20
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Task-Demand-Dependent Neural Representation of Odor Information in the Olfactory Bulb and Posterior Piriform Cortex. J Neurosci 2019; 39:10002-10018. [PMID: 31672791 DOI: 10.1523/jneurosci.1234-19.2019] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 10/16/2019] [Accepted: 10/19/2019] [Indexed: 02/03/2023] Open
Abstract
In awake rodents, the neural representation of olfactory information in the olfactory bulb is largely dependent on brain state and behavioral context. Learning-modified neural plasticity has been observed in mitral/tufted cells, the main output neurons of the olfactory bulb. Here, we propose that the odor information encoded by mitral/tufted cell responses in awake mice is highly dependent on the behavioral task demands. We used fiber photometry to record calcium signals from the mitral/tufted cell population in awake, head-fixed male mice under different task demands. We found that the mitral/tufted cell population showed similar responses to two distinct odors when the odors were presented in the context of a go/go task, in which the mice received a water reward regardless of the identity of the odor presented. However, when the same odors were presented in a go/no-go task, in which one odor was rewarded and the other was not, then the mitral cell population responded very differently to the two odors, characterized by a robust reduction in the response to the nonrewarded odor. Thus, the representation of odors in the mitral/tufted cell population depends on whether the task requires discrimination of the odors. Strikingly, downstream of the olfactory bulb, pyramidal neurons in the posterior piriform cortex also displayed a task-demand-dependent neural representation of odors, but the anterior piriform cortex did not, indicating that these two important higher olfactory centers use different strategies for neural representation.SIGNIFICANCE STATEMENT The most important task of the olfactory system is to generate a precise representation of odor information under different brain states. Whether the representation of odors by neurons in olfactory centers such as the olfactory bulb and the piriform cortex depends on task demands remains elusive. We find that odor representation in the mitral/tufted cells of the olfactory bulb depends on whether the task requires odor discrimination. A similar neural representation is found in the posterior piriform cortex but not the anterior piriform cortex, indicating that these higher olfactory centers use different representational strategies. The task-demand-dependent representational strategy is likely important for facilitating information processing in higher brain centers responsible for decision making and encoding of salience.
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21
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In vivo neurovascular response to focused photoactivation of Channelrhodopsin-2. Neuroimage 2019; 192:135-144. [DOI: 10.1016/j.neuroimage.2019.01.036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 12/31/2018] [Accepted: 01/14/2019] [Indexed: 01/03/2023] Open
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22
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Restoring wild-type-like CA1 network dynamics and behavior during adulthood in a mouse model of schizophrenia. Nat Neurosci 2018; 21:1412-1420. [PMID: 30224804 DOI: 10.1038/s41593-018-0225-y] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 07/12/2018] [Indexed: 01/16/2023]
Abstract
Schizophrenia is a severely debilitating neurodevelopmental disorder. Establishing a causal link between circuit dysfunction and particular behavioral traits that are relevant to schizophrenia is crucial to shed new light on the mechanisms underlying the pathology. We studied an animal model of the human 22q11 deletion syndrome, the mutation that represents the highest genetic risk of developing schizophrenia. We observed a desynchronization of hippocampal neuronal assemblies that resulted from parvalbumin interneuron hypoexcitability. Rescuing parvalbumin interneuron excitability with pharmacological or chemogenetic approaches was sufficient to restore wild-type-like CA1 network dynamics and hippocampal-dependent behavior during adulthood. In conclusion, our data provide insights into the network dysfunction underlying schizophrenia and highlight the use of reverse engineering to restore physiological and behavioral phenotypes in an animal model of neurodevelopmental disorder.
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23
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Lüdke A, Raiser G, Nehrkorn J, Herz AVM, Galizia CG, Szyszka P. Calcium in Kenyon Cell Somata as a Substrate for an Olfactory Sensory Memory in Drosophila. Front Cell Neurosci 2018; 12:128. [PMID: 29867361 PMCID: PMC5960692 DOI: 10.3389/fncel.2018.00128] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 04/23/2018] [Indexed: 12/31/2022] Open
Abstract
Animals can form associations between temporally separated stimuli. To do so, the nervous system has to retain a neural representation of the first stimulus until the second stimulus appears. The neural substrate of such sensory stimulus memories is unknown. Here, we search for a sensory odor memory in the insect olfactory system and characterize odorant-evoked Ca2+ activity at three consecutive layers of the olfactory system in Drosophila: in olfactory receptor neurons (ORNs) and projection neurons (PNs) in the antennal lobe, and in Kenyon cells (KCs) in the mushroom body. We show that the post-stimulus responses in ORN axons, PN dendrites, PN somata, and KC dendrites are odor-specific, but they are not predictive of the chemical identity of past olfactory stimuli. However, the post-stimulus responses in KC somata carry information about the identity of previous olfactory stimuli. These findings show that the Ca2+ dynamics in KC somata could encode a sensory memory of odorant identity and thus might serve as a basis for associations between temporally separated stimuli.
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Affiliation(s)
- Alja Lüdke
- Department of Biology, Neurobiology, University of Konstanz, Konstanz, Germany
| | - Georg Raiser
- Department of Biology, Neurobiology, University of Konstanz, Konstanz, Germany
- International Max Planck Research School for Organismal Biology, Konstanz, Germany
| | - Johannes Nehrkorn
- Fakultät für Biologie, Ludwig-Maximilians-Universität München, Martinsried, Germany
- Bernstein Center for Computational Neuroscience, Munich, Germany
| | - Andreas V. M. Herz
- Fakultät für Biologie, Ludwig-Maximilians-Universität München, Martinsried, Germany
- Bernstein Center for Computational Neuroscience, Munich, Germany
| | - C. Giovanni Galizia
- Department of Biology, Neurobiology, University of Konstanz, Konstanz, Germany
| | - Paul Szyszka
- Department of Biology, Neurobiology, University of Konstanz, Konstanz, Germany
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24
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Guo Y, Wolff FE, Schapiro I, Elstner M, Marazzi M. Different hydrogen bonding environments of the retinal protonated Schiff base control the photoisomerization in channelrhodopsin-2. Phys Chem Chem Phys 2018; 20:27501-27509. [DOI: 10.1039/c8cp05210g] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The first event of the channelrhodopsin-2 (ChR2) photocycle, i.e. trans-to-cis photoisomerization, is studied by means of quantum mechanics/molecular mechanics, taking into account the flexible retinal environment in the ground state.
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Affiliation(s)
- Yanan Guo
- Department of Theoretical Chemical Biology
- Institute of Physical Chemistry
- Karlsruhe Institute of Technology
- 76131 Karlsruhe
- Germany
| | - Franziska E. Wolff
- Department of Theoretical Chemical Biology
- Institute of Physical Chemistry
- Karlsruhe Institute of Technology
- 76131 Karlsruhe
- Germany
| | - Igor Schapiro
- Fritz Haber Center for Molecular Dynamics Research
- Institute of Chemistry
- Hebrew University of Jerusalem
- Jerusalem
- Israel
| | - Marcus Elstner
- Department of Theoretical Chemical Biology
- Institute of Physical Chemistry
- Karlsruhe Institute of Technology
- 76131 Karlsruhe
- Germany
| | - Marco Marazzi
- Department of Theoretical Chemical Biology
- Institute of Physical Chemistry
- Karlsruhe Institute of Technology
- 76131 Karlsruhe
- Germany
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25
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Gillary G, Heydt RVD, Niebur E. Short-term depression and transient memory in sensory cortex. J Comput Neurosci 2017; 43:273-294. [PMID: 29027605 PMCID: PMC6022432 DOI: 10.1007/s10827-017-0662-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 08/30/2017] [Accepted: 09/21/2017] [Indexed: 10/18/2022]
Abstract
Persistent neuronal activity is usually studied in the context of short-term memory localized in central cortical areas. Recent studies show that early sensory areas also can have persistent representations of stimuli which emerge quickly (over tens of milliseconds) and decay slowly (over seconds). Traditional positive feedback models cannot explain sensory persistence for at least two reasons: (i) They show attractor dynamics, with transient perturbations resulting in a quasi-permanent change of system state, whereas sensory systems return to the original state after a transient. (ii) As we show, those positive feedback models which decay to baseline lose their persistence when their recurrent connections are subject to short-term depression, a common property of excitatory connections in early sensory areas. Dual time constant network behavior has also been implemented by nonlinear afferents producing a large transient input followed by much smaller steady state input. We show that such networks require unphysiologically large onset transients to produce the rise and decay observed in sensory areas. Our study explores how memory and persistence can be implemented in another model class, derivative feedback networks. We show that these networks can operate with two vastly different time courses, changing their state quickly when new information is coming in but retaining it for a long time, and that these capabilities are robust to short-term depression. Specifically, derivative feedback networks with short-term depression that acts differentially on positive and negative feedback projections are capable of dynamically changing their time constant, thus allowing fast onset and slow decay of responses without requiring unrealistically large input transients.
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Affiliation(s)
- Grant Gillary
- Zanvyl Krieger Mind/Brain Institute and Solomon Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Rüdiger von der Heydt
- Zanvyl Krieger Mind/Brain Institute and Solomon Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Ernst Niebur
- Zanvyl Krieger Mind/Brain Institute and Solomon Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD, 21218, USA.
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26
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History-Dependent Odor Processing in the Mouse Olfactory Bulb. J Neurosci 2017; 37:12018-12030. [PMID: 29109236 PMCID: PMC5719977 DOI: 10.1523/jneurosci.0755-17.2017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2017] [Revised: 09/15/2017] [Accepted: 10/22/2017] [Indexed: 12/02/2022] Open
Abstract
In nature, animals normally perceive sensory information on top of backgrounds. Thus, the neural substrate to perceive under background conditions is inherent in all sensory systems. Where and how sensory systems process backgrounds is not fully understood. In olfaction, just a few studies have addressed the issue of odor coding on top of continuous odorous backgrounds. Here, we tested how background odors are encoded by mitral cells (MCs) in the olfactory bulb (OB) of male mice. Using in vivo two-photon calcium imaging, we studied how MCs responded to odors in isolation versus their responses to the same odors on top of continuous backgrounds. We show that MCs adapt to continuous odor presentation and that mixture responses are different when preceded by background. In a subset of odor combinations, this history-dependent processing was useful in helping to identify target odors over background. Other odorous backgrounds were highly dominant such that target odors were completely masked by their presence. Our data are consistent in both low and high odor concentrations and in anesthetized and awake mice. Thus, odor processing in the OB is strongly influenced by the recent history of activity, which could have a powerful impact on how odors are perceived. SIGNIFICANCE STATEMENT We examined a basic feature of sensory processing in the olfactory bulb. Specifically, we measured how mitral cells adapt to continuous background odors and how target odors are encoded on top of such background. Our results show clear differences in odor coding based on the immediate history of the stimulus. Our results support the argument that odor coding in the olfactory bulb depends on the recent history of the sensory environment.
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27
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Yamada Y, Bhaukaurally K, Madarász TJ, Pouget A, Rodriguez I, Carleton A. Context- and Output Layer-Dependent Long-Term Ensemble Plasticity in a Sensory Circuit. Neuron 2017; 93:1198-1212.e5. [PMID: 28238548 PMCID: PMC5352733 DOI: 10.1016/j.neuron.2017.02.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 11/10/2016] [Accepted: 02/03/2017] [Indexed: 01/14/2023]
Abstract
Sensory information is translated into ensemble representations by various populations of projection neurons in brain circuits. The dynamics of ensemble representations formed by distinct channels of output neurons in diverse behavioral contexts remains largely unknown. We studied the two output neuron layers in the olfactory bulb (OB), mitral and tufted cells, using chronic two-photon calcium imaging in awake mice. Both output populations displayed similar odor response profiles. During passive sensory experience, both populations showed reorganization of ensemble odor representations yet stable pattern separation across days. Intriguingly, during active odor discrimination learning, mitral but not tufted cells exhibited improved pattern separation, although both populations showed reorganization of ensemble representations. An olfactory circuitry model suggests that cortical feedback on OB interneurons can trigger both forms of plasticity. In conclusion, we show that different OB output layers display unique context-dependent long-term ensemble plasticity, allowing parallel transfer of non-redundant sensory information to downstream centers. Video Abstract
Mitral and tufted cells in the olfactory bulb show similar odor-evoked responses Passive odor experience reorganizes ensemble odor representations in both cell types Associative odor learning specifically improves pattern separation in mitral cells Cortical feedback can trigger both forms of plasticity in a network model
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Affiliation(s)
- Yoshiyuki Yamada
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1 Rue Michel-Servet, 1211 Geneva 4, Switzerland; Geneva Neuroscience Center, University of Geneva, 1211 Geneva, Switzerland
| | - Khaleel Bhaukaurally
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1 Rue Michel-Servet, 1211 Geneva 4, Switzerland; Geneva Neuroscience Center, University of Geneva, 1211 Geneva, Switzerland
| | - Tamás J Madarász
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1 Rue Michel-Servet, 1211 Geneva 4, Switzerland; Geneva Neuroscience Center, University of Geneva, 1211 Geneva, Switzerland
| | - Alexandre Pouget
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1 Rue Michel-Servet, 1211 Geneva 4, Switzerland; Geneva Neuroscience Center, University of Geneva, 1211 Geneva, Switzerland; Gatsby Computational Neuroscience Unit, University College London, London, W1T 4JG, UK
| | - Ivan Rodriguez
- Geneva Neuroscience Center, University of Geneva, 1211 Geneva, Switzerland; Department of Genetics and Evolution, University of Geneva, 1211 Geneva, Switzerland.
| | - Alan Carleton
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1 Rue Michel-Servet, 1211 Geneva 4, Switzerland; Geneva Neuroscience Center, University of Geneva, 1211 Geneva, Switzerland.
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28
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Dense encoding of natural odorants by ensembles of sparsely activated neurons in the olfactory bulb. Sci Rep 2016; 6:36514. [PMID: 27824096 PMCID: PMC5099913 DOI: 10.1038/srep36514] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 10/18/2016] [Indexed: 11/09/2022] Open
Abstract
Sensory information undergoes substantial transformation along sensory pathways, usually encompassing sparsening of activity. In the olfactory bulb, though natural odorants evoke dense glomerular input maps, mitral and tufted (M/T) cells tuning is considered to be sparse because of highly odor-specific firing rate change. However, experiments used to draw this conclusion were either based on recordings performed in anesthetized preparations or used monomolecular odorants presented at arbitrary concentrations. In this study, we evaluated the lifetime and population sparseness evoked by natural odorants by capturing spike temporal patterning of neuronal assemblies instead of individual M/T tonic activity. Using functional imaging and tetrode recordings in awake mice, we show that natural odorants at their native concentrations are encoded by broad assemblies of M/T cells. While reducing odorant concentrations, we observed a reduced number of activated glomeruli representations and consequently a narrowing of M/T tuning curves. We conclude that natural odorants at their native concentrations recruit M/T cells with phasic rather than tonic activity. When encoding odorants in assemblies, M/T cells carry information about a vast number of odorants (lifetime sparseness). In addition, each natural odorant activates a broad M/T cell assembly (population sparseness).
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29
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Chang R, Baria AT, Flounders MW, He BJ. Unconsciously elicited perceptual prior. Neurosci Conscious 2016; 2016. [PMID: 27595010 DOI: 10.1093/nc/niw008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Increasing evidence over the past decade suggests that vision is not simply a passive, feed-forward process in which cortical areas relay progressively more abstract information to those higher up in the visual hierarchy, but rather an inferential process with top-down processes actively guiding and shaping perception. However, one major question that persists is whether such processes can be influenced by unconsciously perceived stimuli. Recent psychophysics and neuroimaging studies have revealed that while consciously perceived stimuli elicit stronger responses in higher visual and frontoparietal areas than those that fail to reach conscious awareness, the latter can still drive high-level brain and behavioral responses. We investigated whether unconscious processing of a masked natural image could facilitate subsequent conscious recognition of its degraded counterpart (a black-and-white "Mooney" image) presented many seconds later. We found that this is indeed the case, suggesting that conscious vision may be influenced by priors established by unconscious processing of a fleeting image.
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Affiliation(s)
- Raymond Chang
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA; Cornell University Weill Medical College, New York, NY 10065, USA
| | - Alexis T Baria
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA; Northwestern University Feinberg, School of Medicine, Chicago, IL 60611, USA
| | - Matthew W Flounders
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Biyu J He
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA; Departments of Neurology, Neuroscience and Physiology, and Radiology, Neuroscience Institute, New York University Langone Medical Center, NY 10016, USA
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Geramita MA, Burton SD, Urban NN. Distinct lateral inhibitory circuits drive parallel processing of sensory information in the mammalian olfactory bulb. eLife 2016; 5. [PMID: 27351103 PMCID: PMC4972542 DOI: 10.7554/elife.16039] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 06/27/2016] [Indexed: 11/13/2022] Open
Abstract
Splitting sensory information into parallel pathways is a common strategy in sensory systems. Yet, how circuits in these parallel pathways are composed to maintain or even enhance the encoding of specific stimulus features is poorly understood. Here, we have investigated the parallel pathways formed by mitral and tufted cells of the olfactory system in mice and characterized the emergence of feature selectivity in these cell types via distinct lateral inhibitory circuits. We find differences in activity-dependent lateral inhibition between mitral and tufted cells that likely reflect newly described differences in the activation of deep and superficial granule cells. Simulations show that these circuit-level differences allow mitral and tufted cells to best discriminate odors in separate concentration ranges, indicating that segregating information about different ranges of stimulus intensity may be an important function of these parallel sensory pathways. DOI:http://dx.doi.org/10.7554/eLife.16039.001 The brain often processes different features of sensory information in separate pathways. For example, when seeing an object, information about colour and movement are processed by separate types of neurons in the eye. These neurons in turn relay information to different sets of brain areas, all of which are active at the same time. Such parallel processing was originally not thought to apply to information about smell. This was because in mammals, the two types of neurons in the brain area that processes smell seemed to play the same role. However, more recent work suggests that there are in fact differences in the responses of these two neuron types (called mitral cells and tufted cells) to odors, suggesting that the brain might use parallel processing for information about smells too. Information travels along neurons in the form of electrical signals, and this activity is often seen in the form of a series of “spikes”. In a process called lateral inhibition, the activity of one neuron can feed back and inhibit the activity of its neighbors. This is important for enhancing contrast; in terms of the sense of smell, lateral inhibition is thought to help distinguish between similar odors. A technique called optogenetics allows the activity of particular neurons in an animal’s brain to be controlled by shining light onto them. Geramita et al. have now used this technique in mice to investigate whether there are differences in how lateral inhibition works in mitral cells and tufted cells. This revealed that lateral inhibition affects mitral cells only when they are spiking at intermediate firing rates, whereas tufted cells are only affected by lateral inhibition when spiking at low firing rates. Using computer simulations, Geramita et al. show that these different responses mean that mitral cells are best at distinguishing similar smells when they are present at high concentrations, while tufted cells are best at distinguishing similar smells that are present at low concentrations. These differences also mean that, by working together, mitral and tufted cells can distinguish between smells much better than either type of neuron on its own. These results demonstrate that, as with the other senses, the brain processes information about smell using parallel pathways. Future work is now needed to see what effect switching off the activity of either mitral or tufted cells will have on an animal’s behavior. DOI:http://dx.doi.org/10.7554/eLife.16039.002
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Affiliation(s)
- Matthew A Geramita
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, United States.,Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, United States
| | - Shawn D Burton
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, United States.,Center for the Neural Basis of Cognition, Carnegie Mellon University, Pittsburgh, United States
| | - Nathan N Urban
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, United States.,Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, United States
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31
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Grimaud J, Lledo PM. Illuminating odors: when optogenetics brings to light unexpected olfactory abilities. ACTA ACUST UNITED AC 2016; 23:249-54. [PMID: 27194792 PMCID: PMC4880145 DOI: 10.1101/lm.041269.115] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 03/17/2016] [Indexed: 11/25/2022]
Abstract
For hundreds of years, the sense of smell has generated great interest in the world literature, oenologists, and perfume makers but less of scientists. Only recently this sensory modality has gained new attraction in neuroscience when original tools issued from physiology, anatomy, or molecular biology were available to decipher how the brain makes sense of olfactory cues. However, this move was promptly dampened by the difficulties of developing quantitative approaches to study the relationship between the physical characteristics of stimuli and the sensations they create. An upswing of olfactory investigations occurred when genetic tools could be used in combination with devices borrowed from the physics of light (a hybrid technique called optogenetics) to scrutinize the olfactory system and to provide greater physiological precision for studying olfactory-driven behaviors. This review aims to present the most recent studies that have used light to activate components of the olfactory pathway, such as olfactory receptor neurons, or neurons located further downstream, while leaving intact others brain circuits. With the use of optogenetics to unravel the mystery of olfaction, scientists have begun to disentangle how the brain makes sense of smells. In this review, we shall discuss how the brain recognizes odors, how it memorizes them, and how animals make decisions based on odorants they are capable of sensing. Although this review deals with olfaction, the role of light will be central throughout.
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Affiliation(s)
- Julien Grimaud
- Institut Pasteur, Laboratory for Perception and Memory, F-75015 Paris, France Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 3571, F-75015 Paris, France
| | - Pierre-Marie Lledo
- Institut Pasteur, Laboratory for Perception and Memory, F-75015 Paris, France Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 3571, F-75015 Paris, France
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32
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Jercog P, Rogerson T, Schnitzer MJ. Large-Scale Fluorescence Calcium-Imaging Methods for Studies of Long-Term Memory in Behaving Mammals. Cold Spring Harb Perspect Biol 2016; 8:a021824. [PMID: 27048190 PMCID: PMC4852807 DOI: 10.1101/cshperspect.a021824] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
During long-term memory formation, cellular and molecular processes reshape how individual neurons respond to specific patterns of synaptic input. It remains poorly understood how such changes impact information processing across networks of mammalian neurons. To observe how networks encode, store, and retrieve information, neuroscientists must track the dynamics of large ensembles of individual cells in behaving animals, over timescales commensurate with long-term memory. Fluorescence Ca(2+)-imaging techniques can monitor hundreds of neurons in behaving mice, opening exciting avenues for studies of learning and memory at the network level. Genetically encoded Ca(2+) indicators allow neurons to be targeted by genetic type or connectivity. Chronic animal preparations permit repeated imaging of neural Ca(2+) dynamics over multiple weeks. Together, these capabilities should enable unprecedented analyses of how ensemble neural codes evolve throughout memory processing and provide new insights into how memories are organized in the brain.
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Affiliation(s)
- Pablo Jercog
- CNC Program, Stanford University, Stanford, California 94305
| | - Thomas Rogerson
- CNC Program, Stanford University, Stanford, California 94305
| | - Mark J Schnitzer
- CNC Program, Stanford University, Stanford, California 94305 Howard Hughes Medical Institute, Stanford University, Stanford, California 94305 James H. Clark Center for Biomedical Engineering & Sciences, Stanford University, Stanford, California 94305
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33
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Neural Coding of Perceived Odor Intensity. eNeuro 2015; 2:eN-NWR-0083-15. [PMID: 26665162 PMCID: PMC4672005 DOI: 10.1523/eneuro.0083-15.2015] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2015] [Revised: 10/25/2015] [Accepted: 10/28/2015] [Indexed: 01/02/2023] Open
Abstract
Stimulus intensity is a fundamental perceptual feature in all sensory systems. In olfaction, perceived odor intensity depends on at least two variables: odor concentration; and duration of the odor exposure or adaptation. To examine how neural activity at early stages of the olfactory system represents features relevant to intensity perception, we studied the responses of mitral/tufted cells (MTCs) while manipulating odor concentration and exposure duration. Temporal profiles of MTC responses to odors changed both as a function of concentration and with adaptation. However, despite the complexity of these responses, adaptation and concentration dependencies behaved similarly. These similarities were visualized by principal component analysis of average population responses and were quantified by discriminant analysis in a trial-by-trial manner. The qualitative functional dependencies of neuronal responses paralleled psychophysics results in humans. We suggest that temporal patterns of MTC responses in the olfactory bulb contribute to an internal perceptual variable: odor intensity.
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34
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Gschwend O, Abraham NM, Lagier S, Begnaud F, Rodriguez I, Carleton A. Neuronal pattern separation in the olfactory bulb improves odor discrimination learning. Nat Neurosci 2015; 18:1474-1482. [PMID: 26301325 PMCID: PMC4845880 DOI: 10.1038/nn.4089] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 06/23/2015] [Indexed: 12/15/2022]
Abstract
Neuronal pattern separation is thought to enable the brain to disambiguate sensory stimuli with overlapping features, thereby extracting valuable information. In the olfactory system, it remains unknown whether pattern separation acts as a driving force for sensory discrimination and the learning thereof. We found that overlapping odor-evoked input patterns to the mouse olfactory bulb (OB) were dynamically reformatted in the network on the timescale of a single breath, giving rise to separated patterns of activity in an ensemble of output neurons, mitral/tufted (M/T) cells. Notably, the extent of pattern separation in M/T assemblies predicted behavioral discrimination performance during the learning phase. Furthermore, exciting or inhibiting GABAergic OB interneurons, using optogenetics or pharmacogenetics, altered pattern separation and thereby odor discrimination learning in a bidirectional way. In conclusion, we propose that the OB network can act as a pattern separator facilitating olfactory stimulus distinction, a process that is sculpted by synaptic inhibition.
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Affiliation(s)
- Olivier Gschwend
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
- Geneva Neuroscience Center, University of Geneva, Switzerland
| | - Nixon M Abraham
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
- Geneva Neuroscience Center, University of Geneva, Switzerland
- Department of Genetics and Evolution, University of Geneva, 1211 Geneva, Switzerland
| | - Samuel Lagier
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
- Geneva Neuroscience Center, University of Geneva, Switzerland
| | - Frédéric Begnaud
- Firmenich SA, Corporate R&D Division / Analytical Innovation, route des Jeunes 1, CH-1211 Geneva 8, Switzerland
| | - Ivan Rodriguez
- Geneva Neuroscience Center, University of Geneva, Switzerland
- Department of Genetics and Evolution, University of Geneva, 1211 Geneva, Switzerland
| | - Alan Carleton
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
- Geneva Neuroscience Center, University of Geneva, Switzerland
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35
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Vincis R, Lagier S, Van De Ville D, Rodriguez I, Carleton A. Sensory-Evoked Intrinsic Imaging Signals in the Olfactory Bulb Are Independent of Neurovascular Coupling. Cell Rep 2015; 12:313-25. [PMID: 26146075 PMCID: PMC5066842 DOI: 10.1016/j.celrep.2015.06.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 05/12/2015] [Accepted: 06/03/2015] [Indexed: 11/19/2022] Open
Abstract
Functional brain-imaging techniques used in humans and animals, such as functional MRI and intrinsic optical signal (IOS) imaging, are thought to largely rely on neurovascular coupling and hemodynamic responses. Here, taking advantage of the well-described micro-architecture of the mouse olfactory bulb, we dissected the nature of odor-evoked IOSs. Using in vivo pharmacology in transgenic mouse lines reporting activity in different cell types, we show that parenchymal IOSs are largely independent of neurotransmitter release and neurovascular coupling. Furthermore, our results suggest that odor-evoked parenchymal IOSs originate from changes in light scattering of olfactory sensory neuron axons, mostly due to water movement following action potential propagation. Our study sheds light on a direct correlate of neuronal activity, which may be used for large-scale functional brain imaging.
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Affiliation(s)
- Roberto Vincis
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1211 Geneva, Switzerland; Geneva Neuroscience Center, University of Geneva, 1211 Geneva, Switzerland
| | - Samuel Lagier
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1211 Geneva, Switzerland; Geneva Neuroscience Center, University of Geneva, 1211 Geneva, Switzerland
| | - Dimitri Van De Ville
- Geneva Neuroscience Center, University of Geneva, 1211 Geneva, Switzerland; Department of Radiology and Medical Informatics, University of Geneva, 1211 Geneva, Switzerland; Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Ivan Rodriguez
- Geneva Neuroscience Center, University of Geneva, 1211 Geneva, Switzerland; Department of Genetics and Evolution, University of Geneva, 1211 Geneva, Switzerland.
| | - Alan Carleton
- Department of Basic Neurosciences, School of Medicine, University of Geneva, 1211 Geneva, Switzerland; Geneva Neuroscience Center, University of Geneva, 1211 Geneva, Switzerland.
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36
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Hamel EJO, Grewe BF, Parker JG, Schnitzer MJ. Cellular level brain imaging in behaving mammals: an engineering approach. Neuron 2015; 86:140-59. [PMID: 25856491 PMCID: PMC5758309 DOI: 10.1016/j.neuron.2015.03.055] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Fluorescence imaging offers expanding capabilities for recording neural dynamics in behaving mammals, including the means to monitor hundreds of cells targeted by genetic type or connectivity, track cells over weeks, densely sample neurons within local microcircuits, study cells too inactive to isolate in extracellular electrical recordings, and visualize activity in dendrites, axons, or dendritic spines. We discuss recent progress and future directions for imaging in behaving mammals from a systems engineering perspective, which seeks holistic consideration of fluorescent indicators, optical instrumentation, and computational analyses. Today, genetically encoded indicators of neural Ca(2+) dynamics are widely used, and those of trans-membrane voltage are rapidly improving. Two complementary imaging paradigms involve conventional microscopes for studying head-restrained animals and head-mounted miniature microscopes for imaging in freely behaving animals. Overall, the field has attained sufficient sophistication that increased cooperation between those designing new indicators, light sources, microscopes, and computational analyses would greatly benefit future progress.
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Affiliation(s)
| | | | - Jones G Parker
- CNC Program, Stanford University, Stanford, CA 94305, USA; Pfizer Neuroscience Research Unit, Cambridge, MA 02139, USA
| | - Mark J Schnitzer
- CNC Program, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA.
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37
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Nunez-Parra A, Li A, Restrepo D. Coding odor identity and odor value in awake rodents. PROGRESS IN BRAIN RESEARCH 2015; 208:205-22. [PMID: 24767484 DOI: 10.1016/b978-0-444-63350-7.00008-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
In the last decade, drastic changes in the understanding of the role of the olfactory bulb and piriform cortex in odor detection have taken place through awake behaving recording in rodents. It is clear that odor responses in mitral and granule cells are strikingly different in the olfactory bulb of anesthetized versus awake animals. In addition, sniff recording has evidenced that mitral cell responses to odors during the sniff can convey information on the odor identity and sniff phase. Moreover, we review studies that show that the mitral cell conveys information on not only odor identity but also whether the odor is rewarded or not (odor value). Finally, we discuss how the substantial increase in awake behaving recording raises questions for future studies.
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Affiliation(s)
- Alexia Nunez-Parra
- Department of Cell and Developmental Biology, Rocky Mountain Taste and Smell Center and Neuroscience Program, University of Colorado Medical School, Aurora, CO, USA
| | - Anan Li
- Department of Cell and Developmental Biology, Rocky Mountain Taste and Smell Center and Neuroscience Program, University of Colorado Medical School, Aurora, CO, USA; State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, The Chinese Academy of Sciences, Wuhan, China
| | - Diego Restrepo
- Department of Cell and Developmental Biology, Rocky Mountain Taste and Smell Center and Neuroscience Program, University of Colorado Medical School, Aurora, CO, USA.
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38
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Yuan Q, Harley CW. Learning modulation of odor representations: new findings from Arc-indexed networks. Front Cell Neurosci 2015; 8:423. [PMID: 25565958 PMCID: PMC4271698 DOI: 10.3389/fncel.2014.00423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Accepted: 11/23/2014] [Indexed: 11/13/2022] Open
Abstract
We first review our understanding of odor representations in rodent olfactory bulb (OB) and anterior piriform cortex (APC). We then consider learning-induced representation changes. Finally we describe the perspective on network representations gained from examining Arc-indexed odor networks of awake rats. Arc-indexed networks are sparse and distributed, consistent with current views. However Arc provides representations of repeated odors. Arc-indexed repeated odor representations are quite variable. Sparse representations are assumed to be compact and reliable memory codes. Arc suggests this is not necessarily the case. The variability seen is consistent with electrophysiology in awake animals and may reflect top-down cortical modulation of context. Arc-indexing shows that distinct odors share larger than predicted neuron pools. These may be low-threshold neuronal subsets. Learning’s effect on Arc-indexed representations is to increase the stable or overlapping component of rewarded odor representations. This component can decrease for similar odors when their discrimination is rewarded. The learning effects seen are supported by electrophysiology, but mechanisms remain to be elucidated.
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Affiliation(s)
- Qi Yuan
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland St. John's, NL, Canada
| | - Carolyn W Harley
- Department of Psychology, Faculty of Science, Memorial University of Newfoundland St. John's, NL, Canada
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39
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Leng G, Hashimoto H, Tsuji C, Sabatier N, Ludwig M. Discharge patterning in rat olfactory bulb mitral cells in vivo. Physiol Rep 2014; 2:e12021. [PMID: 25281614 PMCID: PMC4254087 DOI: 10.14814/phy2.12021] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Revised: 04/18/2014] [Accepted: 04/18/2014] [Indexed: 11/24/2022] Open
Abstract
Here we present a detailed statistical analysis of the discharge characteristics of mitral cells of the main olfactory bulb of urethane-anesthetized rats. Neurons were recorded from the mitral cell layer, and antidromically identified by stimuli applied to the lateral olfactory tract. All mitral cells displayed repeated, prolonged bursts of action potentials typically lasting >100 sec and separated by similarly long intervals; about half were completely silent between bursts. No such bursting was observed in nonmitral cells recorded in close proximity to mitral cells. Bursts were asynchronous among even adjacent mitral cells. The intraburst activity of most mitral cells showed strong entrainment to the spontaneous respiratory rhythm; similar entrainment was seen in some, but not all nonmitral cells. All mitral cells displayed a peak of excitability at ~25 msec after spikes, as reflected by a peak in the interspike interval distribution and in the corresponding hazard function. About half also showed a peak at about 6 msec, reflecting the common occurrence of doublet spikes. Nonmitral cells showed no such doublet spikes. Bursts typically increased in intensity over the first 20-30 sec of a burst, during which time doublets were rare or absent. After 20-30 sec (in cells that exhibited doublets), doublets occurred frequently for as long as the burst persisted, in trains of up to 10 doublets. The last doublet was followed by an extended relative refractory period the duration of which was independent of train length. In cells that were excited by application of a particular odor, responsiveness was apparently greater during silent periods between bursts than during bursts. Conversely in cells that were inhibited by a particular odor, responsiveness was only apparent when cells were active. Extensive raw (event timing) data from the cells, together with details of those analyses, are provided as supplementary material, freely available for secondary use by others.
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Affiliation(s)
- Gareth Leng
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK
| | - Hirofumi Hashimoto
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK
| | - Chiharu Tsuji
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK
| | - Nancy Sabatier
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK
| | - Mike Ludwig
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK
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40
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Sheridan DC, Hughes AR, Erdélyi F, Szabó G, Hentges ST, Schoppa NE. Matching of feedback inhibition with excitation ensures fidelity of information flow in the anterior piriform cortex. Neuroscience 2014; 275:519-30. [PMID: 24969131 DOI: 10.1016/j.neuroscience.2014.06.033] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 05/24/2014] [Accepted: 06/12/2014] [Indexed: 11/18/2022]
Abstract
Odor-evoked responses in mitral cells of the olfactory bulb are characterized by prolonged patterns of action potential (spike) activity. If downstream neurons are to respond to each spike in these patterns, the duration of the excitatory response to one spike should be limited, enabling cells to respond to subsequent spikes. To test for such mechanisms, we performed patch-clamp recordings in slices of the mouse anterior piriform cortex. Mitral cell axons in the lateral olfactory tract (LOT) were stimulated electrically at different intensities and with various frequency patterns to mimic changing input conditions that the piriform cortex likely encounters in vivo. We found with cell-attached measurements that superficial pyramidal (SP) cells in layer 2 consistently responded to LOT stimulation across conditions with a limited number (1-2) of spikes per stimulus pulse. The key synaptic feature accounting for the limited spike number appeared to be somatic inhibition derived from layer 3 fast-spiking cells. This inhibition tracked the timing of the first spike in SP cells across conditions, which naturally limited the spike number to 1-2. These response features to LOT stimulation were, moreover, not unique to SP cells, also occurring in a population of fluorescently labeled interneurons in glutamic acid decarboxylase 65-eGFP mice. That these different cortical cells respond to incoming inputs with 1-2 spikes per stimulus may be especially critical for relaying bulbar information contained in synchronized oscillations at beta (15-30Hz) or gamma (30-80Hz) frequencies.
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Affiliation(s)
- D C Sheridan
- University of Colorado Anschutz Medical Campus, Department of Physiology & Biophysics, 12800 East 19th Avenue, Aurora, CO 80045, United States.
| | - A R Hughes
- Department of Biomedical Sciences, Colorado State University, 1680 Campus Delivery, Fort Collins, CO 80523, United States
| | - F Erdélyi
- Institute of Experimental Medicine, Division of Medical Gene Technology, Budapest, Hungary
| | - G Szabó
- Institute of Experimental Medicine, Division of Medical Gene Technology, Budapest, Hungary.
| | - S T Hentges
- Department of Biomedical Sciences, Colorado State University, 1680 Campus Delivery, Fort Collins, CO 80523, United States.
| | - N E Schoppa
- University of Colorado Anschutz Medical Campus, Department of Physiology & Biophysics, 12800 East 19th Avenue, Aurora, CO 80045, United States.
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41
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A population of glomerular glutamatergic neurons controls sensory information transfer in the mouse olfactory bulb. Nat Commun 2014; 5:3791. [PMID: 24804702 PMCID: PMC4028618 DOI: 10.1038/ncomms4791] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 04/02/2014] [Indexed: 12/29/2022] Open
Abstract
In sensory systems, peripheral organs convey sensory inputs to relay networks where information is shaped by local microcircuits before being transmitted to cortical areas. In the olfactory system, odorants evoke specific patterns of sensory neuron activity which are transmitted to output neurons in olfactory bulb glomeruli. How sensory information is transferred and shaped at this level remains still unclear. Here we employ mouse genetics, 2-photon microscopy, electrophysiology and optogenetics, to identify a novel population of glutamatergic neurons (VGLUT3+) in the glomerular layer of the adult mouse olfactory bulb as well as several of their synaptic targets. Both peripheral and serotoninergic inputs control VGLUT3+ neurons firing. Furthermore, we show that VGLUT3+ neurons photostimulation in vivo strongly suppresses both spontaneous and odor-evoked firing of bulbar output neurons. In conclusion, we identify and characterize here a microcircuit controlling the transfer of sensory information at an early stage of the olfactory pathway.
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42
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Abraham NM, Vincis R, Lagier S, Rodriguez I, Carleton A. Long term functional plasticity of sensory inputs mediated by olfactory learning. eLife 2014; 3:e02109. [PMID: 24642413 PMCID: PMC3953949 DOI: 10.7554/elife.02109] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Sensory inputs are remarkably organized along all sensory pathways. While sensory representations are known to undergo plasticity at the higher levels of sensory pathways following peripheral lesions or sensory experience, less is known about the functional plasticity of peripheral inputs induced by learning. We addressed this question in the adult mouse olfactory system by combining odor discrimination studies with functional imaging of sensory input activity in awake mice. Here we show that associative learning, but not passive odor exposure, potentiates the strength of sensory inputs up to several weeks after the end of training. We conclude that experience-dependent plasticity can occur in the periphery of adult mouse olfactory system, which should improve odor detection and contribute towards accurate and fast odor discriminations. DOI:http://dx.doi.org/10.7554/eLife.02109.001 The mammalian brain is not static, but instead retains a significant degree of plasticity throughout an animal’s life. It is this plasticity that enables adults to learn new things, adjust to new environments and, to some degree, regain functions they have lost as a result of brain damage. However, information about the environment must first be detected and encoded by the senses. Odors, for example, activate specific receptors in the nose, and these in turn project to structures called glomeruli in a region of the brain known as the olfactory bulb. Each odor activates a unique combination of glomeruli, and the information contained within this ‘odor fingerprint’ is relayed via olfactory bulb neurons to the olfactory cortex. Now, Abraham et al. have revealed that the earliest stages of odor processing also show plasticity in adult animals. Two groups of mice were exposed to the same two odors: however, the first group was trained to discriminate between the odors to obtain a reward, whereas the second group was passively exposed to them. When both groups of mice were subsequently re-exposed to the odors, the trained group activated more glomeruli, more strongly, than a control group that had never encountered the odors before. By contrast, the responses of mice in the passively exposed group did not differ from those of a control group. Given that the response of glomeruli correlates with the ability of mice to discriminate between odors, these results suggest that trained animals would now be able to discriminate between the odors more easily than other mice. In other words, sensory plasticity ensures that stimuli that have been associatively learned with or without reward will be easier to detect should they be encountered again in the future. DOI:http://dx.doi.org/10.7554/eLife.02109.002
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Affiliation(s)
- Nixon M Abraham
- Department of Basic Neurosciences, School of Medicine, University of Geneva, Geneva, Switzerland
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Burton SD, Urban NN. Greater excitability and firing irregularity of tufted cells underlies distinct afferent-evoked activity of olfactory bulb mitral and tufted cells. J Physiol 2014; 592:2097-118. [PMID: 24614745 DOI: 10.1113/jphysiol.2013.269886] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Mitral and tufted cells, the two classes of principal neurons in the mammalian main olfactory bulb, exhibit morphological differences but remain widely viewed as functionally equivalent. Results from several recent studies, however, suggest that these two cell classes may encode complementary olfactory information in their distinct patterns of afferent-evoked activity. To understand how these differences in activity arise, we have performed the first systematic comparison of synaptic and intrinsic properties between mitral and tufted cells. Consistent with previous studies, we found that tufted cells fire with higher probability and rates and shorter latencies than mitral cells in response to physiological afferent stimulation. This stronger response of tufted cells could be partially attributed to synaptic differences, as tufted cells received stronger afferent-evoked excitation than mitral cells. However, differences in intrinsic excitability also contributed to the differences between mitral and tufted cell activity. Compared to mitral cells, tufted cells exhibited twofold greater excitability and peak instantaneous firing rates. These differences in excitability probably arise from differential expression of voltage-gated potassium currents, as tufted cells exhibited faster action potential repolarization and afterhyperpolarizations than mitral cells. Surprisingly, mitral and tufted cells also showed firing mode differences. While both cell classes exhibited regular firing and irregular stuttering of action potential clusters, tufted cells demonstrated a greater propensity to stutter than mitral cells. Collectively, stronger afferent-evoked excitation, greater intrinsic excitability and more irregular firing in tufted cells can combine to drive distinct responses of mitral and tufted cells to afferent-evoked input.
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Affiliation(s)
- Shawn D Burton
- Department of Biological Sciences, Center for the Neural Basis of Cognition, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Nathaniel N Urban
- Department of Biological Sciences, Center for the Neural Basis of Cognition, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
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Kaplan BA, Lansner A. A spiking neural network model of self-organized pattern recognition in the early mammalian olfactory system. Front Neural Circuits 2014; 8:5. [PMID: 24570657 PMCID: PMC3916767 DOI: 10.3389/fncir.2014.00005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Accepted: 01/09/2014] [Indexed: 01/01/2023] Open
Abstract
Olfactory sensory information passes through several processing stages before an odor percept emerges. The question how the olfactory system learns to create odor representations linking those different levels and how it learns to connect and discriminate between them is largely unresolved. We present a large-scale network model with single and multi-compartmental Hodgkin-Huxley type model neurons representing olfactory receptor neurons (ORNs) in the epithelium, periglomerular cells, mitral/tufted cells and granule cells in the olfactory bulb (OB), and three types of cortical cells in the piriform cortex (PC). Odor patterns are calculated based on affinities between ORNs and odor stimuli derived from physico-chemical descriptors of behaviorally relevant real-world odorants. The properties of ORNs were tuned to show saturated response curves with increasing concentration as seen in experiments. On the level of the OB we explored the possibility of using a fuzzy concentration interval code, which was implemented through dendro-dendritic inhibition leading to winner-take-all like dynamics between mitral/tufted cells belonging to the same glomerulus. The connectivity from mitral/tufted cells to PC neurons was self-organized from a mutual information measure and by using a competitive Hebbian-Bayesian learning algorithm based on the response patterns of mitral/tufted cells to different odors yielding a distributed feed-forward projection to the PC. The PC was implemented as a modular attractor network with a recurrent connectivity that was likewise organized through Hebbian-Bayesian learning. We demonstrate the functionality of the model in a one-sniff-learning and recognition task on a set of 50 odorants. Furthermore, we study its robustness against noise on the receptor level and its ability to perform concentration invariant odor recognition. Moreover, we investigate the pattern completion capabilities of the system and rivalry dynamics for odor mixtures.
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Affiliation(s)
- Bernhard A Kaplan
- Department of Computational Biology, School of Computer Science and Communication, Royal Institute of Technology Stockholm, Sweden ; Stockholm Brain Institute, Karolinska Institute Stockholm, Sweden
| | - Anders Lansner
- Department of Computational Biology, School of Computer Science and Communication, Royal Institute of Technology Stockholm, Sweden ; Stockholm Brain Institute, Karolinska Institute Stockholm, Sweden ; Department of Numerical Analysis and Computer Science, Stockholm University Stockholm, Sweden
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Doll CA, Broadie K. Impaired activity-dependent neural circuit assembly and refinement in autism spectrum disorder genetic models. Front Cell Neurosci 2014; 8:30. [PMID: 24570656 PMCID: PMC3916725 DOI: 10.3389/fncel.2014.00030] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 01/21/2014] [Indexed: 01/23/2023] Open
Abstract
Early-use activity during circuit-specific critical periods refines brain circuitry by the coupled processes of eliminating inappropriate synapses and strengthening maintained synapses. We theorize these activity-dependent (A-D) developmental processes are specifically impaired in autism spectrum disorders (ASDs). ASD genetic models in both mouse and Drosophila have pioneered our insights into normal A-D neural circuit assembly and consolidation, and how these developmental mechanisms go awry in specific genetic conditions. The monogenic fragile X syndrome (FXS), a common cause of heritable ASD and intellectual disability, has been particularly well linked to defects in A-D critical period processes. The fragile X mental retardation protein (FMRP) is positively activity-regulated in expression and function, in turn regulates excitability and activity in a negative feedback loop, and appears to be required for the A-D remodeling of synaptic connectivity during early-use critical periods. The Drosophila FXS model has been shown to functionally conserve the roles of human FMRP in synaptogenesis, and has been centrally important in generating our current mechanistic understanding of the FXS disease state. Recent advances in Drosophila optogenetics, transgenic calcium reporters, highly-targeted transgenic drivers for individually-identified neurons, and a vastly improved connectome of the brain are now being combined to provide unparalleled opportunities to both manipulate and monitor A-D processes during critical period brain development in defined neural circuits. The field is now poised to exploit this new Drosophila transgenic toolbox for the systematic dissection of A-D mechanisms in normal versus ASD brain development, particularly utilizing the well-established Drosophila FXS disease model.
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Affiliation(s)
- Caleb A Doll
- Department of Biological Sciences, Vanderbilt University Nashville, TN, USA
| | - Kendal Broadie
- Department of Biological Sciences, Vanderbilt University Nashville, TN, USA ; Kennedy Center for Research on Human Development, Vanderbilt University Nashville, TN, USA
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