51
|
Dvořáček J, Bednářová A, Krishnan N, Kodrík D. Dopaminergic muhsroom body neurons in Drosophila: flexibility of neuron identity in a model organism? Neurosci Biobehav Rev 2022; 135:104570. [DOI: 10.1016/j.neubiorev.2022.104570] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 02/03/2022] [Accepted: 02/03/2022] [Indexed: 11/28/2022]
|
52
|
Weiss JT, Donlea JM. Roles for Sleep in Neural and Behavioral Plasticity: Reviewing Variation in the Consequences of Sleep Loss. Front Behav Neurosci 2022; 15:777799. [PMID: 35126067 PMCID: PMC8810646 DOI: 10.3389/fnbeh.2021.777799] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 12/16/2021] [Indexed: 12/13/2022] Open
Abstract
Sleep is a vital physiological state that has been broadly conserved across the evolution of animal species. While the precise functions of sleep remain poorly understood, a large body of research has examined the negative consequences of sleep loss on neural and behavioral plasticity. While sleep disruption generally results in degraded neural plasticity and cognitive function, the impact of sleep loss can vary widely with age, between individuals, and across physiological contexts. Additionally, several recent studies indicate that sleep loss differentially impacts distinct neuronal populations within memory-encoding circuitry. These findings indicate that the negative consequences of sleep loss are not universally shared, and that identifying conditions that influence the resilience of an organism (or neuron type) to sleep loss might open future opportunities to examine sleep's core functions in the brain. Here, we discuss the functional roles for sleep in adaptive plasticity and review factors that can contribute to individual variations in sleep behavior and responses to sleep loss.
Collapse
Affiliation(s)
- Jacqueline T. Weiss
- Department of Neurobiology, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA, United States
- Neuroscience Interdepartmental Program, University of California, Los Angeles, Los Angeles, CA, United States
| | - Jeffrey M. Donlea
- Department of Neurobiology, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA, United States
- *Correspondence: Jeffrey M. Donlea
| |
Collapse
|
53
|
Pribbenow C, Chen YC, Heim MM, Laber D, Reubold S, Reynolds E, Balles I, Fernández-d V Alquicira T, Suárez-Grimalt R, Scheunemann L, Rauch C, Matkovic T, Rösner J, Lichtner G, Jagannathan SR, Owald D. Postsynaptic plasticity of cholinergic synapses underlies the induction and expression of appetitive and familiarity memories in Drosophila. eLife 2022; 11:80445. [PMID: 36250621 PMCID: PMC9733945 DOI: 10.7554/elife.80445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 10/17/2022] [Indexed: 12/14/2022] Open
Abstract
In vertebrates, several forms of memory-relevant synaptic plasticity involve postsynaptic rearrangements of glutamate receptors. In contrast, previous work indicates that Drosophila and other invertebrates store memories using presynaptic plasticity of cholinergic synapses. Here, we provide evidence for postsynaptic plasticity at cholinergic output synapses from the Drosophila mushroom bodies (MBs). We find that the nicotinic acetylcholine receptor (nAChR) subunit α5 is required within specific MB output neurons for appetitive memory induction but is dispensable for aversive memories. In addition, nAChR α2 subunits mediate memory expression and likely function downstream of α5 and the postsynaptic scaffold protein discs large (Dlg). We show that postsynaptic plasticity traces can be induced independently of the presynapse, and that in vivo dynamics of α2 nAChR subunits are changed both in the context of associative and non-associative (familiarity) memory formation, underlying different plasticity rules. Therefore, regardless of neurotransmitter identity, key principles of postsynaptic plasticity support memory storage across phyla.
Collapse
Affiliation(s)
- Carlotta Pribbenow
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Yi-chun Chen
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - M-Marcel Heim
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Desiree Laber
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Silas Reubold
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Eric Reynolds
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Isabella Balles
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Tania Fernández-d V Alquicira
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Raquel Suárez-Grimalt
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany,Einstein Center for Neurosciences BerlinBerlinGermany
| | - Lisa Scheunemann
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany,NeuroCure, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany,Institut für Biologie, Freie Universität BerlinBerlinGermany
| | - Carolin Rauch
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Tanja Matkovic
- Institut für Biologie, Freie Universität BerlinBerlinGermany
| | - Jörg Rösner
- NWFZ, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthGreifswaldGermany
| | - Gregor Lichtner
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany,Universitätsmedizin Greifswald, Department of Anesthesia, Critical Care, Emergency and Pain MedicineGreifswaldGermany
| | - Sridhar R Jagannathan
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - David Owald
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany,Einstein Center for Neurosciences BerlinBerlinGermany,NeuroCure, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| |
Collapse
|
54
|
Prisco L, Deimel SH, Yeliseyeva H, Fiala A, Tavosanis G. The anterior paired lateral neuron normalizes odour-evoked activity in the Drosophila mushroom body calyx. eLife 2021; 10:e74172. [PMID: 34964714 PMCID: PMC8741211 DOI: 10.7554/elife.74172] [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: 09/23/2021] [Accepted: 12/28/2021] [Indexed: 11/25/2022] Open
Abstract
To identify and memorize discrete but similar environmental inputs, the brain needs to distinguish between subtle differences of activity patterns in defined neuronal populations. The Kenyon cells (KCs) of the Drosophila adult mushroom body (MB) respond sparsely to complex olfactory input, a property that is thought to support stimuli discrimination in the MB. To understand how this property emerges, we investigated the role of the inhibitory anterior paired lateral (APL) neuron in the input circuit of the MB, the calyx. Within the calyx, presynaptic boutons of projection neurons (PNs) form large synaptic microglomeruli (MGs) with dendrites of postsynaptic KCs. Combining electron microscopy (EM) data analysis and in vivo calcium imaging, we show that APL, via inhibitory and reciprocal synapses targeting both PN boutons and KC dendrites, normalizes odour-evoked representations in MGs of the calyx. APL response scales with the PN input strength and is regionalized around PN input distribution. Our data indicate that the formation of a sparse code by the KCs requires APL-driven normalization of their MG postsynaptic responses. This work provides experimental insights on how inhibition shapes sensory information representation in a higher brain centre, thereby supporting stimuli discrimination and allowing for efficient associative memory formation.
Collapse
Affiliation(s)
- Luigi Prisco
- Dynamics of neuronal circuits, German Center for Neurodegenerative Diseases (DZNE)BonnGermany
| | | | - Hanna Yeliseyeva
- Dynamics of neuronal circuits, German Center for Neurodegenerative Diseases (DZNE)BonnGermany
| | - André Fiala
- Department of Molecular Neurobiology of Behavior, University of GöttingenGöttingenGermany
| | - Gaia Tavosanis
- Dynamics of neuronal circuits, German Center for Neurodegenerative Diseases (DZNE)BonnGermany
- LIMES, Rheinische Friedrich Wilhelms Universität BonnBonnGermany
| |
Collapse
|
55
|
Abdelrahman NY, Vasilaki E, Lin AC. Compensatory variability in network parameters enhances memory performance in the Drosophila mushroom body. Proc Natl Acad Sci U S A 2021; 118:e2102158118. [PMID: 34845010 PMCID: PMC8670477 DOI: 10.1073/pnas.2102158118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/06/2021] [Indexed: 11/18/2022] Open
Abstract
Neural circuits use homeostatic compensation to achieve consistent behavior despite variability in underlying intrinsic and network parameters. However, it remains unclear how compensation regulates variability across a population of the same type of neurons within an individual and what computational benefits might result from such compensation. We address these questions in the Drosophila mushroom body, the fly's olfactory memory center. In a computational model, we show that under sparse coding conditions, memory performance is degraded when the mushroom body's principal neurons, Kenyon cells (KCs), vary realistically in key parameters governing their excitability. However, memory performance is rescued while maintaining realistic variability if parameters compensate for each other to equalize KC average activity. Such compensation can be achieved through both activity-dependent and activity-independent mechanisms. Finally, we show that correlations predicted by our model's compensatory mechanisms appear in the Drosophila hemibrain connectome. These findings reveal compensatory variability in the mushroom body and describe its computational benefits for associative memory.
Collapse
Affiliation(s)
- Nada Y Abdelrahman
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, United Kingdom
- Department of Computer Science, University of Sheffield, Sheffield S1 4DP, United Kingdom
- Neuroscience Institute, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Eleni Vasilaki
- Department of Computer Science, University of Sheffield, Sheffield S1 4DP, United Kingdom
- Neuroscience Institute, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Andrew C Lin
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, United Kingdom;
- Neuroscience Institute, University of Sheffield, Sheffield S10 2TN, United Kingdom
| |
Collapse
|
56
|
Pannunzi M, Nowotny T. Non-synaptic interactions between olfactory receptor neurons, a possible key feature of odor processing in flies. PLoS Comput Biol 2021; 17:e1009583. [PMID: 34898600 PMCID: PMC8668107 DOI: 10.1371/journal.pcbi.1009583] [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: 07/05/2021] [Accepted: 10/22/2021] [Indexed: 11/28/2022] Open
Abstract
When flies explore their environment, they encounter odors in complex, highly intermittent plumes. To navigate a plume and, for example, find food, they must solve several challenges, including reliably identifying mixtures of odorants and their intensities, and discriminating odorant mixtures emanating from a single source from odorants emitted from separate sources and just mixing in the air. Lateral inhibition in the antennal lobe is commonly understood to help solving these challenges. With a computational model of the Drosophila olfactory system, we analyze the utility of an alternative mechanism for solving them: Non-synaptic ("ephaptic") interactions (NSIs) between olfactory receptor neurons that are stereotypically co-housed in the same sensilla. We find that NSIs improve mixture ratio detection and plume structure sensing and do so more efficiently than the traditionally considered mechanism of lateral inhibition in the antennal lobe. The best performance is achieved when both mechanisms work in synergy. However, we also found that NSIs decrease the dynamic range of co-housed ORNs, especially when they have similar sensitivity to an odorant. These results shed light, from a functional perspective, on the role of NSIs, which are normally avoided between neurons, for instance by myelination.
Collapse
Affiliation(s)
- Mario Pannunzi
- School of Engineering and Informatics, University of Sussex, Brighton, United Kingdom
| | - Thomas Nowotny
- School of Engineering and Informatics, University of Sussex, Brighton, United Kingdom
| |
Collapse
|
57
|
Guzman SJ, Schlögl A, Espinoza C, Zhang X, Suter BA, Jonas P. How connectivity rules and synaptic properties shape the efficacy of pattern separation in the entorhinal cortex-dentate gyrus-CA3 network. NATURE COMPUTATIONAL SCIENCE 2021; 1:830-842. [PMID: 38217181 DOI: 10.1038/s43588-021-00157-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Accepted: 10/12/2021] [Indexed: 01/15/2024]
Abstract
Pattern separation is a fundamental brain computation that converts small differences in input patterns into large differences in output patterns. Several synaptic mechanisms of pattern separation have been proposed, including code expansion, inhibition and plasticity; however, which of these mechanisms play a role in the entorhinal cortex (EC)-dentate gyrus (DG)-CA3 circuit, a classical pattern separation circuit, remains unclear. Here we show that a biologically realistic, full-scale EC-DG-CA3 circuit model, including granule cells (GCs) and parvalbumin-positive inhibitory interneurons (PV+-INs) in the DG, is an efficient pattern separator. Both external gamma-modulated inhibition and internal lateral inhibition mediated by PV+-INs substantially contributed to pattern separation. Both local connectivity and fast signaling at GC-PV+-IN synapses were important for maximum effectiveness. Similarly, mossy fiber synapses with conditional detonator properties contributed to pattern separation. By contrast, perforant path synapses with Hebbian synaptic plasticity and direct EC-CA3 connection shifted the network towards pattern completion. Our results demonstrate that the specific properties of cells and synapses optimize higher-order computations in biological networks and might be useful to improve the deep learning capabilities of technical networks.
Collapse
Affiliation(s)
- S Jose Guzman
- IST Austria, Klosterneuburg, Austria
- Institute of Molecular Biotechnology, Vienna, Austria
| | | | - Claudia Espinoza
- IST Austria, Klosterneuburg, Austria
- Medical University of Austria, Division of Cognitive Neurobiology, Vienna, Austria
| | - Xiaomin Zhang
- IST Austria, Klosterneuburg, Austria
- Brain Research Institute, University of Zürich, Zurich, Switzerland
| | | | | |
Collapse
|
58
|
Wang PY, Sun Y, Axel R, Abbott LF, Yang GR. Evolving the olfactory system with machine learning. Neuron 2021; 109:3879-3892.e5. [PMID: 34619093 DOI: 10.1016/j.neuron.2021.09.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 08/09/2021] [Accepted: 09/08/2021] [Indexed: 11/27/2022]
Abstract
The convergent evolution of the fly and mouse olfactory system led us to ask whether the anatomic connectivity and functional logic of olfactory circuits would evolve in artificial neural networks trained to perform olfactory tasks. Artificial networks trained to classify odor identity recapitulate the connectivity inherent in the olfactory system. Input units are driven by a single receptor type, and units driven by the same receptor converge to form a glomerulus. Glomeruli exhibit sparse, unstructured connectivity onto a larger expansion layer of Kenyon cells. When trained to both classify odor identity and to impart innate valence onto odors, the network develops independent pathways for identity and valence classification. Thus, the defining features of fly and mouse olfactory systems also evolved in artificial neural networks trained to perform olfactory tasks. This implies that convergent evolution reflects an underlying logic rather than shared developmental principles.
Collapse
Affiliation(s)
- Peter Y Wang
- The Mortimer B. Zuckerman Mind Brain Behavior Institute, Department of Neuroscience, Columbia University, New York, NY 10027, USA
| | - Yi Sun
- Department of Mathematics, Columbia University, New York, NY 10027, USA
| | - Richard Axel
- The Mortimer B. Zuckerman Mind Brain Behavior Institute, Department of Neuroscience, Columbia University, New York, NY 10027, USA; Howard Hughes Medical Institute, Columbia University, New York, NY 10027, USA
| | - L F Abbott
- The Mortimer B. Zuckerman Mind Brain Behavior Institute, Department of Neuroscience, Columbia University, New York, NY 10027, USA
| | - Guangyu Robert Yang
- The Mortimer B. Zuckerman Mind Brain Behavior Institute, Department of Neuroscience, Columbia University, New York, NY 10027, USA.
| |
Collapse
|
59
|
Vrontou E, Groschner LN, Szydlowski S, Brain R, Krebbers A, Miesenböck G. Response competition between neurons and antineurons in the mushroom body. Curr Biol 2021; 31:4911-4922.e4. [PMID: 34610272 PMCID: PMC8612741 DOI: 10.1016/j.cub.2021.09.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 08/03/2021] [Accepted: 09/03/2021] [Indexed: 11/04/2022]
Abstract
The mushroom bodies of Drosophila contain circuitry compatible with race models of perceptual choice. When flies discriminate odor intensity differences, opponent pools of αβ core Kenyon cells (on and off αβc KCs) accumulate evidence for increases or decreases in odor concentration. These sensory neurons and “antineurons” connect to a layer of mushroom body output neurons (MBONs) which bias behavioral intent in opposite ways. All-to-all connectivity between the competing integrators and their MBON partners allows for correct and erroneous decisions; dopaminergic reinforcement sets choice probabilities via reciprocal changes to the efficacies of on and off KC synapses; and pooled inhibition between αβc KCs can establish equivalence with the drift-diffusion formalism known to describe behavioral performance. The response competition network gives tangible form to many features envisioned in theoretical models of mammalian decision making, but it differs from these models in one respect: the principal variables—the fill levels of the integrators and the strength of inhibition between them—are represented by graded potentials rather than spikes. In pursuit of similar computational goals, a small brain may thus prioritize the large information capacity of analog signals over the robustness and temporal processing span of pulsatile codes. Mushroom body output neurons respond with excitation to odor on- and offset On and off responses reflect the convergence of oppositely tuned Kenyon cells (KCs) Opponent KCs compete by eliciting inhibitory feedback from a common interneuron pool KCs and interneurons communicate through graded potentials rather than spikes
Collapse
Affiliation(s)
- Eleftheria Vrontou
- Centre for Neural Circuits and Behaviour, University of Oxford, Tinsley Building, Mansfield Road, Oxford OX1 3SR, UK
| | - Lukas N Groschner
- Centre for Neural Circuits and Behaviour, University of Oxford, Tinsley Building, Mansfield Road, Oxford OX1 3SR, UK
| | - Susanne Szydlowski
- Centre for Neural Circuits and Behaviour, University of Oxford, Tinsley Building, Mansfield Road, Oxford OX1 3SR, UK
| | - Ruth Brain
- Centre for Neural Circuits and Behaviour, University of Oxford, Tinsley Building, Mansfield Road, Oxford OX1 3SR, UK
| | - Alina Krebbers
- Centre for Neural Circuits and Behaviour, University of Oxford, Tinsley Building, Mansfield Road, Oxford OX1 3SR, UK
| | - Gero Miesenböck
- Centre for Neural Circuits and Behaviour, University of Oxford, Tinsley Building, Mansfield Road, Oxford OX1 3SR, UK.
| |
Collapse
|
60
|
Noyes NC, Phan A, Davis RL. Memory suppressor genes: Modulating acquisition, consolidation, and forgetting. Neuron 2021; 109:3211-3227. [PMID: 34450024 PMCID: PMC8542634 DOI: 10.1016/j.neuron.2021.08.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 07/15/2021] [Accepted: 07/30/2021] [Indexed: 02/06/2023]
Abstract
The brain has a remarkable but underappreciated capacity to limit memory formation and expression. The term "memory suppressor gene" was coined in 1998 as an attempt to explain emerging reports that some genes appeared to limit memory. At that time, only a handful of memory suppressor genes were known, and they were understood to work by limiting cAMP-dependent consolidation. In the intervening decades, almost 100 memory suppressor genes with diverse functions have been discovered that affect not only consolidation but also acquisition and forgetting. Here we highlight the surprising extent to which biological limits are placed on memory formation through reviewing the literature on memory suppressor genes. In this review, we present memory suppressors within the framework of their actions on different memory operations: acquisition, consolidation, and forgetting. This is followed by a discussion of the reasons why there may be a biological need to limit memory formation.
Collapse
Affiliation(s)
- Nathaniel C Noyes
- Department of Neuroscience, Scripps Research Institute Florida, Jupiter, FL 33458, USA
| | - Anna Phan
- Department of Biological Sciences, University of Alberta, 11355 Saskatchewan Drive, Edmonton, AB T6G 2E9, Canada
| | - Ronald L Davis
- Department of Neuroscience, Scripps Research Institute Florida, Jupiter, FL 33458, USA.
| |
Collapse
|
61
|
Glas A, Hübener M, Bonhoeffer T, Goltstein PM. Spaced training enhances memory and prefrontal ensemble stability in mice. Curr Biol 2021; 31:4052-4061.e6. [PMID: 34324833 DOI: 10.1016/j.cub.2021.06.085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 06/01/2021] [Accepted: 06/28/2021] [Indexed: 11/15/2022]
Abstract
It is commonly acknowledged that memory is substantially improved when learning is distributed over time, an effect called the "spacing effect". So far it has not been studied how spaced learning affects the neuronal ensembles presumably underlying memory. In the present study, we investigate whether trial spacing increases the stability or size of neuronal ensembles. Mice were trained in the "everyday memory" task, an appetitive, naturalistic, delayed matching-to-place task. Spacing trials by 60 min produced more robust memories than training with shorter or longer intervals. c-Fos labeling and chemogenetic inactivation established the involvement of the dorsomedial prefrontal cortex (dmPFC) in successful memory storage. In vivo calcium imaging of excitatory dmPFC neurons revealed that longer trial spacing increased the similarity of the population activity pattern on subsequent encoding trials and upon retrieval. Conversely, trial spacing did not affect the size of the total neuronal ensemble or the size of subpopulations dedicated to specific task-related behaviors and events. Thus, spaced learning promotes reactivation of prefrontal neuronal ensembles processing episodic-like memories.
Collapse
Affiliation(s)
- Annet Glas
- Max Planck Institute of Neurobiology, Am Klopferspitz 18, 82152 Martinsried, Germany; Graduate School of Systemic Neurosciences, Ludwig-Maximilians-Universität München, Großhaderner Straße 2, 82152 Martinsried, Germany
| | - Mark Hübener
- Max Planck Institute of Neurobiology, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Tobias Bonhoeffer
- Max Planck Institute of Neurobiology, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Pieter M Goltstein
- Max Planck Institute of Neurobiology, Am Klopferspitz 18, 82152 Martinsried, Germany.
| |
Collapse
|
62
|
Weiss JT, Donlea JM. Sleep deprivation results in diverse patterns of synaptic scaling across the Drosophila mushroom bodies. Curr Biol 2021; 31:3248-3261.e3. [PMID: 34107302 PMCID: PMC8355077 DOI: 10.1016/j.cub.2021.05.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 03/22/2021] [Accepted: 05/11/2021] [Indexed: 11/19/2022]
Abstract
Sleep is essential for a variety of plastic processes, including learning and memory. However, the consequences of insufficient sleep on circuit connectivity remain poorly understood. To better appreciate the effects of sleep loss on synaptic connectivity across a memory-encoding circuit, we examined changes in the distribution of synaptic markers in the Drosophila mushroom body (MB). Protein-trap tags for active zone components indicate that recent sleep time is inversely correlated with Bruchpilot (BRP) abundance in the MB lobes; sleep loss elevates BRP while sleep induction reduces BRP across the MB. Overnight sleep deprivation also elevated levels of dSyd-1 and Cacophony, but not other pre-synaptic proteins. Cell-type-specific genetic reporters show that MB-intrinsic Kenyon cells (KCs) exhibit increased pre-synaptic BRP throughout the axonal lobes after sleep deprivation; similar increases were not detected in projections from large interneurons or dopaminergic neurons that innervate the MB. These results indicate that pre-synaptic plasticity in KCs is responsible for elevated levels of BRP in the MB lobes of sleep-deprived flies. Because KCs provide synaptic inputs to several classes of post-synaptic partners, we next used a fluorescent reporter for synaptic contacts to test whether each class of KC output connections is scaled uniformly by sleep loss. The KC output synapses that we observed here can be divided into three classes: KCs to MB interneurons; KCs to dopaminergic neurons; and KCs to MB output neurons. No single class showed uniform scaling across each constituent member, indicating that different rules may govern plasticity during sleep loss across cell types.
Collapse
Affiliation(s)
- Jacqueline T Weiss
- Department of Neurobiology, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095, USA; Neuroscience Interdepartmental Program, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Jeffrey M Donlea
- Department of Neurobiology, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095, USA.
| |
Collapse
|
63
|
Bennett JEM, Philippides A, Nowotny T. Learning with reinforcement prediction errors in a model of the Drosophila mushroom body. Nat Commun 2021; 12:2569. [PMID: 33963189 PMCID: PMC8105414 DOI: 10.1038/s41467-021-22592-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 03/16/2021] [Indexed: 02/03/2023] Open
Abstract
Effective decision making in a changing environment demands that accurate predictions are learned about decision outcomes. In Drosophila, such learning is orchestrated in part by the mushroom body, where dopamine neurons signal reinforcing stimuli to modulate plasticity presynaptic to mushroom body output neurons. Building on previous mushroom body models, in which dopamine neurons signal absolute reinforcement, we propose instead that dopamine neurons signal reinforcement prediction errors by utilising feedback reinforcement predictions from output neurons. We formulate plasticity rules that minimise prediction errors, verify that output neurons learn accurate reinforcement predictions in simulations, and postulate connectivity that explains more physiological observations than an experimentally constrained model. The constrained and augmented models reproduce a broad range of conditioning and blocking experiments, and we demonstrate that the absence of blocking does not imply the absence of prediction error dependent learning. Our results provide five predictions that can be tested using established experimental methods.
Collapse
Affiliation(s)
- James E. M. Bennett
- grid.12082.390000 0004 1936 7590Department of Informatics, University of Sussex, Brighton, UK
| | - Andrew Philippides
- grid.12082.390000 0004 1936 7590Department of Informatics, University of Sussex, Brighton, UK
| | - Thomas Nowotny
- grid.12082.390000 0004 1936 7590Department of Informatics, University of Sussex, Brighton, UK
| |
Collapse
|
64
|
Springer M, Nawrot MP. A Mechanistic Model for Reward Prediction and Extinction Learning in the Fruit Fly. eNeuro 2021; 8:ENEURO.0549-20.2021. [PMID: 33785523 PMCID: PMC8211469 DOI: 10.1523/eneuro.0549-20.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 03/15/2021] [Accepted: 03/18/2021] [Indexed: 01/08/2023] Open
Abstract
Extinction learning, the ability to update previously learned information by integrating novel contradictory information, is of high clinical relevance for therapeutic approaches to the modulation of maladaptive memories. Insect models have been instrumental in uncovering fundamental processes of memory formation and memory update. Recent experimental results in Drosophila melanogaster suggest that, after the behavioral extinction of a memory, two parallel but opposing memory traces coexist, residing at different sites within the mushroom body (MB). Here, we propose a minimalistic circuit model of the Drosophila MB that supports classical appetitive and aversive conditioning and memory extinction. The model is tailored to the existing anatomic data and involves two circuit motives of central functional importance. It employs plastic synaptic connections between Kenyon cells (KCs) and MB output neurons (MBONs) in separate and mutually inhibiting appetitive and aversive learning pathways. Recurrent modulation of plasticity through projections from MBONs to reinforcement-mediating dopaminergic neurons (DAN) implements a simple reward prediction mechanism. A distinct set of four MBONs encodes odor valence and predicts behavioral model output. Subjecting our model to learning and extinction protocols reproduced experimental results from recent behavioral and imaging studies. Simulating the experimental blocking of synaptic output of individual neurons or neuron groups in the model circuit confirmed experimental results and allowed formulation of testable predictions. In the temporal domain, our model achieves rapid learning with a step-like increase in the encoded odor value after a single pairing of the conditioned stimulus (CS) with a reward or punishment, facilitating single-trial learning.
Collapse
Affiliation(s)
- Magdalena Springer
- Computational Systems Neuroscience, Institute of Zoology, University of Cologne, Biocenter, Cologne 50674, Germany
| | - Martin Paul Nawrot
- Computational Systems Neuroscience, Institute of Zoology, University of Cologne, Biocenter, Cologne 50674, Germany
| |
Collapse
|
65
|
Mozolewski P, Jeziorek M, Schuster CM, Bading H, Frost B, Dobrowolski R. The role of nuclear Ca2+ in maintaining neuronal homeostasis and brain health. J Cell Sci 2021; 134:jcs254904. [PMID: 33912918 PMCID: PMC8084578 DOI: 10.1242/jcs.254904] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Nuclear Ca2+ has emerged as one of the most potent mediators of the dialogue between neuronal synapses and the nucleus that regulates heterochromatin states, transcription factor activity, nuclear morphology and neuronal gene expression induced by synaptic activity. Recent studies underline the importance of nuclear Ca2+ signaling in long-lasting, activity-induced adaptation and maintenance of proper brain function. Diverse forms of neuroadaptation require transient nuclear Ca2+ signaling and cyclic AMP-responsive element-binding protein (CREB1, referred to here as CREB) as its prime target, which works as a tunable switch to drive and modulate specific gene expression profiles associated with memory, pain, addiction and neuroprotection. Furthermore, a reduction of nuclear Ca2+ levels has been shown to be neurotoxic and a causal factor driving the progression of neurodegenerative disorders, as well as affecting neuronal autophagy. Because of its central role in the brain, deficits in nuclear Ca2+ signaling may underlie a continuous loss of neuroprotection in the aging brain, contributing to the pathophysiology of Alzheimer's disease. In this Review, we discuss the principles of the 'nuclear calcium hypothesis' in the context of human brain function and its role in controlling diverse forms of neuroadaptation and neuroprotection. Furthermore, we present the most relevant and promising perspectives for future studies.
Collapse
Affiliation(s)
- Pawel Mozolewski
- Department of Biological Sciences, Rutgers University, Newark, NJ 07102, USA
| | - Maciej Jeziorek
- Department of Biological Sciences, Rutgers University, Newark, NJ 07102, USA
| | - Christoph M. Schuster
- Department of Neurobiology, Interdisciplinary Center for Neurosciences (IZN), Heidelberg University, INF 345 and INF 366, 69120 Heidelberg, Germany
| | - Hilmar Bading
- Department of Neurobiology, Interdisciplinary Center for Neurosciences (IZN), Heidelberg University, INF 345 and INF 366, 69120 Heidelberg, Germany
| | - Bess Frost
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, University of Texas Health, San Antonio, San Antonio, TX 78229, USA
- Sam and Ann Barshop Institute for Longevity and Aging Studies, Department of Cell Systems and Anatomy, University of Texas Health, San Antonio, San Antonio, TX 78229, USA
| | - Radek Dobrowolski
- Department of Biological Sciences, Rutgers University, Newark, NJ 07102, USA
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, University of Texas Health, San Antonio, San Antonio, TX 78229, USA
| |
Collapse
|
66
|
Delahunt CB, Maia PD, Kutz JN. Built to Last: Functional and Structural Mechanisms in the Moth Olfactory Network Mitigate Effects of Neural Injury. Brain Sci 2021; 11:brainsci11040462. [PMID: 33916469 PMCID: PMC8067361 DOI: 10.3390/brainsci11040462] [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: 01/28/2021] [Revised: 03/18/2021] [Accepted: 03/24/2021] [Indexed: 11/16/2022] Open
Abstract
Most organisms suffer neuronal damage throughout their lives, which can impair performance of core behaviors. Their neural circuits need to maintain function despite injury, which in particular requires preserving key system outputs. In this work, we explore whether and how certain structural and functional neuronal network motifs act as injury mitigation mechanisms. Specifically, we examine how (i) Hebbian learning, (ii) high levels of noise, and (iii) parallel inhibitory and excitatory connections contribute to the robustness of the olfactory system in the Manduca sexta moth. We simulate injuries on a detailed computational model of the moth olfactory network calibrated to data. The injuries are modeled on focal axonal swellings, a ubiquitous form of axonal pathology observed in traumatic brain injuries and other brain disorders. Axonal swellings effectively compromise spike train propagation along the axon, reducing the effective neural firing rate delivered to downstream neurons. All three of the network motifs examined significantly mitigate the effects of injury on readout neurons, either by reducing injury’s impact on readout neuron responses or by restoring these responses to pre-injury levels. These motifs may thus be partially explained by their value as adaptive mechanisms to minimize the functional effects of neural injury. More generally, robustness to injury is a vital design principle to consider when analyzing neural systems.
Collapse
Affiliation(s)
- Charles B. Delahunt
- Department of Applied Mathematics, University of Washington, Seattle, WA 98195-3925, USA;
- Correspondence: (C.B.D.); (P.D.M.)
| | - Pedro D. Maia
- Department of Mathematics, University of Texas at Arlington, Arlington, TX 76019, USA
- Correspondence: (C.B.D.); (P.D.M.)
| | - J. Nathan Kutz
- Department of Applied Mathematics, University of Washington, Seattle, WA 98195-3925, USA;
| |
Collapse
|
67
|
Roselli C, Ramaswami M, Boto T, Cervantes-Sandoval I. The Making of Long-Lasting Memories: A Fruit Fly Perspective. Front Behav Neurosci 2021; 15:662129. [PMID: 33859556 PMCID: PMC8042140 DOI: 10.3389/fnbeh.2021.662129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 03/08/2021] [Indexed: 11/25/2022] Open
Abstract
Understanding the nature of the molecular mechanisms underlying memory formation, consolidation, and forgetting are some of the fascinating questions in modern neuroscience. The encoding, stabilization and elimination of memories, rely on the structural reorganization of synapses. These changes will enable the facilitation or depression of neural activity in response to the acquisition of new information. In other words, these changes affect the weight of specific nodes within a neural network. We know that these plastic reorganizations require de novo protein synthesis in the context of Long-term memory (LTM). This process depends on neural activity triggered by the learned experience. The use of model organisms like Drosophila melanogaster has been proven essential for advancing our knowledge in the field of neuroscience. Flies offer an optimal combination of a more straightforward nervous system, composed of a limited number of cells, and while still displaying complex behaviors. Studies in Drosophila neuroscience, which expanded over several decades, have been critical for understanding the cellular and molecular mechanisms leading to the synaptic and behavioral plasticity occurring in the context of learning and memory. This is possible thanks to sophisticated technical approaches that enable precise control of gene expression in the fruit fly as well as neural manipulation, like chemogenetics, thermogenetics, or optogenetics. The search for the identity of genes expressed as a result of memory acquisition has been an active interest since the origins of behavioral genetics. From screenings of more or less specific candidates to broader studies based on transcriptome analysis, our understanding of the genetic control behind LTM has expanded exponentially in the past years. Here we review recent literature regarding how the formation of memories induces a rapid, extensive and, in many cases, transient wave of transcriptional activity. After a consolidation period, transcriptome changes seem more stable and likely represent the synthesis of new proteins. The complexity of the circuitry involved in memory formation and consolidation is such that there are localized changes in neural activity, both regarding temporal dynamics and the nature of neurons and subcellular locations affected, hence inducing specific temporal and localized changes in protein expression. Different types of neurons are recruited at different times into memory traces. In LTM, the synthesis of new proteins is required in specific subsets of cells. This de novo translation can take place in the somatic cytoplasm and/or locally in distinct zones of compartmentalized synaptic activity, depending on the nature of the proteins and the plasticity-inducing processes that occur. We will also review recent advances in understanding how localized changes are confined to the relevant synapse. These recent studies have led to exciting discoveries regarding proteins that were not previously involved in learning and memory processes. This invaluable information will lead to future functional studies on the roles that hundreds of new molecular actors play in modulating neural activity.
Collapse
Affiliation(s)
- Camilla Roselli
- Trinity College Institute of Neuroscience, School of Genetics and Microbiology, Smurfit Institute of Genetics and School of Natural Sciences, Trinity College Dublin, Dublin, Ireland
| | - Mani Ramaswami
- Trinity College Institute of Neuroscience, School of Genetics and Microbiology, Smurfit Institute of Genetics and School of Natural Sciences, Trinity College Dublin, Dublin, Ireland.,National Centre for Biological Sciences, TIFR, Bengaluru, India
| | - Tamara Boto
- Trinity College Institute of Neuroscience, Department of Physiology, School of Medicine, Trinity College Dublin, Dublin, Ireland
| | - Isaac Cervantes-Sandoval
- Department of Biology, Georgetown University, Washington, DC, United States.,Interdisciplinary Program in Neuroscience, Georgetown University, Washington, DC, United States
| |
Collapse
|
68
|
Wong JYH, Wan BA, Bland T, Montagnese M, McLachlan AD, O'Kane CJ, Zhang SW, Masuda-Nakagawa LM. Octopaminergic neurons have multiple targets in Drosophila larval mushroom body calyx and can modulate behavioral odor discrimination. ACTA ACUST UNITED AC 2021; 28:53-71. [PMID: 33452115 PMCID: PMC7812863 DOI: 10.1101/lm.052159.120] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 10/30/2020] [Indexed: 12/17/2022]
Abstract
Discrimination of sensory signals is essential for an organism to form and retrieve memories of relevance in a given behavioral context. Sensory representations are modified dynamically by changes in behavioral state, facilitating context-dependent selection of behavior, through signals carried by noradrenergic input in mammals, or octopamine (OA) in insects. To understand the circuit mechanisms of this signaling, we characterized the function of two OA neurons, sVUM1 neurons, that originate in the subesophageal zone (SEZ) and target the input region of the memory center, the mushroom body (MB) calyx, in larval Drosophila. We found that sVUM1 neurons target multiple neurons, including olfactory projection neurons (PNs), the inhibitory neuron APL, and a pair of extrinsic output neurons, but relatively few mushroom body intrinsic neurons, Kenyon cells. PN terminals carried the OA receptor Oamb, a Drosophila α1-adrenergic receptor ortholog. Using an odor discrimination learning paradigm, we showed that optogenetic activation of OA neurons compromised discrimination of similar odors but not learning ability. Our results suggest that sVUM1 neurons modify odor representations via multiple extrinsic inputs at the sensory input area to the MB olfactory learning circuit.
Collapse
Affiliation(s)
- J Y Hilary Wong
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
| | - Bo Angela Wan
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
| | - Tom Bland
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
| | - Marcella Montagnese
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
| | - Alex D McLachlan
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
| | - Cahir J O'Kane
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
| | - Shuo Wei Zhang
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
| | | |
Collapse
|
69
|
Dvořáček J, Kodrík D. Drosophila reward system - A summary of current knowledge. Neurosci Biobehav Rev 2021; 123:301-319. [PMID: 33421541 DOI: 10.1016/j.neubiorev.2020.12.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 12/16/2020] [Accepted: 12/27/2020] [Indexed: 01/19/2023]
Abstract
The fruit fly Drosophila melanogaster brain is the most extensively investigated model of a reward system in insects. Drosophila can discriminate between rewarding and punishing environmental stimuli and consequently undergo associative learning. Functional models, especially those modelling mushroom bodies, are constantly being developed using newly discovered information, adding to the complexity of creating a simple model of the reward system. This review aims to clarify whether its reward system also includes a hedonic component. Neurochemical systems that mediate the 'wanting' component of reward in the Drosophila brain are well documented, however, the systems that mediate the pleasure component of reward in mammals, including those involving the endogenous opioid and endocannabinoid systems, are unlikely to be present in insects. The mushroom body components exhibit differential developmental age and different functional processes. We propose a hypothetical hierarchy of the levels of reinforcement processing in response to particular stimuli, and the parallel processes that take place concurrently. The possible presence of activity-silencing and meta-satiety inducing levels in Drosophila should be further investigated.
Collapse
Affiliation(s)
- Jiří Dvořáček
- Institute of Entomology, Biology Centre, CAS, and Faculty of Science, University of South Bohemia, Branišovská 31, 370 05 České Budějovice, Czech Republic.
| | - Dalibor Kodrík
- Institute of Entomology, Biology Centre, CAS, and Faculty of Science, University of South Bohemia, Branišovská 31, 370 05 České Budějovice, Czech Republic
| |
Collapse
|
70
|
Puñal VM, Ahmed M, Thornton-Kolbe EM, Clowney EJ. Untangling the wires: development of sparse, distributed connectivity in the mushroom body calyx. Cell Tissue Res 2021; 383:91-112. [PMID: 33404837 PMCID: PMC9835099 DOI: 10.1007/s00441-020-03386-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 12/07/2020] [Indexed: 01/16/2023]
Abstract
Appropriate perception and representation of sensory stimuli pose an everyday challenge to the brain. In order to represent the wide and unpredictable array of environmental stimuli, principle neurons of associative learning regions receive sparse, combinatorial sensory inputs. Despite the broad role of such networks in sensory neural circuits, the developmental mechanisms underlying their emergence are not well understood. As mammalian sensory coding regions are numerically complex and lack the accessibility of simpler invertebrate systems, we chose to focus this review on the numerically simpler, yet functionally similar, Drosophila mushroom body calyx. We bring together current knowledge about the cellular and molecular mechanisms orchestrating calyx development, in addition to drawing insights from literature regarding construction of sparse wiring in the mammalian cerebellum. From this, we formulate hypotheses to guide our future understanding of the development of this critical perceptual center.
Collapse
Affiliation(s)
- Vanessa M. Puñal
- Department of Molecular, Cellular & Developmental Biology, The University of Michigan, Ann Arbor, MI 48109, USA,Department of Molecular & Integrative Physiology, The University of Michigan, Ann Arbor, MI 48109, USA
| | - Maria Ahmed
- Department of Molecular, Cellular & Developmental Biology, The University of Michigan, Ann Arbor, MI 48109, USA
| | - Emma M. Thornton-Kolbe
- Department of Molecular, Cellular & Developmental Biology, The University of Michigan, Ann Arbor, MI 48109, USA,Neuroscience Graduate Program, The University of Michigan, Ann Arbor, MI 48109, USA
| | - E. Josephine Clowney
- Department of Molecular, Cellular & Developmental Biology, The University of Michigan, Ann Arbor, MI 48109, USA
| |
Collapse
|
71
|
Abstract
With less than a million neurons, the western honeybee Apis mellifera is capable of complex olfactory behaviors and provides an ideal model for investigating the neurophysiology of the olfactory circuit and the basis of olfactory perception and learning. Here, we review the most fundamental aspects of honeybee's olfaction: first, we discuss which odorants dominate its environment, and how bees use them to communicate and regulate colony homeostasis; then, we describe the neuroanatomy and the neurophysiology of the olfactory circuit; finally, we explore the cellular and molecular mechanisms leading to olfactory memory formation. The vastity of histological, neurophysiological, and behavioral data collected during the last century, together with new technological advancements, including genetic tools, confirm the honeybee as an attractive research model for understanding olfactory coding and learning.
Collapse
Affiliation(s)
- Marco Paoli
- Research Centre on Animal Cognition, Center for Integrative Biology, CNRS, University of Toulouse, 31062, Toulouse, France.
| | - Giovanni C Galizia
- Department of Neuroscience, University of Konstanz, 78457, Konstanz, Germany.
| |
Collapse
|
72
|
McManus J. Sparse Neural Representation of Odor Predicts Learning. JOURNAL OF UNDERGRADUATE NEUROSCIENCE EDUCATION : JUNE : A PUBLICATION OF FUN, FACULTY FOR UNDERGRADUATE NEUROSCIENCE 2020; 19:R1-R3. [PMID: 33880103 PMCID: PMC8040833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Revised: 04/24/2020] [Accepted: 05/24/2020] [Indexed: 06/12/2023]
Abstract
The way in which neurons encode information remains a hotly debated topic in neuroscience. Lin and colleagues in a 2014 article in the journal Nature Neuroscience demonstrate how sparse coding in the olfactory learning and memory center of Drosophila can influence learning behavior. Coding sparsity is the idea that only a small number of neurons in a network represent any given stimulus. Using neurogenetics, computational neuroscience, and cognitive approaches, they outline the discovery of an inhibitory feedback circuit responsible for differentiating the neuronal response to different odors. Manipulating this feedback circuit, they demonstrate how the sparseness in neural networks (how easily neurons are activated) can correspond to the ability to learn a sensory discrimination more easily. From a research perspective, this paper was important as it was the first causal demonstration of the role of sparseness in learning. From a teaching point of view, this paper is valuable because it is a simple but effective introduction to artificial neural network theory, where both the abstract theory and the importance of its application is apparent to those without a mathematical or computational background.
Collapse
Affiliation(s)
- James McManus
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, UK, KY16 9JP
| |
Collapse
|
73
|
Felsenberg J. Changing memories on the fly: the neural circuits of memory re-evaluation in Drosophila melanogaster. Curr Opin Neurobiol 2020; 67:190-198. [PMID: 33373859 DOI: 10.1016/j.conb.2020.12.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 12/03/2020] [Accepted: 12/07/2020] [Indexed: 11/30/2022]
Abstract
Associative learning leads to modifications in neural networks to assign valence to sensory cues. These changes not only allow the expression of learned behavior but also modulate subsequent learning events. In the brain of the adult fruit fly, Drosophila melanogaster, olfactory memories are established as dopamine-driven plasticity in the output of a highly recurrent network, the mushroom body. Recent findings have highlighted how these changes in the network can steer the strengthening, weakening and formation of parallel memories when flies are exposed to subsequent training trials, conflicting situations or the reversal of contingencies. Together, these processes provide an initial understanding of how learned information can be used to guide the re-evaluation of memories.
Collapse
|
74
|
Li F, Lindsey JW, Marin EC, Otto N, Dreher M, Dempsey G, Stark I, Bates AS, Pleijzier MW, Schlegel P, Nern A, Takemura SY, Eckstein N, Yang T, Francis A, Braun A, Parekh R, Costa M, Scheffer LK, Aso Y, Jefferis GSXE, Abbott LF, Litwin-Kumar A, Waddell S, Rubin GM. The connectome of the adult Drosophila mushroom body provides insights into function. eLife 2020; 9:e62576. [PMID: 33315010 PMCID: PMC7909955 DOI: 10.7554/elife.62576] [Citation(s) in RCA: 174] [Impact Index Per Article: 43.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 12/11/2020] [Indexed: 12/12/2022] Open
Abstract
Making inferences about the computations performed by neuronal circuits from synapse-level connectivity maps is an emerging opportunity in neuroscience. The mushroom body (MB) is well positioned for developing and testing such an approach due to its conserved neuronal architecture, recently completed dense connectome, and extensive prior experimental studies of its roles in learning, memory, and activity regulation. Here, we identify new components of the MB circuit in Drosophila, including extensive visual input and MB output neurons (MBONs) with direct connections to descending neurons. We find unexpected structure in sensory inputs, in the transfer of information about different sensory modalities to MBONs, and in the modulation of that transfer by dopaminergic neurons (DANs). We provide insights into the circuitry used to integrate MB outputs, connectivity between the MB and the central complex and inputs to DANs, including feedback from MBONs. Our results provide a foundation for further theoretical and experimental work.
Collapse
Affiliation(s)
- Feng Li
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Jack W Lindsey
- Department of Neuroscience, Columbia University, Zuckerman InstituteNew YorkUnited States
| | - Elizabeth C Marin
- Drosophila Connectomics Group, Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Nils Otto
- Drosophila Connectomics Group, Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Centre for Neural Circuits & Behaviour, University of OxfordOxfordUnited Kingdom
| | - Marisa Dreher
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Georgia Dempsey
- Drosophila Connectomics Group, Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Ildiko Stark
- Drosophila Connectomics Group, Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Alexander S Bates
- Neurobiology Division, MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | | | - Philipp Schlegel
- Drosophila Connectomics Group, Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Neurobiology Division, MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Aljoscha Nern
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Shin-ya Takemura
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Nils Eckstein
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Tansy Yang
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Audrey Francis
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Amalia Braun
- Drosophila Connectomics Group, Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Ruchi Parekh
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Marta Costa
- Drosophila Connectomics Group, Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Louis K Scheffer
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Yoshinori Aso
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Gregory SXE Jefferis
- Drosophila Connectomics Group, Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Neurobiology Division, MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Larry F Abbott
- Department of Neuroscience, Columbia University, Zuckerman InstituteNew YorkUnited States
| | - Ashok Litwin-Kumar
- Department of Neuroscience, Columbia University, Zuckerman InstituteNew YorkUnited States
| | - Scott Waddell
- Centre for Neural Circuits & Behaviour, University of OxfordOxfordUnited Kingdom
| | - Gerald M Rubin
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| |
Collapse
|
75
|
Durrieu M, Wystrach A, Arrufat P, Giurfa M, Isabel G. Fruit flies can learn non-elemental olfactory discriminations. Proc Biol Sci 2020; 287:20201234. [PMID: 33171086 PMCID: PMC7735272 DOI: 10.1098/rspb.2020.1234] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 10/19/2020] [Indexed: 12/25/2022] Open
Abstract
Associative learning allows animals to establish links between stimuli based on their concomitance. In the case of Pavlovian conditioning, a single stimulus A (the conditional stimulus, CS) is reinforced unambiguously with an unconditional stimulus (US) eliciting an innate response. This conditioning constitutes an 'elemental' association to elicit a learnt response from A+ without US presentation after learning. However, associative learning may involve a 'complex' CS composed of several components. In that case, the compound may predict a different outcome than the components taken separately, leading to ambiguity and requiring the animal to perform so-called non-elemental discrimination. Here, we focus on such a non-elemental task, the negative patterning (NP) problem, and provide the first evidence of NP solving in Drosophila. We show that Drosophila learn to discriminate a simple component (A or B) associated with electric shocks (+) from an odour mixture composed either partly (called 'feature-negative discrimination' A+ versus AB-) or entirely (called 'NP' A+B+ versus AB-) of the shock-associated components. Furthermore, we show that conditioning repetition results in a transition from an elemental to a configural representation of the mixture required to solve the NP task, highlighting the cognitive flexibility of Drosophila.
Collapse
Affiliation(s)
- Matthias Durrieu
- Research Centre on Animal Cognition, Centre for Integrative Biology, CNRS, University of Toulouse, 118 route de Narbonne, F-31062 Toulouse, France
| | - Antoine Wystrach
- Research Centre on Animal Cognition, Centre for Integrative Biology, CNRS, University of Toulouse, 118 route de Narbonne, F-31062 Toulouse, France
| | - Patrick Arrufat
- Research Centre on Animal Cognition, Centre for Integrative Biology, CNRS, University of Toulouse, 118 route de Narbonne, F-31062 Toulouse, France
| | - Martin Giurfa
- Research Centre on Animal Cognition, Centre for Integrative Biology, CNRS, University of Toulouse, 118 route de Narbonne, F-31062 Toulouse, France
- College of Animal Science (College of Bee Science), Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Institut Universitaire de France (IUF), Paris, France
| | - Guillaume Isabel
- Research Centre on Animal Cognition, Centre for Integrative Biology, CNRS, University of Toulouse, 118 route de Narbonne, F-31062 Toulouse, France
| |
Collapse
|
76
|
Rapp H, Nawrot MP. A spiking neural program for sensorimotor control during foraging in flying insects. Proc Natl Acad Sci U S A 2020; 117:28412-28421. [PMID: 33122439 PMCID: PMC7668073 DOI: 10.1073/pnas.2009821117] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Foraging is a vital behavioral task for living organisms. Behavioral strategies and abstract mathematical models thereof have been described in detail for various species. To explore the link between underlying neural circuits and computational principles, we present how a biologically detailed neural circuit model of the insect mushroom body implements sensory processing, learning, and motor control. We focus on cast and surge strategies employed by flying insects when foraging within turbulent odor plumes. Using a spike-based plasticity rule, the model rapidly learns to associate individual olfactory sensory cues paired with food in a classical conditioning paradigm. We show that, without retraining, the system dynamically recalls memories to detect relevant cues in complex sensory scenes. Accumulation of this sensory evidence on short time scales generates cast-and-surge motor commands. Our generic systems approach predicts that population sparseness facilitates learning, while temporal sparseness is required for dynamic memory recall and precise behavioral control. Our work successfully combines biological computational principles with spike-based machine learning. It shows how knowledge transfer from static to arbitrary complex dynamic conditions can be achieved by foraging insects and may serve as inspiration for agent-based machine learning.
Collapse
Affiliation(s)
- Hannes Rapp
- Computational Systems Neuroscience, Institute of Zoology, University of Cologne, Cologne 50674, Germany
| | - Martin Paul Nawrot
- Computational Systems Neuroscience, Institute of Zoology, University of Cologne, Cologne 50674, Germany
| |
Collapse
|
77
|
Zhao F, Zeng Y, Guo A, Su H, Xu B. A neural algorithm for Drosophila linear and nonlinear decision-making. Sci Rep 2020; 10:18660. [PMID: 33122701 PMCID: PMC7596070 DOI: 10.1038/s41598-020-75628-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 10/16/2020] [Indexed: 11/15/2022] Open
Abstract
It has been evidenced that vision-based decision-making in Drosophila consists of both simple perceptual (linear) decision and value-based (non-linear) decision. This paper proposes a general computational spiking neural network (SNN) model to explore how different brain areas are connected contributing to Drosophila linear and nonlinear decision-making behavior. First, our SNN model could successfully describe all the experimental findings in fly visual reinforcement learning and action selection among multiple conflicting choices as well. Second, our computational modeling shows that dopaminergic neuron-GABAergic neuron-mushroom body (DA-GABA-MB) works in a recurrent loop providing a key circuit for gain and gating mechanism of nonlinear decision making. Compared with existing models, our model shows more biologically plausible on the network design and working mechanism, and could amplify the small differences between two conflicting cues more clearly. Finally, based on the proposed model, the UAV could quickly learn to make clear-cut decisions among multiple visual choices and flexible reversal learning resembling to real fly. Compared with linear and uniform decision-making methods, the DA-GABA-MB mechanism helps UAV complete the decision-making task with fewer steps.
Collapse
Affiliation(s)
- Feifei Zhao
- Research Center for Brain-inspired Intelligence, Institute of Automation, Chinese Academy of Sciences, Beijing, 100190, China
| | - Yi Zeng
- Research Center for Brain-inspired Intelligence, Institute of Automation, Chinese Academy of Sciences, Beijing, 100190, China. .,Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China. .,National Laboratory of Pattern Recognition, Institute of Automation, Chinese Academy of Sciences, Beijing, 100190, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Aike Guo
- Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China. .,Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China. .,State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China. .,Shanghai Institute of Microsystem and Information Technology, Shanghai, 200050, China.
| | - Haifeng Su
- Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China.,Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China.,Laboratory of Molecular Neural Biology, School of Life Sciences, Shanghai University, Shanghai, 200444, China
| | - Bo Xu
- Research Center for Brain-inspired Intelligence, Institute of Automation, Chinese Academy of Sciences, Beijing, 100190, China.,Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| |
Collapse
|
78
|
Endo K, Tsuchimoto Y, Kazama H. Synthesis of Conserved Odor Object Representations in a Random, Divergent-Convergent Network. Neuron 2020; 108:367-381.e5. [PMID: 32814018 DOI: 10.1016/j.neuron.2020.07.029] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 03/10/2020] [Accepted: 07/24/2020] [Indexed: 01/09/2023]
Abstract
Animals are capable of recognizing mixtures and groups of odors as a unitary object. However, how odor object representations are generated in the brain remains elusive. Here, we investigate sensory transformation between the primary olfactory center and its downstream region, the mushroom body (MB), in Drosophila and show that clustered representations for mixtures and groups of odors emerge in the MB at the population and single-cell levels. Decoding analyses demonstrate that neurons selective for mixtures and groups enhance odor generalization. Responses of these neurons and those selective for individual odors all emerge in an experimentally well-constrained model implementing divergent-convergent, random connectivity between the primary center and the MB. Furthermore, we found that relative odor representations are conserved across animals despite this random connectivity. Our results show that the generation of distinct representations for individual odors and groups and mixtures of odors in the MB can be understood in a unified computational and mechanistic framework.
Collapse
Affiliation(s)
- Keita Endo
- RIKEN Center for Brain Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan; RIKEN CBS-KAO Collaboration Center, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Yoshiko Tsuchimoto
- RIKEN Center for Brain Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Hokto Kazama
- RIKEN Center for Brain Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan; RIKEN CBS-KAO Collaboration Center, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan; Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan.
| |
Collapse
|
79
|
Muscarinic Modulation of Antennal Lobe GABAergic Local Neurons Shapes Odor Coding and Behavior. Cell Rep 2020; 29:3253-3265.e4. [PMID: 31801087 PMCID: PMC6900217 DOI: 10.1016/j.celrep.2019.10.125] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 09/18/2019] [Accepted: 10/29/2019] [Indexed: 11/21/2022] Open
Abstract
In the antennal lobe (AL), the first olfactory relay of Drosophila, excitatory neurons are predominantly cholinergic. Ionotropic nicotinic receptors play a vital role in the effects of acetylcholine in the AL. However, the AL also has a high expression level of metabotropic muscarinic acetylcholine receptors type A (mAChRs-A). Nevertheless, the neurons expressing them and their role in the AL are unknown. Elucidating their function may reveal principles in olfactory modulation. Here, we show that mAChRs-A shape AL output and affect behavior. We localized mAChRs-A effects to a sub-population of GABAergic local neurons (iLNs), where they play a dual role: direct excitation of iLNs and stabilization of the synapse between receptor neurons and iLNs, which undergoes strong short-term depression. Our results reveal modulatory functions of the AL main excitatory neurotransmitter. Striking similarities to the mammalian olfactory system predict that mammalian glutamatergic metabotropic receptors could be associated with similar modulations.
Collapse
|
80
|
Amin H, Apostolopoulou AA, Suárez-Grimalt R, Vrontou E, Lin AC. Localized inhibition in the Drosophila mushroom body. eLife 2020; 9:56954. [PMID: 32955437 PMCID: PMC7541083 DOI: 10.7554/elife.56954] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 08/02/2020] [Indexed: 12/12/2022] Open
Abstract
Many neurons show compartmentalized activity, in which activity does not spread readily across the cell, allowing input and output to occur locally. However, the functional implications of compartmentalized activity for the wider neural circuit are often unclear. We addressed this problem in the Drosophila mushroom body, whose principal neurons, Kenyon cells, receive feedback inhibition from a non-spiking interneuron called the anterior paired lateral (APL) neuron. We used local stimulation and volumetric calcium imaging to show that APL inhibits Kenyon cells’ dendrites and axons, and that both activity in APL and APL’s inhibitory effect on Kenyon cells are spatially localized (the latter somewhat less so), allowing APL to differentially inhibit different mushroom body compartments. Applying these results to the Drosophila hemibrain connectome predicts that individual Kenyon cells inhibit themselves via APL more strongly than they inhibit other individual Kenyon cells. These findings reveal how cellular physiology and detailed network anatomy can combine to influence circuit function.
Collapse
Affiliation(s)
- Hoger Amin
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom.,Neuroscience Institute, University of Sheffield, Sheffield, United Kingdom
| | - Anthi A Apostolopoulou
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom.,Neuroscience Institute, University of Sheffield, Sheffield, United Kingdom
| | - Raquel Suárez-Grimalt
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Eleftheria Vrontou
- Centre for Neural Circuits and Behaviour, University of Oxford, Oxford, United Kingdom
| | - Andrew C Lin
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom.,Neuroscience Institute, University of Sheffield, Sheffield, United Kingdom
| |
Collapse
|
81
|
Scheffer LK, Xu CS, Januszewski M, Lu Z, Takemura SY, Hayworth KJ, Huang GB, Shinomiya K, Maitlin-Shepard J, Berg S, Clements J, Hubbard PM, Katz WT, Umayam L, Zhao T, Ackerman D, Blakely T, Bogovic J, Dolafi T, Kainmueller D, Kawase T, Khairy KA, Leavitt L, Li PH, Lindsey L, Neubarth N, Olbris DJ, Otsuna H, Trautman ET, Ito M, Bates AS, Goldammer J, Wolff T, Svirskas R, Schlegel P, Neace E, Knecht CJ, Alvarado CX, Bailey DA, Ballinger S, Borycz JA, Canino BS, Cheatham N, Cook M, Dreher M, Duclos O, Eubanks B, Fairbanks K, Finley S, Forknall N, Francis A, Hopkins GP, Joyce EM, Kim S, Kirk NA, Kovalyak J, Lauchie SA, Lohff A, Maldonado C, Manley EA, McLin S, Mooney C, Ndama M, Ogundeyi O, Okeoma N, Ordish C, Padilla N, Patrick CM, Paterson T, Phillips EE, Phillips EM, Rampally N, Ribeiro C, Robertson MK, Rymer JT, Ryan SM, Sammons M, Scott AK, Scott AL, Shinomiya A, Smith C, Smith K, Smith NL, Sobeski MA, Suleiman A, Swift J, Takemura S, Talebi I, Tarnogorska D, Tenshaw E, Tokhi T, Walsh JJ, Yang T, Horne JA, Li F, Parekh R, Rivlin PK, Jayaraman V, Costa M, Jefferis GSXE, Ito K, Saalfeld S, George R, Meinertzhagen IA, Rubin GM, Hess HF, Jain V, Plaza SM. A connectome and analysis of the adult Drosophila central brain. eLife 2020; 9:e57443. [PMID: 32880371 PMCID: PMC7546738 DOI: 10.7554/elife.57443] [Citation(s) in RCA: 440] [Impact Index Per Article: 110.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 09/01/2020] [Indexed: 12/26/2022] Open
Abstract
The neural circuits responsible for animal behavior remain largely unknown. We summarize new methods and present the circuitry of a large fraction of the brain of the fruit fly Drosophila melanogaster. Improved methods include new procedures to prepare, image, align, segment, find synapses in, and proofread such large data sets. We define cell types, refine computational compartments, and provide an exhaustive atlas of cell examples and types, many of them novel. We provide detailed circuits consisting of neurons and their chemical synapses for most of the central brain. We make the data public and simplify access, reducing the effort needed to answer circuit questions, and provide procedures linking the neurons defined by our analysis with genetic reagents. Biologically, we examine distributions of connection strengths, neural motifs on different scales, electrical consequences of compartmentalization, and evidence that maximizing packing density is an important criterion in the evolution of the fly's brain.
Collapse
Affiliation(s)
- Louis K Scheffer
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - C Shan Xu
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | | | - Zhiyuan Lu
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
- Life Sciences Centre, Dalhousie UniversityHalifaxCanada
| | - Shin-ya Takemura
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Kenneth J Hayworth
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Gary B Huang
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Kazunori Shinomiya
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | | | - Stuart Berg
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Jody Clements
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Philip M Hubbard
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - William T Katz
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Lowell Umayam
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Ting Zhao
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - David Ackerman
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | | | - John Bogovic
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Tom Dolafi
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Dagmar Kainmueller
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Takashi Kawase
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Khaled A Khairy
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | | | - Peter H Li
- Google ResearchMountain ViewUnited States
| | | | - Nicole Neubarth
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Donald J Olbris
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Hideo Otsuna
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Eric T Trautman
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Masayoshi Ito
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
- Institute for Quantitative Biosciences, University of TokyoTokyoJapan
| | | | - Jens Goldammer
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
- Institute of Zoology, Biocenter Cologne, University of CologneCologneGermany
| | - Tanya Wolff
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Robert Svirskas
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | | | - Erika Neace
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | | | - Chelsea X Alvarado
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Dennis A Bailey
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Samantha Ballinger
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | | | - Brandon S Canino
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Natasha Cheatham
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Michael Cook
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Marisa Dreher
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Octave Duclos
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Bryon Eubanks
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Kelli Fairbanks
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Samantha Finley
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Nora Forknall
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Audrey Francis
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | | | - Emily M Joyce
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - SungJin Kim
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Nicole A Kirk
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Julie Kovalyak
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Shirley A Lauchie
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Alanna Lohff
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Charli Maldonado
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Emily A Manley
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Sari McLin
- Life Sciences Centre, Dalhousie UniversityHalifaxCanada
| | - Caroline Mooney
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Miatta Ndama
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Omotara Ogundeyi
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Nneoma Okeoma
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Christopher Ordish
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Nicholas Padilla
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | | | - Tyler Paterson
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Elliott E Phillips
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Emily M Phillips
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Neha Rampally
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Caitlin Ribeiro
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | | | - Jon Thomson Rymer
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Sean M Ryan
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Megan Sammons
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Anne K Scott
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Ashley L Scott
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Aya Shinomiya
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Claire Smith
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Kelsey Smith
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Natalie L Smith
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Margaret A Sobeski
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Alia Suleiman
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Jackie Swift
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Satoko Takemura
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Iris Talebi
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | | | - Emily Tenshaw
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Temour Tokhi
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - John J Walsh
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Tansy Yang
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | | | - Feng Li
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Ruchi Parekh
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Patricia K Rivlin
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Vivek Jayaraman
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Marta Costa
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Gregory SXE Jefferis
- MRC Laboratory of Molecular BiologyCambridgeUnited States
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
| | - Kei Ito
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
- Institute for Quantitative Biosciences, University of TokyoTokyoJapan
- Institute of Zoology, Biocenter Cologne, University of CologneCologneGermany
| | - Stephan Saalfeld
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Reed George
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Ian A Meinertzhagen
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
- Life Sciences Centre, Dalhousie UniversityHalifaxCanada
| | - Gerald M Rubin
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Harald F Hess
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Viren Jain
- Google Research, Google LLCZurichSwitzerland
| | - Stephen M Plaza
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| |
Collapse
|
82
|
A biologically plausible network model for pattern storage and recall inspired by Dentate Gyrus. Neural Comput Appl 2020. [DOI: 10.1007/s00521-019-04670-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
83
|
Bates AS, Schlegel P, Roberts RJV, Drummond N, Tamimi IFM, Turnbull R, Zhao X, Marin EC, Popovici PD, Dhawan S, Jamasb A, Javier A, Serratosa Capdevila L, Li F, Rubin GM, Waddell S, Bock DD, Costa M, Jefferis GSXE. Complete Connectomic Reconstruction of Olfactory Projection Neurons in the Fly Brain. Curr Biol 2020; 30:3183-3199.e6. [PMID: 32619485 PMCID: PMC7443706 DOI: 10.1016/j.cub.2020.06.042] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 05/07/2020] [Accepted: 06/12/2020] [Indexed: 12/21/2022]
Abstract
Nervous systems contain sensory neurons, local neurons, projection neurons, and motor neurons. To understand how these building blocks form whole circuits, we must distil these broad classes into neuronal cell types and describe their network connectivity. Using an electron micrograph dataset for an entire Drosophila melanogaster brain, we reconstruct the first complete inventory of olfactory projections connecting the antennal lobe, the insect analog of the mammalian olfactory bulb, to higher-order brain regions in an adult animal brain. We then connect this inventory to extant data in the literature, providing synaptic-resolution "holotypes" both for heavily investigated and previously unknown cell types. Projection neurons are approximately twice as numerous as reported by light level studies; cell types are stereotyped, but not identical, in cell and synapse numbers between brain hemispheres. The lateral horn, the insect analog of the mammalian cortical amygdala, is the main target for this olfactory information and has been shown to guide innate behavior. Here, we find new connectivity motifs, including axo-axonic connectivity between projection neurons, feedback, and lateral inhibition of these axons by a large population of neurons, and the convergence of different inputs, including non-olfactory inputs and memory-related feedback onto third-order olfactory neurons. These features are less prominent in the mushroom body calyx, the insect analog of the mammalian piriform cortex and a center for associative memory. Our work provides a complete neuroanatomical platform for future studies of the adult Drosophila olfactory system.
Collapse
Affiliation(s)
- Alexander S Bates
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Philipp Schlegel
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK; Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | | | - Nikolas Drummond
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Imaan F M Tamimi
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Robert Turnbull
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Xincheng Zhao
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK; Department of Entomology, College of Plant Protection, Henan Agricultural University, Zhengzhou 450002, China
| | - Elizabeth C Marin
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Patricia D Popovici
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Serene Dhawan
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Arian Jamasb
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Alexandre Javier
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | | | - Feng Li
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Gerald M Rubin
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Scott Waddell
- Centre for Neural Circuits and Behaviour, The University of Oxford, Oxford OX1 3SR, UK
| | - Davi D Bock
- Department of Neurological Sciences, Larner College of Medicine, University of Vermont, VT 05405, USA
| | - Marta Costa
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Gregory S X E Jefferis
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK; Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK.
| |
Collapse
|
84
|
Mariano V, Achsel T, Bagni C, Kanellopoulos AK. Modelling Learning and Memory in Drosophila to Understand Intellectual Disabilities. Neuroscience 2020; 445:12-30. [PMID: 32730949 DOI: 10.1016/j.neuroscience.2020.07.034] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 07/19/2020] [Accepted: 07/20/2020] [Indexed: 12/24/2022]
Abstract
Neurodevelopmental disorders (NDDs) include a large number of conditions such as Fragile X syndrome, autism spectrum disorders and Down syndrome, among others. They are characterized by limitations in adaptive and social behaviors, as well as intellectual disability (ID). Whole-exome and whole-genome sequencing studies have highlighted a large number of NDD/ID risk genes. To dissect the genetic causes and underlying biological pathways, in vivo experimental validation of the effects of these mutations is needed. The fruit fly, Drosophila melanogaster, is an ideal model to study NDDs, with highly tractable genetics, combined with simple behavioral and circuit assays, permitting rapid medium-throughput screening of NDD/ID risk genes. Here, we review studies where the use of well-established assays to study mechanisms of learning and memory in Drosophila has permitted insights into molecular mechanisms underlying IDs. We discuss how technologies in the fly model, combined with a high degree of molecular and physiological conservation between flies and mammals, highlight the Drosophila system as an ideal model to study neurodevelopmental disorders, from genetics to behavior.
Collapse
Affiliation(s)
- Vittoria Mariano
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne 1005, Switzerland; Department of Human Genetics, KU Leuven, Leuven 3000, Belgium
| | - Tilmann Achsel
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne 1005, Switzerland
| | - Claudia Bagni
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne 1005, Switzerland; Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome 00133, Italy.
| | | |
Collapse
|
85
|
Pannunzi M, Nowotny T. Non-synaptic interactions between olfactory receptor neurons, a possible key feature of odor processing in flies.. [DOI: 10.1101/2020.07.23.217216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
AbstractWhen flies explore their environment, they encounter odors in complex, highly intermittent plumes. To navigate a plume and, for example, find food, they must solve several challenges, including reliably identifying mixtures of odorants and their intensities, and discriminating odorant mixtures emanating from a single source from odorants emitted from separate sources and just mixing in the air. Lateral inhibition in the antennal lobe is commonly understood to help solving these challenges. With a computational model of the Drosophila olfactory system, we analyze the utility of an alternative mechanism for solving them: Non-synaptic (“ephaptic”) interactions (NSIs) between olfactory receptor neurons that are stereotypically co-housed in the same sensilla.We found that NSIs improve mixture ratio detection and plume structure sensing and they do so more efficiently than the traditionally considered mechanism of lateral inhibition in the antennal lobe. However, we also found that NSIs decrease the dynamic range of co-housed ORNs, especially when they have similar sensitivity to an odorant. These results shed light, from a functional perspective, on the role of NSIs, which are normally avoided between neurons, for instance by myelination.Author summaryMyelin is important to isolate neurons and avoid disruptive electrical interference between them; it can be found in almost any neural assembly. However, there are a few exceptions to this rule and it remains unclear why. One particularly interesting case is the electrical interaction between olfactory sensory neurons co-housed in the sensilla of insects. Here, we created a computational model of the early stages of the Drosophila olfactory system and observed that the electrical interference between olfactory receptor neurons can be a useful trait that can help flies, and other insects, to navigate the complex plumes of odorants in their natural environment.With the model we were able to shed new light on the trade-off of adopting this mechanism: We found that the non-synaptic interactions (NSIs) improve both the identification of the concentration ratio in mixtures of odorants and the discrimination of odorant mixtures emanating from a single source from odorants emitted from separate sources – both highly advantageous. However, they also decrease the dynamic range of the olfactory sensory neurons – a clear disadvantage.
Collapse
|
86
|
Apostolopoulou AA, Lin AC. Mechanisms underlying homeostatic plasticity in the Drosophila mushroom body in vivo. Proc Natl Acad Sci U S A 2020; 117:16606-16615. [PMID: 32601210 PMCID: PMC7368247 DOI: 10.1073/pnas.1921294117] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Neural network function requires an appropriate balance of excitation and inhibition to be maintained by homeostatic plasticity. However, little is known about homeostatic mechanisms in the intact central brain in vivo. Here, we study homeostatic plasticity in the Drosophila mushroom body, where Kenyon cells receive feedforward excitation from olfactory projection neurons and feedback inhibition from the anterior paired lateral neuron (APL). We show that prolonged (4-d) artificial activation of the inhibitory APL causes increased Kenyon cell odor responses after the artificial inhibition is removed, suggesting that the mushroom body compensates for excess inhibition. In contrast, there is little compensation for lack of inhibition (blockade of APL). The compensation occurs through a combination of increased excitation of Kenyon cells and decreased activation of APL, with differing relative contributions for different Kenyon cell subtypes. Our findings establish the fly mushroom body as a model for homeostatic plasticity in vivo.
Collapse
Affiliation(s)
- Anthi A Apostolopoulou
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom
- Neuroscience Institute, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Andrew C Lin
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom;
- Neuroscience Institute, University of Sheffield, Sheffield S10 2TN, United Kingdom
| |
Collapse
|
87
|
Abstract
Habituation is a form of simple memory that suppresses neural activity in response to repeated, neutral stimuli. This process is critical in helping organisms guide attention toward the most salient and novel features in the environment. Here, we follow known circuit mechanisms in the fruit fly olfactory system to derive a simple algorithm for habituation. We show, both empirically and analytically, that this algorithm is able to filter out redundant information, enhance discrimination between odors that share a similar background, and improve detection of novel components in odor mixtures. Overall, we propose an algorithmic perspective on the biological mechanism of habituation and use this perspective to understand how sensory physiology can affect odor perception. Our framework may also help toward understanding the effects of habituation in other more sophisticated neural systems.
Collapse
|
88
|
Effect of Circuit Structure on Odor Representation in the Insect Olfactory System. eNeuro 2020; 7:ENEURO.0130-19.2020. [PMID: 32345734 PMCID: PMC7292731 DOI: 10.1523/eneuro.0130-19.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 02/10/2020] [Accepted: 02/23/2020] [Indexed: 11/30/2022] Open
Abstract
In neuroscience, the structure of a circuit has often been used to intuit function—an inversion of Louis Kahn’s famous dictum, “Form follows function” (Kristan and Katz, 2006). However, different brain networks may use different network architectures to solve the same problem. The olfactory circuits of two insects, the locust, Schistocerca americana, and the fruit fly, Drosophila melanogaster, serve the same function—to identify and discriminate odors. The neural circuitry that achieves this shows marked structural differences. Projection neurons (PNs) in the antennal lobe innervate Kenyon cells (KCs) of the mushroom body. In locust, each KC receives inputs from ∼50% of PNs, a scheme that maximizes the difference between inputs to any two of ∼50,000 KCs. In contrast, in Drosophila, this number is only 5% and appears suboptimal. Using a computational model of the olfactory system, we show that the activity of KCs is sufficiently high-dimensional that it can separate similar odors regardless of the divergence of PN–KC connections. However, when temporal patterning encodes odor attributes, dense connectivity outperforms sparse connections. Increased separability comes at the cost of reliability. The disadvantage of sparse connectivity can be mitigated by incorporating other aspects of circuit architecture seen in Drosophila. Our simulations predict that Drosophila and locust circuits lie at different ends of a continuum where the Drosophila gives up on the ability to resolve similar odors to generalize across varying environments, while the locust separates odor representations but risks misclassifying noisy variants of the same odor.
Collapse
|
89
|
A molecular odorant transduction model and the complexity of spatio-temporal encoding in the Drosophila antenna. PLoS Comput Biol 2020; 16:e1007751. [PMID: 32287275 PMCID: PMC7182276 DOI: 10.1371/journal.pcbi.1007751] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 04/24/2020] [Accepted: 02/27/2020] [Indexed: 12/20/2022] Open
Abstract
Over the past two decades, substantial amount of work has been conducted to characterize different odorant receptors, neuroanatomy and odorant response properties of the early olfactory system of Drosophila melanogaster. Yet many odorant receptors remain only partially characterized, and the odorant transduction process and the axon hillock spiking mechanism of the olfactory sensory neurons (OSNs) have yet to be fully determined. Identity and concentration, two key characteristics of the space of odorants, are encoded by the odorant transduction process. Detailed molecular models of the odorant transduction process are, however, scarce for fruit flies. To address these challenges we advance a comprehensive model of fruit fly OSNs as a cascade consisting of an odorant transduction process (OTP) and a biophysical spike generator (BSG). We model odorant identity and concentration using an odorant-receptor binding rate tensor, modulated by the odorant concentration profile, and an odorant-receptor dissociation rate tensor, and quantitatively describe the mechanics of the molecular ligand binding/dissociation of the OTP. We model the BSG as a Connor-Stevens point neuron. The resulting spatio-temporal encoding model of the Drosophila antenna provides a theoretical foundation for understanding the neural code of both odorant identity and odorant concentration and advances the state-of-the-art in a number of ways. First, it quantifies on the molecular level the spatio-temporal level of complexity of the transformation taking place in the antennae. The concentration-dependent spatio-temporal code at the output of the antenna circuits determines the level of complexity of olfactory processing in the downstream neuropils, such as odorant recognition and olfactory associative learning. Second, the model is biologically validated using multiple electrophysiological recordings. Third, the model demonstrates that the currently available data for odorant-receptor responses only enable the estimation of the affinity of the odorant-receptor pairs. The odorant-dissociation rate is only available for a few odorant-receptor pairs. Finally, our model calls for new experiments for massively identifying the odorant-receptor dissociation rates of relevance to flies. Identity and concentration, intrinsically embedded in the odorant space, are two key characteristics of olfactory coding that define the level of complexity of neural processing throughout the olfactory system in the fruit fly. In this paper we advance a theoretical foundation for understanding these two characteristics by quantifying mathematically the odorant space and devising a biophysical model of the olfactory sensory neurons (OSNs). To validate our modeling approach, we propose and apply an algorithm to estimate the affinity value and the dissociation rate, the two characteristics that define odorant identity, of multiple odorant-receptor pairs. We then evaluate our model with a multitude of odorant waveforms and demonstrate that the model output reproduces the temporal responses of OSNs obtained from in vivo electrophysiology recordings. Furthermore, we evaluate the model at the OSN population level and quantify on the molecular level the spatio-temporal level of complexity of the transformation taking place between the odorant space and the OSNs. The resulting concentration-dependent spatio-temporal code determines the level of complexity of the input space driving olfactory processing in the downstream neuropils. Lastly, our model demonstrates that the currently available data for OSN responses only enables estimation of affinity value. This calls for new experiments for massively identifying the odorant-receptor dissociation rates of relevance to flies.
Collapse
|
90
|
Modi MN, Shuai Y, Turner GC. The Drosophila Mushroom Body: From Architecture to Algorithm in a Learning Circuit. Annu Rev Neurosci 2020; 43:465-484. [PMID: 32283995 DOI: 10.1146/annurev-neuro-080317-0621333] [Citation(s) in RCA: 86] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The Drosophila brain contains a relatively simple circuit for forming Pavlovian associations, yet it achieves many operations common across memory systems. Recent advances have established a clear framework for Drosophila learning and revealed the following key operations: a) pattern separation, whereby dense combinatorial representations of odors are preprocessed to generate highly specific, nonoverlapping odor patterns used for learning; b) convergence, in which sensory information is funneled to a small set of output neurons that guide behavioral actions; c) plasticity, where changing the mapping of sensory input to behavioral output requires a strong reinforcement signal, which is also modulated by internal state and environmental context; and d) modularization, in which a memory consists of multiple parallel traces, which are distinct in stability and flexibility and exist in anatomically well-defined modules within the network. Cross-module interactions allow for higher-order effects where past experience influences future learning. Many of these operations have parallels with processes of memory formation and action selection in more complex brains.
Collapse
Affiliation(s)
- Mehrab N Modi
- Janelia Research Campus, Ashburn, Virginia 20147, USA;
| | - Yichun Shuai
- Janelia Research Campus, Ashburn, Virginia 20147, USA;
| | | |
Collapse
|
91
|
Betkiewicz R, Lindner B, Nawrot MP. Circuit and Cellular Mechanisms Facilitate the Transformation from Dense to Sparse Coding in the Insect Olfactory System. eNeuro 2020; 7:ENEURO.0305-18.2020. [PMID: 32132095 PMCID: PMC7294456 DOI: 10.1523/eneuro.0305-18.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2018] [Revised: 10/31/2019] [Accepted: 02/19/2020] [Indexed: 11/21/2022] Open
Abstract
Transformations between sensory representations are shaped by neural mechanisms at the cellular and the circuit level. In the insect olfactory system, the encoding of odor information undergoes a transition from a dense spatiotemporal population code in the antennal lobe to a sparse code in the mushroom body. However, the exact mechanisms shaping odor representations and their role in sensory processing are incompletely identified. Here, we investigate the transformation from dense to sparse odor representations in a spiking model of the insect olfactory system, focusing on two ubiquitous neural mechanisms: spike frequency adaptation at the cellular level and lateral inhibition at the circuit level. We find that cellular adaptation is essential for sparse representations in time (temporal sparseness), while lateral inhibition regulates sparseness in the neuronal space (population sparseness). The interplay of both mechanisms shapes spatiotemporal odor representations, which are optimized for the discrimination of odors during stimulus onset and offset. Response pattern correlation across different stimuli showed a nonmonotonic dependence on the strength of lateral inhibition with an optimum at intermediate levels, which is explained by two counteracting mechanisms. In addition, we find that odor identity is stored on a prolonged timescale in the adaptation levels but not in the spiking activity of the principal cells of the mushroom body, providing a testable hypothesis for the location of the so-called odor trace.
Collapse
Affiliation(s)
- Rinaldo Betkiewicz
- Bernstein Center for Computational Neuroscience Berlin, 10115 Berlin, Germany
- Computational Systems Neuroscience, Institute of Zoology, University of Cologne, 50674 Cologne, Germany
- Department of Physics, Humboldt University Berlin, 12489 Berlin, Germany
| | - Benjamin Lindner
- Bernstein Center for Computational Neuroscience Berlin, 10115 Berlin, Germany
- Department of Physics, Humboldt University Berlin, 12489 Berlin, Germany
| | - Martin P Nawrot
- Bernstein Center for Computational Neuroscience Berlin, 10115 Berlin, Germany
- Computational Systems Neuroscience, Institute of Zoology, University of Cologne, 50674 Cologne, Germany
| |
Collapse
|
92
|
Lerner H, Rozenfeld E, Rozenman B, Huetteroth W, Parnas M. Differential Role for a Defined Lateral Horn Neuron Subset in Naïve Odor Valence in Drosophila. Sci Rep 2020; 10:6147. [PMID: 32273557 PMCID: PMC7145822 DOI: 10.1038/s41598-020-63169-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 03/26/2020] [Indexed: 11/09/2022] Open
Abstract
Value coding of external stimuli in general, and odor valence in particular, is crucial for survival. In flies, odor valence is thought to be coded by two types of neurons: mushroom body output neurons (MBONs) and lateral horn (LH) neurons. MBONs are classified as neurons that promote either attraction or aversion, but not both, and they are dynamically activated by upstream neurons. This dynamic activation updates the valence values. In contrast, LH neurons receive scaled, but non-dynamic, input from their upstream neurons. It remains unclear how such a non-dynamic system generates differential valence values. Recently, PD2a1/b1 LH neurons were demonstrated to promote approach behavior at low odor concentration in starved flies. Here, we demonstrate that at high odor concentrations, these same neurons contribute to avoidance in satiated flies. The contribution of PD2a1/b1 LH neurons to aversion is context dependent. It is diminished in starved flies, although PD2a1/b1 neural activity remains unchanged, and at lower odor concentration. In addition, PD2a1/b1 aversive effect develops over time. Thus, our results indicate that, even though PD2a1/b1 LH neurons transmit hard-wired output, their effect on valence can change. Taken together, we suggest that the valence model described for MBONs does not hold for LH neurons.
Collapse
Affiliation(s)
- Hadas Lerner
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Eyal Rozenfeld
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel.,Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Bar Rozenman
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Wolf Huetteroth
- Institute for Biology, University of Leipzig, Talstraße 33, 04103, Leipzig, Germany
| | - Moshe Parnas
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel. .,Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 69978, Israel.
| |
Collapse
|
93
|
Bilz F, Geurten BRH, Hancock CE, Widmann A, Fiala A. Visualization of a Distributed Synaptic Memory Code in the Drosophila Brain. Neuron 2020; 106:963-976.e4. [PMID: 32268119 DOI: 10.1016/j.neuron.2020.03.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 11/19/2019] [Accepted: 03/13/2020] [Indexed: 10/24/2022]
Abstract
During associative conditioning, animals learn which sensory cues are predictive for positive or negative conditions. Because sensory cues are encoded by distributed neurons, one has to monitor plasticity across many synapses to capture how learned information is encoded. We analyzed synaptic boutons of Kenyon cells of the Drosophila mushroom body γ lobe, a brain structure that mediates olfactory learning. A fluorescent Ca2+ sensor was expressed in single Kenyon cells so that axonal boutons could be assigned to distinct cells and Ca2+ could be measured across many animals. Learning induced directed synaptic plasticity in specific compartments along the axons. Moreover, we show that odor-evoked Ca2+ dynamics across boutons decorrelate as a result of associative learning. Information theory indicates that learning renders the stimulus representation more distinct compared with naive stimuli. These data reveal that synaptic boutons rather than cells act as individually modifiable units, and coherence among them is a memory-encoding parameter.
Collapse
Affiliation(s)
- Florian Bilz
- Department of Molecular Neurobiology of Behavior, Johann-Friedrich-Blumenbach-Institute for Zoology and Anthropology, University of Göttingen, Julia-Lermontowa-Weg 3, 37077 Göttingen, Germany
| | - Bart R H Geurten
- Department of Cellular Neurobiology, Johann-Friedrich-Blumenbach-Institute for Zoology and Anthropology, University of Göttingen, Julia-Lermontowa-Weg 3, 37077 Göttingen, Germany
| | - Clare E Hancock
- Department of Molecular Neurobiology of Behavior, Johann-Friedrich-Blumenbach-Institute for Zoology and Anthropology, University of Göttingen, Julia-Lermontowa-Weg 3, 37077 Göttingen, Germany
| | - Annekathrin Widmann
- Department of Molecular Neurobiology of Behavior, Johann-Friedrich-Blumenbach-Institute for Zoology and Anthropology, University of Göttingen, Julia-Lermontowa-Weg 3, 37077 Göttingen, Germany
| | - André Fiala
- Department of Molecular Neurobiology of Behavior, Johann-Friedrich-Blumenbach-Institute for Zoology and Anthropology, University of Göttingen, Julia-Lermontowa-Weg 3, 37077 Göttingen, Germany.
| |
Collapse
|
94
|
Ray S, Aldworth ZN, Stopfer MA. Feedback inhibition and its control in an insect olfactory circuit. eLife 2020; 9:53281. [PMID: 32163034 PMCID: PMC7145415 DOI: 10.7554/elife.53281] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2019] [Accepted: 03/09/2020] [Indexed: 01/20/2023] Open
Abstract
Inhibitory neurons play critical roles in regulating and shaping olfactory responses in vertebrates and invertebrates. In insects, these roles are performed by relatively few neurons, which can be interrogated efficiently, revealing fundamental principles of olfactory coding. Here, with electrophysiological recordings from the locust and a large-scale biophysical model, we analyzed the properties and functions of GGN, a unique giant GABAergic neuron that plays a central role in structuring olfactory codes in the locust mushroom body. Our simulations suggest that depolarizing GGN at its input branch can globally inhibit KCs several hundred microns away. Our in vivorecordings show that GGN responds to odors with complex temporal patterns of depolarization and hyperpolarization that can vary with odors and across animals, leading our model to predict the existence of a yet-undiscovered olfactory pathway. Our analysis reveals basic new features of GGN and the olfactory network surrounding it.
Collapse
Affiliation(s)
- Subhasis Ray
- Section on Sensory Coding and Neural Ensembles, NICHD, NIH, Bethesda, United States
| | - Zane N Aldworth
- Section on Sensory Coding and Neural Ensembles, NICHD, NIH, Bethesda, United States
| | - Mark A Stopfer
- Section on Sensory Coding and Neural Ensembles, NICHD, NIH, Bethesda, United States
| |
Collapse
|
95
|
Multiple network properties overcome random connectivity to enable stereotypic sensory responses. Nat Commun 2020; 11:1023. [PMID: 32094345 PMCID: PMC7039968 DOI: 10.1038/s41467-020-14836-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 02/03/2020] [Indexed: 02/08/2023] Open
Abstract
Connections between neuronal populations may be genetically hardwired or random. In the insect olfactory system, projection neurons of the antennal lobe connect randomly to Kenyon cells of the mushroom body. Consequently, while the odor responses of the projection neurons are stereotyped across individuals, the responses of the Kenyon cells are variable. Surprisingly, downstream of Kenyon cells, mushroom body output neurons show stereotypy in their responses. We found that the stereotypy is enabled by the convergence of inputs from many Kenyon cells onto an output neuron, and does not require learning. The stereotypy emerges in the total response of the Kenyon cell population using multiple odor-specific features of the projection neuron responses, benefits from the nonlinearity in the transfer function, depends on the convergence:randomness ratio, and is constrained by sparseness. Together, our results reveal the fundamental mechanisms and constraints with which convergence enables stereotypy in sensory responses despite random connectivity.
Collapse
|
96
|
Braganza O, Mueller-Komorowska D, Kelly T, Beck H. Quantitative properties of a feedback circuit predict frequency-dependent pattern separation. eLife 2020; 9:53148. [PMID: 32077850 PMCID: PMC7032930 DOI: 10.7554/elife.53148] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 01/20/2020] [Indexed: 12/16/2022] Open
Abstract
Feedback inhibitory motifs are thought to be important for pattern separation across species. How feedback circuits may implement pattern separation of biologically plausible, temporally structured input in mammals is, however, poorly understood. We have quantitatively determined key properties of netfeedback inhibition in the mouse dentate gyrus, a region critically involved in pattern separation. Feedback inhibition is recruited steeply with a low dynamic range (0% to 4% of active GCs), and with a non-uniform spatial profile. Additionally, net feedback inhibition shows frequency-dependent facilitation, driven by strongly facilitating mossy fiber inputs. Computational analyses show a significant contribution of the feedback circuit to pattern separation of theta modulated inputs, even within individual theta cycles. Moreover, pattern separation was selectively boosted at gamma frequencies, in particular for highly similar inputs. This effect was highly robust, suggesting that frequency-dependent pattern separation is a key feature of the feedback inhibitory microcircuit. You can probably recall where you left your car this morning without too much trouble. But assuming you use the same busy parking lot every day, can you remember which space you parked in yesterday? Or the day before that? Most people find this difficult not because they cannot remember what happened two or three days ago, but because it requires distinguishing between very similar memories. The car, the parking lot, and the time of day were the same on each occasion. So how do you remember where you parked this morning? This ability to distinguish between memories of similar events depends on a brain region called the hippocampus. A subregion of the hippocampus called the dentate gyrus generates different patterns of activity in response to events that are similar but distinct. This process is called pattern separation, and it helps ensure that you do not look for your car in yesterday’s parking space. Pattern separation in the dentate gyrus is thought to involve a form of negative feedback called feedback inhibition, a phenomenon where the output of a process acts to limit or stop the same process. To test this idea, Braganza et al. studied feedback inhibition in the dentate gyrus of mice, before building a computer model simulating the inhibition process and supplying the model with two types of realistic input. The first consisted of low-frequency theta brainwaves, which occur, for instance, in the dentate gyrus when animals explore their environment. The second consisted of higher frequency gamma brainwaves, which occur, for example, when animals experience something new. Testing the model showed that feedback inhibition contributes to pattern separation with both theta and gamma inputs. However, pattern separation is stronger with gamma input. This suggests that high frequency brainwaves in the hippocampus could help animals distinguish new events from old ones by promoting pattern separation. Various brain disorders, including Alzheimer’s disease, schizophrenia and epilepsy, involve changes in the dentate gyrus and altered brain rhythms. The current findings could help reveal how these changes contribute to memory impairments and to a reduced ability to distinguish similar experiences.
Collapse
Affiliation(s)
- Oliver Braganza
- Institute for Experimental Epileptology and Cognition Research, University of Bonn, Bonn, Germany
| | - Daniel Mueller-Komorowska
- Institute for Experimental Epileptology and Cognition Research, University of Bonn, Bonn, Germany.,International Max Planck Research School for Brain and Behavior, University of Bonn, Bonn, Germany
| | - Tony Kelly
- Institute for Experimental Epileptology and Cognition Research, University of Bonn, Bonn, Germany
| | - Heinz Beck
- Institute for Experimental Epileptology and Cognition Research, University of Bonn, Bonn, Germany.,Deutsches Zentrum für Neurodegenerative Erkrankungen e.V., Bonn, Germany
| |
Collapse
|
97
|
Boto T, Stahl A, Tomchik SM. Cellular and circuit mechanisms of olfactory associative learning in Drosophila. J Neurogenet 2020; 34:36-46. [PMID: 32043414 DOI: 10.1080/01677063.2020.1715971] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recent years have witnessed significant progress in understanding how memories are encoded, from the molecular to the cellular and the circuit/systems levels. With a good compromise between brain complexity and behavioral sophistication, the fruit fly Drosophila melanogaster is one of the preeminent animal models of learning and memory. Here we review how memories are encoded in Drosophila, with a focus on short-term memory and an eye toward future directions. Forward genetic screens have revealed a large number of genes and transcripts necessary for learning and memory, some acting cell-autonomously. Further, the relative numerical simplicity of the fly brain has enabled the reverse engineering of learning circuits with remarkable precision, in some cases ascribing behavioral phenotypes to single neurons. Functional imaging and physiological studies have localized and parsed the plasticity that occurs during learning at some of the major loci. Connectomics projects are significantly expanding anatomical knowledge of the nervous system, filling out the roadmap for ongoing functional/physiological and behavioral studies, which are being accelerated by simultaneous tool development. These developments have provided unprecedented insight into the fundamental neural principles of learning, and lay the groundwork for deep understanding in the near future.
Collapse
Affiliation(s)
- Tamara Boto
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, USA
| | - Aaron Stahl
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, USA
| | - Seth M Tomchik
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, USA
| |
Collapse
|
98
|
Optimality of sparse olfactory representations is not affected by network plasticity. PLoS Comput Biol 2020; 16:e1007461. [PMID: 32012160 PMCID: PMC7028362 DOI: 10.1371/journal.pcbi.1007461] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2019] [Revised: 02/18/2020] [Accepted: 10/07/2019] [Indexed: 11/25/2022] Open
Abstract
The neural representation of a stimulus is repeatedly transformed as it moves from the sensory periphery to deeper layers of the nervous system. Sparsening transformations are thought to increase the separation between similar representations, encode stimuli with great specificity, maximize storage capacity of associative memories, and provide an energy efficient instantiation of information in neural circuits. In the insect olfactory system, odors are initially represented in the periphery as a combinatorial code with relatively simple temporal dynamics. Subsequently, in the antennal lobe this representation is transformed into a dense and complex spatiotemporal activity pattern. Next, in the mushroom body Kenyon cells (KCs), the representation is dramatically sparsened. Finally, in mushroom body output neurons (MBONs), the representation takes on a new dense spatiotemporal format. Here, we develop a computational model to simulate this chain of olfactory processing from the receptor neurons to MBONs. We demonstrate that representations of similar odorants are maximally separated, measured by the distance between the corresponding MBON activity vectors, when KC responses are sparse. Sparseness is maintained across variations in odor concentration by adjusting the feedback inhibition that KCs receive from an inhibitory neuron, the Giant GABAergic neuron. Different odor concentrations require different strength and timing of feedback inhibition for optimal processing. Importantly, as observed in vivo, the KC–MBON synapse is highly plastic, and, therefore, changes in synaptic strength after learning can change the balance of excitation and inhibition, potentially leading to changes in the distance between MBON activity vectors of two odorants for the same level of KC population sparseness. Thus, what is an optimal degree of sparseness before odor learning, could be rendered sub–optimal post learning. Here, we show, however, that synaptic weight changes caused by spike timing dependent plasticity increase the distance between the odor representations from the perspective of MBONs. A level of sparseness that was optimal before learning remains optimal post-learning. Kenyon cells (KCs) of the mushroom body represent odors as a sparse code. When viewed from the perspective of follower neurons, mushroom body output neurons (MBONs) reveal an optimal level of coding sparseness that maximally separates the representations of odors. However, the KC–MBON synapse is highly plastic and may be potentiated or depressed by odor–driven experience that could, in turn, disrupt the optimality formed by pre–synaptic circuits. Contrary to this expectation, we show that synaptic plasticity based on spike timing of pre- and postsynaptic neurons improves the ability of the system to distinguish between the representations of similar odors while preserving the optimality determined by pre–synaptic circuits.
Collapse
|
99
|
McCutcheon RA, Krystal JH, Howes OD. Dopamine and glutamate in schizophrenia: biology, symptoms and treatment. World Psychiatry 2020; 19:15-33. [PMID: 31922684 PMCID: PMC6953551 DOI: 10.1002/wps.20693] [Citation(s) in RCA: 278] [Impact Index Per Article: 69.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Glutamate and dopamine systems play distinct roles in terms of neuronal signalling, yet both have been proposed to contribute significantly to the pathophysiology of schizophrenia. In this paper we assess research that has implicated both systems in the aetiology of this disorder. We examine evidence from post-mortem, preclinical, pharmacological and in vivo neuroimaging studies. Pharmacological and preclinical studies implicate both systems, and in vivo imaging of the dopamine system has consistently identified elevated striatal dopamine synthesis and release capacity in schizophrenia. Imaging of the glutamate system and other aspects of research on the dopamine system have produced less consistent findings, potentially due to methodological limitations and the heterogeneity of the disorder. Converging evidence indicates that genetic and environmental risk factors for schizophrenia underlie disruption of glutamatergic and dopaminergic function. However, while genetic influences may directly underlie glutamatergic dysfunction, few genetic risk variants directly implicate the dopamine system, indicating that aberrant dopamine signalling is likely to be predominantly due to other factors. We discuss the neural circuits through which the two systems interact, and how their disruption may cause psychotic symptoms. We also discuss mechanisms through which existing treatments operate, and how recent research has highlighted opportunities for the development of novel pharmacological therapies. Finally, we consider outstanding questions for the field, including what remains unknown regarding the nature of glutamate and dopamine function in schizophrenia, and what needs to be achieved to make progress in developing new treatments.
Collapse
Affiliation(s)
- Robert A McCutcheon
- Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- MRC London Institute of Medical Sciences, Imperial College London, Hammersmith Hospital, London, UK
- South London and Maudsley Foundation NHS Trust, Maudsley Hospital, London, UK
| | - John H Krystal
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, CT, USA
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
- VA National Center for PTSD, VA Connecticut Healthcare System, West Haven, CT, USA
| | - Oliver D Howes
- Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- MRC London Institute of Medical Sciences, Imperial College London, Hammersmith Hospital, London, UK
- South London and Maudsley Foundation NHS Trust, Maudsley Hospital, London, UK
| |
Collapse
|
100
|
Elkahlah NA, Rogow JA, Ahmed M, Clowney EJ. Presynaptic developmental plasticity allows robust sparse wiring of the Drosophila mushroom body. eLife 2020; 9:e52278. [PMID: 31913123 PMCID: PMC7028369 DOI: 10.7554/elife.52278] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Accepted: 01/07/2020] [Indexed: 01/29/2023] Open
Abstract
In order to represent complex stimuli, principle neurons of associative learning regions receive combinatorial sensory inputs. Density of combinatorial innervation is theorized to determine the number of distinct stimuli that can be represented and distinguished from one another, with sparse innervation thought to optimize the complexity of representations in networks of limited size. How the convergence of combinatorial inputs to principle neurons of associative brain regions is established during development is unknown. Here, we explore the developmental patterning of sparse olfactory inputs to Kenyon cells of the Drosophila melanogaster mushroom body. By manipulating the ratio between pre- and post-synaptic cells, we find that postsynaptic Kenyon cells set convergence ratio: Kenyon cells produce fixed distributions of dendritic claws while presynaptic processes are plastic. Moreover, we show that sparse odor responses are preserved in mushroom bodies with reduced cellular repertoires, suggesting that developmental specification of convergence ratio allows functional robustness.
Collapse
Affiliation(s)
- Najia A Elkahlah
- Department of Molecular, Cellular and Developmental BiologyThe University of MichiganAnn ArborUnited States
| | - Jackson A Rogow
- Laboratory of Neurophysiology and BehaviorThe Rockefeller UniversityNew YorkUnited States
| | - Maria Ahmed
- Department of Molecular, Cellular and Developmental BiologyThe University of MichiganAnn ArborUnited States
| | - E Josephine Clowney
- Department of Molecular, Cellular and Developmental BiologyThe University of MichiganAnn ArborUnited States
| |
Collapse
|