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Joshi S, Haney S, Wang Z, Locatelli F, Lei H, Cao Y, Smith B, Bazhenov M. Plasticity in inhibitory networks improves pattern separation in early olfactory processing. Commun Biol 2025; 8:590. [PMID: 40204909 PMCID: PMC11982548 DOI: 10.1038/s42003-025-07879-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2024] [Accepted: 03/03/2025] [Indexed: 04/11/2025] Open
Abstract
Distinguishing between nectar and non-nectar odors is challenging for animals due to shared compounds and varying ratios in complex mixtures. Changes in nectar production throughout the day and over the animal's lifetime add to the complexity. The honeybee olfactory system, containing fewer than 1000 principal neurons in the early olfactory relay, the antennal lobe (AL), must learn to associate diverse volatile blends with rewards. Previous studies identified plasticity in the AL circuits, but its role in odor learning remains poorly understood. Using a biophysical computational model, tuned by in vivo electrophysiological data, and live imaging of the honeybee's AL, we explored the neural mechanisms of plasticity in the AL. Our findings revealed that when trained with a set of rewarded and unrewarded odors, the AL inhibitory network suppresses responses to shared chemical compounds while enhancing responses to distinct compounds. This results in improved pattern separation and a more concise neural code. Our calcium imaging data support these predictions. Analysis of a graph convolutional neural network performing an odor categorization task revealed a similar mechanism for contrast enhancement. Our study provides insights into how inhibitory plasticity in the early olfactory network reshapes the coding for efficient learning of complex odors.
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Affiliation(s)
- Shruti Joshi
- Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, CA, USA.
- Department of Medicine, University of California San Diego, La Jolla, CA, USA.
| | - Seth Haney
- Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Zhenyu Wang
- Department of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, AZ, USA
| | - Fernando Locatelli
- Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Instituto de Fisiología, Biología Molecular y Neurociencias, CONICET, Buenos Aires, Argentina
| | - Hong Lei
- School of Life Science, Arizona State University, Tempe, AZ, USA
| | - Yu Cao
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Brian Smith
- School of Life Science, Arizona State University, Tempe, AZ, USA
| | - Maxim Bazhenov
- Department of Medicine, University of California San Diego, La Jolla, CA, USA.
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2
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Manoim-Wolkovitz JE, Camchy T, Rozenfeld E, Chang HH, Lerner H, Chou YH, Darshan R, Parnas M. Nonlinear high-activity neuronal excitation enhances odor discrimination. Curr Biol 2025; 35:1521-1538.e5. [PMID: 40107267 PMCID: PMC11974548 DOI: 10.1016/j.cub.2025.02.034] [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: 06/04/2024] [Revised: 01/31/2025] [Accepted: 02/18/2025] [Indexed: 03/22/2025]
Abstract
Discrimination between different signals is crucial for animals' survival. Inhibition that suppresses weak neural activity is crucial for pattern decorrelation. Our understanding of alternative mechanics that allow efficient signal classification remains incomplete. We show that Drosophila olfactory receptor neurons (ORNs) have numerous intraglomerular axo-axonal connections mediated by the G protein-coupled receptor (GPCR), muscarinic type B receptor (mAChR-B). Contrary to its usual inhibitory role, mAChR-B participates in ORN excitation. The excitatory effect of mAChR-B only occurs at high ORN firing rates. A computational model demonstrates that nonlinear intraglomerular or global excitation decorrelates the activity patterns of ORNs of different types and improves odor classification and discrimination, while acting in concert with the previously known inhibition. Indeed, knocking down mAChR-B led to increased correlation in odor-induced ORN activity, which was associated with impaired odor discrimination, as shown in behavioral experiments. Furthermore, knockdown (KD) of mAChR-B and the GABAergic GPCR, GABAB-R, has an additive behavioral effect, causing reduced odor discrimination relative to single-KD flies. Together, this study unravels a novel mechanism for neuronal pattern decorrelation, which is based on nonlinear intraglomerular excitation.
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Affiliation(s)
- Julia E Manoim-Wolkovitz
- Department of Physiology and Pharmacology, Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Tal Camchy
- Department of Physiology and Pharmacology, Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv 69978, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | - Eyal Rozenfeld
- Department of Physiology and Pharmacology, Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv 69978, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | - Hao-Hsin Chang
- Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Science, National Defense Medical Center, Taipei 114201, Taiwan; Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Hadas Lerner
- Department of Physiology and Pharmacology, Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ya-Hui Chou
- Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Science, National Defense Medical Center, Taipei 114201, Taiwan; Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan; Neuroscience Program of Academia Sinica, Academia Sinica, Taipei 11529, Taiwan; Genome and Systems Biology Degree Program, Academia Sinica and National Taiwan University, Taipei 10617, Taiwan
| | - Ran Darshan
- Department of Physiology and Pharmacology, Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv 69978, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel; School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
| | - Moshe Parnas
- Department of Physiology and Pharmacology, Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv 69978, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel.
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3
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Joshi S, Haney S, Wang Z, Locatelli F, Lei H, Cao Y, Smith B, Bazhenov M. Plasticity in inhibitory networks improves pattern separation in early olfactory processing. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2025:2024.01.24.576675. [PMID: 38328149 PMCID: PMC10849730 DOI: 10.1101/2024.01.24.576675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Distinguishing between nectar and non-nectar odors is challenging for animals due to shared compounds and varying ratios in complex mixtures. Changes in nectar production throughout the day - and potentially many times within a forager's lifetime - add to the complexity. The honeybee olfactory system, containing fewer than 1,000 principal neurons in the early olfactory relay, the antennal lobe (AL), must learn to associate diverse volatile blends with rewards. Previous studies identified plasticity in the AL circuits, but its role in odor learning remains poorly understood. Using a biophysical computational network model, tuned by in vivo electrophysiological data, and live imaging of the honeybee's AL, we explored the neural mechanisms and functions of plasticity in the early olfactory system. Our findings revealed that when trained with a set of rewarded and unrewarded odors, the AL inhibitory network suppresses shared chemical compounds while enhancing responses to distinct compounds. This results in improved pattern separation and a more concise neural code. Our calcium imaging data support these predictions. Analysis of a graph convolutional neural network performing an odor categorization task revealed a similar mechanism for contrast enhancement. Our study provides insights into how inhibitory plasticity in the early olfactory network reshapes the coding for efficient learning of complex odors.
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Affiliation(s)
- Shruti Joshi
- Department of Electrical and Computer Engineering, University of California San Diego, USA
- Department of Medicine, University of California San Diego, USA
| | - Seth Haney
- Department of Medicine, University of California San Diego, USA
| | - Zhenyu Wang
- Department of Electrical, Computer and Energy Engineering, Arizona State University, USA
| | - Fernando Locatelli
- Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Instituto de Fisiología, Biología Molecular y Neurociencias, CONICET, Buenos Aires, Argentina
| | - Hong Lei
- School of Life Science, Arizona State University, USA
| | - Yu Cao
- Department of Electrical and Computer Engineering, University of Minnesota, USA
| | - Brian Smith
- School of Life Science, Arizona State University, USA
| | - Maxim Bazhenov
- Department of Medicine, University of California San Diego, USA
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4
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Leier HC, Foden AJ, Jindal DA, Wilkov AJ, Van der Linden Costello P, Vanderzalm PJ, Coutinho-Budd J, Tabuchi M, Broihier HT. Glia control experience-dependent plasticity in an olfactory critical period. eLife 2025; 13:RP100989. [PMID: 39883485 PMCID: PMC11781797 DOI: 10.7554/elife.100989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2025] Open
Abstract
Sensory experience during developmental critical periods has lifelong consequences for circuit function and behavior, but the molecular and cellular mechanisms through which experience causes these changes are not well understood. The Drosophila antennal lobe houses synapses between olfactory sensory neurons (OSNs) and downstream projection neurons (PNs) in stereotyped glomeruli. Many glomeruli exhibit structural plasticity in response to early-life odor exposure, indicating a general sensitivity of the fly olfactory circuitry to early sensory experience. We recently found that glia shape antennal lobe development in young adults, leading us to ask if glia also drive experience-dependent plasticity during this period. Here, we define a critical period for structural and functional plasticity of OSN-PN synapses in the ethyl butyrate (EB)-sensitive glomerulus VM7. EB exposure for the first 2 days post-eclosion drives large-scale reductions in glomerular volume, presynapse number, and post- synaptic activity. Crucially, pruning during the critical period has long-term consequences for circuit function since both OSN-PN synapse number and spontaneous activity of PNs remain persistently decreased following early-life odor exposure. The highly conserved engulfment receptor Draper is required for this critical period plasticity as ensheathing glia upregulate Draper, invade the VM7 glomerulus, and phagocytose OSN presynaptic terminals in response to critical-period EB exposure. Loss of Draper fully suppresses the morphological and physiological consequences of critical period odor exposure, arguing that phagocytic glia engulf intact synaptic terminals. These data demonstrate experience-dependent pruning of synapses and argue that Drosophila olfactory circuitry is a powerful model for defining the function of glia in critical period plasticity.
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Affiliation(s)
- Hans C Leier
- Department of Neurosciences, Case Western Reserve University School of MedicineClevelandUnited States
| | - Alexander J Foden
- Department of Neurosciences, Case Western Reserve University School of MedicineClevelandUnited States
| | - Darren A Jindal
- Department of Neurosciences, Case Western Reserve University School of MedicineClevelandUnited States
| | - Abigail J Wilkov
- Department of Neurosciences, Case Western Reserve University School of MedicineClevelandUnited States
| | | | - Pamela J Vanderzalm
- Department of Biology, John Carroll UniversityUniversity HeightsUnited States
| | - Jaeda Coutinho-Budd
- Department of Neuroscience, University of Virginia School of MedicineCharlottesvilleUnited States
| | - Masashi Tabuchi
- Department of Neurosciences, Case Western Reserve University School of MedicineClevelandUnited States
| | - Heather T Broihier
- Department of Neurosciences, Case Western Reserve University School of MedicineClevelandUnited States
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5
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Leier HC, Foden AJ, Jindal DA, Wilkov AJ, Costello PVDL, Vanderzalm PJ, Coutinho-Budd JC, Tabuchi M, Broihier HT. Glia control experience-dependent plasticity in an olfactory critical period. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.05.602232. [PMID: 39005309 PMCID: PMC11245089 DOI: 10.1101/2024.07.05.602232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Sensory experience during developmental critical periods has lifelong consequences for circuit function and behavior, but the molecular and cellular mechanisms through which experience causes these changes are not well understood. The Drosophila antennal lobe houses synapses between olfactory sensory neurons (OSNs) and downstream projection neurons (PNs) in stereotyped glomeruli. Many glomeruli exhibit structural plasticity in response to early-life odor exposure, indicating a general sensitivity of the fly olfactory circuitry to early sensory experience. We recently found that glia shape antennal lobe development in young adults, leading us to ask if glia also drive experience-dependent plasticity during this period. Here we define a critical period for structural and functional plasticity of OSN-PN synapses in the ethyl butyrate (EB)-sensitive glomerulus VM7. EB exposure for the first two days post-eclosion drives large-scale reductions in glomerular volume, presynapse number, and post-synaptic activity. Crucially, pruning during the critical period has long-term consequences for circuit function since both OSN-PN synapse number and spontaneous activity of PNs remain persistently decreased following early-life odor exposure. The highly conserved engulfment receptor Draper is required for this critical period plasticity as ensheathing glia upregulate Draper, invade the VM7 glomerulus, and phagocytose OSN presynaptic terminals in response to critical-period EB exposure. Loss of Draper fully suppresses the morphological and physiological consequences of critical period odor exposure, arguing that phagocytic glia engulf intact synaptic terminals. These data demonstrate experience-dependent pruning of synapses and argue that Drosophila olfactory circuitry is a powerful model for defining the function of glia in critical period plasticity.
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Affiliation(s)
- Hans C Leier
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, United States
| | - Alexander J Foden
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, United States
| | - Darren A Jindal
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, United States
| | - Abigail J Wilkov
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, United States
| | | | - Pamela J Vanderzalm
- Department of Biology, John Carroll University, University Heights, United States
| | - Jaeda C Coutinho-Budd
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, United States
| | - Masashi Tabuchi
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, United States
| | - Heather T Broihier
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, United States
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6
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Vaikakkara Chithran A, Allan DW, O'Connor TP. Adult expression of the cell adhesion protein Fasciclin 3 is required for the maintenance of adult olfactory interneurons. J Cell Sci 2024; 137:jcs261759. [PMID: 38934299 DOI: 10.1242/jcs.261759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 05/20/2024] [Indexed: 06/28/2024] Open
Abstract
The proper functioning of the nervous system is dependent on the establishment and maintenance of intricate networks of neurons that form functional neural circuits. Once neural circuits are assembled during development, a distinct set of molecular programs is likely required to maintain their connectivity throughout the lifetime of the organism. Here, we demonstrate that Fasciclin 3 (Fas3), an axon guidance cell adhesion protein, is necessary for the maintenance of the olfactory circuit in adult Drosophila. We utilized the TARGET system to spatiotemporally knockdown Fas3 in selected populations of adult neurons. Our findings show that Fas3 knockdown results in the death of olfactory circuit neurons and reduced survival of adults. We also demonstrated that Fas3 knockdown activates caspase-3-mediated cell death in olfactory local interneurons, which can be rescued by overexpressing baculovirus p35, an anti-apoptotic protein. This work adds to the growing set of evidence indicating a crucial role for axon guidance proteins in the maintenance of neuronal circuits in adults.
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Affiliation(s)
- Aarya Vaikakkara Chithran
- Graduate Program in Neuroscience, 3402-2215 Wesbrook Mall, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
- Department of Cellular and Physiological Sciences, 2350 Health Sciences Mall, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Douglas W Allan
- Department of Cellular and Physiological Sciences, 2350 Health Sciences Mall, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
- Djavad Mowafaghian Centre for Brain Health, 2215 Wesbrook Mall, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Timothy P O'Connor
- Department of Cellular and Physiological Sciences, 2350 Health Sciences Mall, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
- Djavad Mowafaghian Centre for Brain Health, 2215 Wesbrook Mall, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
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7
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Abubaker MB, Hsu FY, Feng KL, Chu LA, de Belle JS, Chiang AS. Asymmetric neurons are necessary for olfactory learning in the Drosophila brain. Curr Biol 2024; 34:946-957.e4. [PMID: 38320552 DOI: 10.1016/j.cub.2024.01.037] [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: 06/27/2023] [Revised: 10/31/2023] [Accepted: 01/15/2024] [Indexed: 02/08/2024]
Abstract
Animals have complementary parallel memory systems that process signals from various sensory modalities. In the brain of the fruit fly Drosophila melanogaster, mushroom body (MB) circuitry is the primary associative neuropil, critical for all stages of olfactory memory. Here, our findings suggest that active signaling from specific asymmetric body (AB) neurons is also crucial for this process. These AB neurons respond to odors and electric shock separately and exhibit timing-sensitive neuronal activity in response to paired stimulation while leaving a decreased memory trace during retrieval. Our experiments also show that rutabaga-encoded adenylate cyclase, which mediates coincidence detection, is required for learning and short-term memory in both AB and MB. We observed additive effects when manipulating rutabaga co-expression in both structures. Together, these results implicate the AB in playing a critical role in associative olfactory learning and short-term memory.
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Affiliation(s)
| | - Fu-Yu Hsu
- Institute of Biotechnology, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Kuan-Lin Feng
- Brain Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Li-An Chu
- Brain Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan; Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - J Steven de Belle
- Brain Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan; School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA; Department of Psychological Sciences, University of San Diego, San Diego, CA 92110, USA; School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, NV 89154, USA; MnemOdyssey LLC, Escondido, CA 92027, USA
| | - Ann-Shyn Chiang
- Brain Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan; Institute of Biotechnology, National Tsing Hua University, Hsinchu 30013, Taiwan; Institute of Systems Neuroscience, National Tsing Hua University, Hsinchu 30013, Taiwan; Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung 80708, Taiwan; Institute of Molecular and Genomic Medicine, National Health Research Institutes, Zhunan 35053, Taiwan; Graduate Institute of Clinical Medical Science, China Medical University, Taichung 40402, Taiwan.
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8
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Pírez N, Klappenbach M, Locatelli FF. Experience-dependent tuning of the olfactory system. CURRENT OPINION IN INSECT SCIENCE 2023; 60:101117. [PMID: 37741614 DOI: 10.1016/j.cois.2023.101117] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 09/12/2023] [Accepted: 09/14/2023] [Indexed: 09/25/2023]
Abstract
Insects rely on their sense of smell to navigate complex environments and make decisions regarding food and reproduction. However, in natural settings, the odors that convey this information may come mixed with environmental odors that can obscure their perception. Therefore, recognizing the presence of informative odors involves generalization and discrimination processes, which can be facilitated when there is a high contrast between stimuli, or the internal representation of the odors of interest outcompetes that of concurrent ones. The first two layers of the olfactory system, which involve the detection of odorants by olfactory receptor neurons and their encoding by the first postsynaptic partners in the antennal lobe, are critical for achieving such optimal representation. In this review, we summarize evidence indicating that experience-dependent changes adjust these two levels of the olfactory system. These changes are discussed in the context of the advantages they provide for detection of informative odors.
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Affiliation(s)
- Nicolás Pírez
- Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Instituto de Fisiología, Biología Molecular y Neurociencias, CONICET, C1428EHA Buenos Aires, Argentina
| | - Martín Klappenbach
- Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Instituto de Fisiología, Biología Molecular y Neurociencias, CONICET, C1428EHA Buenos Aires, Argentina
| | - Fernando F Locatelli
- Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Instituto de Fisiología, Biología Molecular y Neurociencias, CONICET, C1428EHA Buenos Aires, Argentina.
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9
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Chapochnikov NM, Pehlevan C, Chklovskii DB. Normative and mechanistic model of an adaptive circuit for efficient encoding and feature extraction. Proc Natl Acad Sci U S A 2023; 120:e2117484120. [PMID: 37428907 PMCID: PMC10629579 DOI: 10.1073/pnas.2117484120] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Accepted: 05/08/2023] [Indexed: 07/12/2023] Open
Abstract
One major question in neuroscience is how to relate connectomes to neural activity, circuit function, and learning. We offer an answer in the peripheral olfactory circuit of the Drosophila larva, composed of olfactory receptor neurons (ORNs) connected through feedback loops with interconnected inhibitory local neurons (LNs). We combine structural and activity data and, using a holistic normative framework based on similarity-matching, we formulate biologically plausible mechanistic models of the circuit. In particular, we consider a linear circuit model, for which we derive an exact theoretical solution, and a nonnegative circuit model, which we examine through simulations. The latter largely predicts the ORN [Formula: see text] LN synaptic weights found in the connectome and demonstrates that they reflect correlations in ORN activity patterns. Furthermore, this model accounts for the relationship between ORN [Formula: see text] LN and LN-LN synaptic counts and the emergence of different LN types. Functionally, we propose that LNs encode soft cluster memberships of ORN activity, and partially whiten and normalize the stimulus representations in ORNs through inhibitory feedback. Such a synaptic organization could, in principle, autonomously arise through Hebbian plasticity and would allow the circuit to adapt to different environments in an unsupervised manner. We thus uncover a general and potent circuit motif that can learn and extract significant input features and render stimulus representations more efficient. Finally, our study provides a unified framework for relating structure, activity, function, and learning in neural circuits and supports the conjecture that similarity-matching shapes the transformation of neural representations.
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Affiliation(s)
- Nikolai M. Chapochnikov
- Center for Computation Neuroscience, Flatiron Institute, New York, NY10010
- Department of Neurology, New York University School of Medicine, New York, NY10016
| | - Cengiz Pehlevan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA02138
- Center for Brain Science, Harvard University, Cambridge, MA02138
- Kempner Institute for the Study of Natural and Artificial Intelligence, Harvard University, Cambridge, MA02138
| | - Dmitri B. Chklovskii
- Center for Computation Neuroscience, Flatiron Institute, New York, NY10010
- Neuroscience Institute, New York University School of Medicine, New York, NY10016
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10
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Deanhardt B, Duan Q, Du C, Soeder C, Morlote A, Garg D, Saha A, Jones CD, Volkan PC. Social experience and pheromone receptor activity reprogram gene expression in sensory neurons. G3 (BETHESDA, MD.) 2023; 13:jkad072. [PMID: 36972331 PMCID: PMC10234412 DOI: 10.1093/g3journal/jkad072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Accepted: 03/11/2023] [Indexed: 06/29/2024]
Abstract
Social experience and pheromone signaling in olfactory neurons affect neuronal responses and male courtship behaviors in Drosophila. We previously showed that social experience and pheromone signaling modulate chromatin around behavioral switch gene fruitless, which encodes a transcription factor necessary and sufficient for male sexual behaviors. Fruitless drives social experience-dependent modulation of courtship behaviors and physiological sensory neuron responses to pheromone; however, the molecular mechanisms underlying this modulation of neural responses remain less clear. To identify the molecular mechanisms driving social experience-dependent changes in neuronal responses, we performed RNA-seq from antennal samples of mutants in pheromone receptors and fruitless, as well as grouped or isolated wild-type males. Genes affecting neuronal physiology and function, such as neurotransmitter receptors, ion channels, ion and membrane transporters, and odorant binding proteins are differentially regulated by social context and pheromone signaling. While we found that loss of pheromone detection only has small effects on differential promoter and exon usage within fruitless gene, many of the differentially regulated genes have Fruitless-binding sites or are bound by Fruitless in the nervous system. Recent studies showed that social experience and juvenile hormone signaling co-regulate fruitless chromatin to modify pheromone responses in olfactory neurons. Interestingly, genes involved in juvenile hormone metabolism are also misregulated in different social contexts and mutant backgrounds. Our results suggest that modulation of neuronal activity and behaviors in response to social experience and pheromone signaling likely arise due to large-scale changes in transcriptional programs for neuronal function downstream of behavioral switch gene function.
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Affiliation(s)
- Bryson Deanhardt
- Department of Biology, Duke University, Durham, NC 27708, USA
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Qichen Duan
- Department of Biology, Duke University, Durham, NC 27708, USA
| | - Chengcheng Du
- Department of Biology, Duke University, Durham, NC 27708, USA
| | - Charles Soeder
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Alec Morlote
- Department of Biology, Duke University, Durham, NC 27708, USA
| | - Deeya Garg
- Department of Biology, Duke University, Durham, NC 27708, USA
| | - Aishani Saha
- Department of Biology, Duke University, Durham, NC 27708, USA
| | - Corbin D Jones
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Pelin Cayirlioglu Volkan
- Department of Biology, Duke University, Durham, NC 27708, USA
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
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11
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Gugel ZV, Maurais EG, Hong EJ. Chronic exposure to odors at naturally occurring concentrations triggers limited plasticity in early stages of Drosophila olfactory processing. eLife 2023; 12:e85443. [PMID: 37195027 PMCID: PMC10229125 DOI: 10.7554/elife.85443] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 02/06/2023] [Indexed: 05/18/2023] Open
Abstract
In insects and mammals, olfactory experience in early life alters olfactory behavior and function in later life. In the vinegar fly Drosophila, flies chronically exposed to a high concentration of a monomolecular odor exhibit reduced behavioral aversion to the familiar odor when it is reencountered. This change in olfactory behavior has been attributed to selective decreases in the sensitivity of second-order olfactory projection neurons (PNs) in the antennal lobe that respond to the overrepresented odor. However, since odorant compounds do not occur at similarly high concentrations in natural sources, the role of odor experience-dependent plasticity in natural environments is unclear. Here, we investigated olfactory plasticity in the antennal lobe of flies chronically exposed to odors at concentrations that are typically encountered in natural odor sources. These stimuli were chosen to each strongly and selectively excite a single class of primary olfactory receptor neuron (ORN), thus facilitating a rigorous assessment of the selectivity of olfactory plasticity for PNs directly excited by overrepresented stimuli. Unexpectedly, we found that chronic exposure to three such odors did not result in decreased PN sensitivity but rather mildly increased responses to weak stimuli in most PN types. Odor-evoked PN activity in response to stronger stimuli was mostly unaffected by odor experience. When present, plasticity was observed broadly in multiple PN types and thus was not selective for PNs receiving direct input from the chronically active ORNs. We further investigated the DL5 olfactory coding channel and found that chronic odor-mediated excitation of its input ORNs did not affect PN intrinsic properties, local inhibitory innervation, ORN responses or ORN-PN synaptic strength; however, broad-acting lateral excitation evoked by some odors was increased. These results show that PN odor coding is only mildly affected by strong persistent activation of a single olfactory input, highlighting the stability of early stages of insect olfactory processing to significant perturbations in the sensory environment.
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Affiliation(s)
- Zhannetta V Gugel
- Division of Biology and Biological Engineering, California Institute of TechnologyPasadenaUnited States
| | - Elizabeth G Maurais
- Division of Biology and Biological Engineering, California Institute of TechnologyPasadenaUnited States
| | - Elizabeth J Hong
- Division of Biology and Biological Engineering, California Institute of TechnologyPasadenaUnited States
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12
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Zhao Y, Duan J, Han Z, Engström Y, Hartenstein V. Identification of a GABAergic neuroblast lineage modulating sweet and bitter taste sensitivity. Curr Biol 2022; 32:5354-5363.e3. [PMID: 36347251 PMCID: PMC10728805 DOI: 10.1016/j.cub.2022.10.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 06/16/2022] [Accepted: 10/14/2022] [Indexed: 11/09/2022]
Abstract
In Drosophila melanogaster, processing of gustatory information and controlling feeding behavior are executed by neural circuits located in the subesophageal zone (SEZ) of the brain.1 Gustatory receptor neurons (GRNs) project their axons in the primary gustatory center (PGC), which is located in the SEZ.1,2,3,4 To address the function of the PGC, we need detailed information about the different classes of gustatory interneurons that frame the PGC. In this work, we screened large collections of driver lines for SEZ interneuron-specific labeling and subsequently used candidate lines to access the SEZ neuroblast lineages. We converted 130 Gal4 lines to LexA drivers and carried out functional screening using calcium imaging. We found one neuroblast lineage, TRdm, whose neurons responded to both sweet and bitter tastants, and formed green fluorescent protein (GFP) reconstitution across synaptic partners (GRASP)-positive synapses with sweet sensory neurons. TRdm neurons express the inhibitory transmitter GABA, and silencing these neurons increases appetitive feeding behavior. These results demonstrate that TRdm generates a class of inhibitory local neurons that control taste sensitivity in Drosophila.
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Affiliation(s)
- Yunpo Zhao
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden; Biozentrum, University of Basel, 4056 Basel, Switzerland; Center for Precision Disease Modeling, University of Maryland School of Medicine, Baltimore 21201, USA.
| | - Jianli Duan
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden; Center for Precision Disease Modeling, University of Maryland School of Medicine, Baltimore 21201, USA
| | - Zhe Han
- Center for Precision Disease Modeling, University of Maryland School of Medicine, Baltimore 21201, USA
| | - Ylva Engström
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden
| | - Volker Hartenstein
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles 90095-1606, USA.
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13
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Blok LER, Boon M, van Reijmersdal B, Höffler KD, Fenckova M, Schenck A. Genetics, molecular control and clinical relevance of habituation learning. Neurosci Biobehav Rev 2022; 143:104883. [PMID: 36152842 DOI: 10.1016/j.neubiorev.2022.104883] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 08/08/2022] [Accepted: 08/30/2022] [Indexed: 11/29/2022]
Abstract
Habituation is the most fundamental form of learning. As a firewall that protects our brain from sensory overload, it is indispensable for cognitive processes. Studies in humans and animal models provide increasing evidence that habituation is affected in autism and related monogenic neurodevelopmental disorders (NDDs). An integrated application of habituation assessment in NDDs and their animal models has unexploited potential for neuroscience and medical care. With the aim to gain mechanistic insights, we systematically retrieved genes that have been demonstrated in the literature to underlie habituation. We identified 258 evolutionarily conserved genes across species, describe the biological processes they converge on, and highlight regulatory pathways and drugs that may alleviate habituation deficits. We also summarize current habituation paradigms and extract the most decisive arguments that support the crucial role of habituation for cognition in health and disease. We conclude that habituation is a conserved, quantitative, cognition- and disease-relevant process that can connect preclinical and clinical work, and hence is a powerful tool to advance research, diagnostics, and treatment of NDDs.
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Affiliation(s)
- Laura Elisabeth Rosalie Blok
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525GA, Nijmegen, the Netherlands.
| | - Marina Boon
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525GA, Nijmegen, the Netherlands.
| | - Boyd van Reijmersdal
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525GA, Nijmegen, the Netherlands.
| | - Kira Daniela Höffler
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525GA, Nijmegen, the Netherlands.
| | - Michaela Fenckova
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525GA, Nijmegen, the Netherlands; Department of Molecular Biology and Genetics, Faculty of Science, University of South Bohemia in Ceske Budejovice, Branisovska 31, 37005, Ceske Budejovice, Czech Republic.
| | - Annette Schenck
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525GA, Nijmegen, the Netherlands.
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14
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Lei H, Haney S, Jernigan CM, Guo X, Cook CN, Bazhenov M, Smith BH. Novelty detection in early olfactory processing of the honey bee, Apis mellifera. PLoS One 2022; 17:e0265009. [PMID: 35353837 PMCID: PMC8967009 DOI: 10.1371/journal.pone.0265009] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 02/20/2022] [Indexed: 11/19/2022] Open
Abstract
Animals are constantly bombarded with stimuli, which presents a fundamental problem of sorting among pervasive uninformative stimuli and novel, possibly meaningful stimuli. We evaluated novelty detection behaviorally in honey bees as they position their antennae differentially in an air stream carrying familiar or novel odors. We then characterized neuronal responses to familiar and novel odors in the first synaptic integration center in the brain-the antennal lobes. We found that the neurons that exhibited stronger initial responses to the odor that was to be familiarized are the same units that later distinguish familiar and novel odors, independently of chemical identities. These units, including both tentative projection neurons and local neurons, showed a decreased response to the familiar odor but an increased response to the novel odor. Our results suggest that the antennal lobe may represent familiarity or novelty to an odor stimulus in addition to its chemical identity code. Therefore, the mechanisms for novelty detection may be present in early sensory processing, either as a result of local synaptic interaction or via feedback from higher brain centers.
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Affiliation(s)
- Hong Lei
- School of Life Sciences, Arizona State University, Tempe, AZ, United States of America
| | - Seth Haney
- Department of Medicine, University of California, San Diego, CA, United States of America
| | | | - Xiaojiao Guo
- School of Life Sciences, Arizona State University, Tempe, AZ, United States of America
| | - Chelsea N. Cook
- School of Life Sciences, Arizona State University, Tempe, AZ, United States of America
| | - Maxim Bazhenov
- Department of Medicine, University of California, San Diego, CA, United States of America
| | - Brian H. Smith
- School of Life Sciences, Arizona State University, Tempe, AZ, United States of America
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15
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Ryan TJ, Frankland PW. Forgetting as a form of adaptive engram cell plasticity. Nat Rev Neurosci 2022; 23:173-186. [PMID: 35027710 DOI: 10.1038/s41583-021-00548-3] [Citation(s) in RCA: 64] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/25/2021] [Indexed: 12/30/2022]
Abstract
One leading hypothesis suggests that memories are stored in ensembles of neurons (or 'engram cells') and that successful recall involves reactivation of these ensembles. A logical extension of this idea is that forgetting occurs when engram cells cannot be reactivated. Forms of 'natural forgetting' vary considerably in terms of their underlying mechanisms, time course and reversibility. However, we suggest that all forms of forgetting involve circuit remodelling that switches engram cells from an accessible state (where they can be reactivated by natural recall cues) to an inaccessible state (where they cannot). In many cases, forgetting rates are modulated by environmental conditions and we therefore propose that forgetting is a form of neuroplasticity that alters engram cell accessibility in a manner that is sensitive to mismatches between expectations and the environment. Moreover, we hypothesize that disease states associated with forgetting may hijack natural forgetting mechanisms, resulting in reduced engram cell accessibility and memory loss.
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Affiliation(s)
- Tomás J Ryan
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland. .,Trinity College Institute for Neuroscience, Trinity College Dublin, Dublin, Ireland. .,Florey Institute of Neuroscience and Mental Health, Melbourne Brain Centre, University of Melbourne, Melbourne, Victoria, Australia. .,Child & Brain Development Program, Canadian Institute for Advanced Research (CIFAR), Toronto, Ontario, Canada.
| | - Paul W Frankland
- Child & Brain Development Program, Canadian Institute for Advanced Research (CIFAR), Toronto, Ontario, Canada. .,Program in Neurosciences & Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada. .,Department of Psychology, University of Toronto, Toronto, Ontario, Canada. .,Department of Physiology, University of Toronto, Toronto, Ontario, Canada. .,Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada.
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16
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Rozenfeld E, Tauber M, Ben-Chaim Y, Parnas M. GPCR voltage dependence controls neuronal plasticity and behavior. Nat Commun 2021; 12:7252. [PMID: 34903750 PMCID: PMC8668892 DOI: 10.1038/s41467-021-27593-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Accepted: 11/29/2021] [Indexed: 12/25/2022] Open
Abstract
G-protein coupled receptors (GPCRs) play a paramount role in diverse brain functions. Almost 20 years ago, GPCR activity was shown to be regulated by membrane potential in vitro, but whether the voltage dependence of GPCRs contributes to neuronal coding and behavioral output under physiological conditions in vivo has never been demonstrated. Here we show that muscarinic GPCR mediated neuronal potentiation in vivo is voltage dependent. This voltage dependent potentiation is abolished in mutant animals expressing a voltage independent receptor. Depolarization alone, without a muscarinic agonist, results in a nicotinic ionotropic receptor potentiation that is mediated by muscarinic receptor voltage dependency. Finally, muscarinic receptor voltage independence causes a strong behavioral effect of increased odor habituation. Together, this study identifies a physiological role for the voltage dependency of GPCRs by demonstrating crucial involvement of GPCR voltage dependence in neuronal plasticity and behavior. Thus, this study suggests that GPCR voltage dependency plays a role in many diverse neuronal functions including learning and memory.
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Affiliation(s)
- 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
| | - Merav Tauber
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, 43107, Israel
| | - Yair Ben-Chaim
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, 43107, Israel
| | - 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.
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17
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Abstract
The olfactory system translates chemical signals into neuronal signals that inform behavioral decisions of the animal. Odors are cues for source identity, but if monitored long enough, they can also be used to localize the source. Odor representations should therefore be robust to changing conditions and flexible in order to drive an appropriate behavior. In this review, we aim at discussing the main computations that allow robust and flexible encoding of odor information in the olfactory neural pathway.
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18
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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: 2.0] [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.
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19
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Glomerulus-Selective Regulation of a Critical Period for Interneuron Plasticity in the Drosophila Antennal Lobe. J Neurosci 2020; 40:5549-5560. [PMID: 32532889 PMCID: PMC7363474 DOI: 10.1523/jneurosci.2192-19.2020] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 05/30/2020] [Accepted: 06/02/2020] [Indexed: 11/21/2022] Open
Abstract
Several features of the adult nervous systems develop in a "critical period" (CP), during which high levels of plasticity allow neural circuits to be tuned for optimal performance. Through an analysis of long-term olfactory habituation (LTH) in female Drosophila, we provide new insight into mechanisms by which CPs are regulated in vivo LTH manifests as a persistently reduced behavioral response to an odorant encountered for 4 continuous days and occurs together with the growth of specific, odorant-responsive glomeruli in the antennal lobe. We show that the CP for behavioral and structural plasticity induced by ethyl butyrate (EB) or carbon dioxide (CO2) closes within 48 h after eclosion. The elaboration of excitatory projection neuron (PN) processes likely contribute to glomerular volume increases, as follows: both occur together and similarly require cAMP signaling in the antennal lobe inhibitory local interneurons. Further, the CP for structural plasticity could be extended beyond 48 h if EB- or CO2-responsive olfactory sensory neurons (OSNs) are silenced after eclosion; thus, OSN activity is required for closing the CP. Strikingly, silencing of glomerulus-selective OSNs extends the CP for structural plasticity only in respective target glomeruli. This indicates the existence of a local, short-range mechanism for regulating CP closure. Such a local mechanism for CP regulation can explain why plasticity induced by the odorant geranyl acetate (which is attractive) shows no CP although it involves the same core plasticity mechanisms as CO2 and EB. Local control of closure mechanisms during the critical period can potentially impart evolutionarily adaptive, odorant-specific features to behavioral plasticity.SIGNIFICANCE STATEMENT The critical period for plasticity represents a stage of life at which animals learn specific tasks or features with particular facility. This work provides fresh evidence that mechanisms for regulating critical periods are broadly conserved across evolution. Thus, a critical period for long-term olfactory habituation in Drosophila, which closes early in adulthood can, like the critical period for ocular dominance plasticity in mammals, be extended by blocking sensory neurons early in life. Further observations show that critical periods for plasticity can be regulated by spatially restricted mechanisms, potentially allowing varied critical periods for plasticity to stimuli of different ethological relevance.
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20
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Serotonin transporter dependent modulation of food-seeking behavior. PLoS One 2020; 15:e0227554. [PMID: 31978073 PMCID: PMC6980608 DOI: 10.1371/journal.pone.0227554] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 12/20/2019] [Indexed: 11/28/2022] Open
Abstract
The olfactory pathway integrates the odor information required to generate correct behavioral responses. To address how changes of serotonin signaling in two contralaterally projecting, serotonin-immunoreactive deutocerebral neurons impacts key odorant attraction in Drosophila melanogaster, we selectively alter serotonin signaling using the serotonin transporter with mutated serotonin binding sites in these neurons and analyzed the consequence on odorant-guided food seeking. The expression of the mutated serotonin transporter selectively changed the odorant attraction in an odorant-specific manner. The shift in attraction was not influenced by more up-stream serotonergic mechanisms mediating behavioral inhibition. The expression of the mutated serotonin transporter in CSD neurons did not influence other behaviors associated with food seeking such as olfactory learning and memory or food consumption. We provide evidence that the change in the attraction by serotonin transporter function might be achieved by increased serotonin signaling and by different serotonin receptors. The 5-HT1B receptor positively regulated the attraction to low and negatively regulated the attraction to high concentrations of acetic acid. In contrast, 5-HT1A and 5-HT2A receptors negatively regulated the attraction in projection neurons to high acetic acid concentrations. These results provide insights into how serotonin signaling in two serotonergic neurons selectively regulates the behavioral response to key odorants during food seeking.
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21
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Kita T, Mino H, Ozoe F, Ozoe Y. Spatiotemporally different expression of alternatively spliced GABA receptor subunit transcripts in the housefly Musca domestica. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2019; 101:e21541. [PMID: 30821008 DOI: 10.1002/arch.21541] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 02/01/2019] [Accepted: 02/07/2019] [Indexed: 06/09/2023]
Abstract
Insect γ-aminobutyric acid (GABA) receptors are important as major inhibitory neurotransmitter receptors and targets for insecticides. The housefly GABA receptor subunit gene MdRdl is alternatively spliced at exons 3 (a or b) and 6 (c or d) to yield the variants of ac, ad, bc, and bd combinations. In the present study, the expression of the MdRdl transcript in the body parts and in the developmental stages of the housefly Musca domestica was examined by quantitative polymerase chain reaction using specific primers that amplify the combinations of alternative exons. The results indicated that the transcripts of MdRdl, including four combinations, were highly expressed in the adult stage. MdRdlbd was the most abundant in the adult head. The expression pattern did not change in the adult stage over 7 days after eclosion. The expression level of the MdRdl bd transcript in the female head was similar to that of the male head. In contrast, MdRdl bc was the predominant transcript in the pupal head and the adult leg. Because the homomeric Rdl bc GABA receptor has a high affinity for GABA, our results provide grounds for designing agonist or competitive-antagonist insecticides that target the orthosteric site of the GABA receptor containing this Rdl variant.
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Affiliation(s)
- Tomo Kita
- Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Matsue, Shimane, Japan
| | - Hayata Mino
- Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Matsue, Shimane, Japan
| | - Fumiyo Ozoe
- Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Matsue, Shimane, Japan
| | - Yoshihisa Ozoe
- Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Matsue, Shimane, Japan
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22
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Cook CN, Mosquiero T, Brent CS, Ozturk C, Gadau J, Pinter-Wollman N, Smith BH. Individual differences in learning and biogenic amine levels influence the behavioural division between foraging honeybee scouts and recruits. J Anim Ecol 2019; 88:236-246. [PMID: 30289166 PMCID: PMC6379132 DOI: 10.1111/1365-2656.12911] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 08/31/2018] [Indexed: 11/29/2022]
Abstract
Animals must effectively balance the time they spend exploring the environment for new resources and exploiting them. One way that social animals accomplish this balance is by allocating these two tasks to different individuals. In honeybees, foraging is divided between scouts, which tend to explore the landscape for novel resources, and recruits, which tend to exploit these resources. Exploring the variation in cognitive and physiological mechanisms of foraging behaviour will provide a deeper understanding of how the division of labour is regulated in social insect societies. Here, we uncover how honeybee foraging behaviour may be shaped by predispositions in performance of latent inhibition (LI), which is a form of non-associative learning by which individuals learn to ignore familiar information. We compared LI between scouts and recruits, hypothesizing that differences in learning would correlate with differences in foraging behaviour. Scouts seek out and encounter many new odours while locating novel resources, while recruits continuously forage from the same resource, even as its quality degrades. We found that scouts show stronger LI than recruits, possibly reflecting their need to discriminate forage quality. We also found that scouts have significantly elevated tyramine compared to recruits. Furthermore, after associative odour training, recruits have significantly diminished octopamine in their brains compared to scouts. These results suggest that individual variation in learning behaviour shapes the phenotypic behavioural differences between different types of honeybee foragers. These differences in turn have important consequences for how honeybee colonies interact with their environment. Uncovering the proximate mechanisms that influence individual variation in foraging behaviour is crucial for understanding the ecological context in which societies evolve.
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Affiliation(s)
- Chelsea N Cook
- Arizona State University, School of Life Sciences, Tempe, Arizona
| | - Thiago Mosquiero
- University of California at Los Angeles, Department of Evolutionary Biology, Los Angeles, California
| | - Colin S. Brent
- USDA – ALARC, Department of Pest Management, Maricopa, Arizona
| | - Cahit Ozturk
- Arizona State University, School of Life Sciences, Tempe, Arizona
| | - Jürgen Gadau
- Institute for Evolution and Biodiversity, University of Münster Germany
| | - Noa Pinter-Wollman
- University of California at Los Angeles, Department of Evolutionary Biology, Los Angeles, California
| | - Brian H. Smith
- Arizona State University, School of Life Sciences, Tempe, Arizona
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23
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Semelidou O, Acevedo SF, Skoulakis EM. Temporally specific engagement of distinct neuronal circuits regulating olfactory habituation in Drosophila. eLife 2018; 7:39569. [PMID: 30576281 PMCID: PMC6303106 DOI: 10.7554/elife.39569] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 11/29/2018] [Indexed: 11/13/2022] Open
Abstract
Habituation is the process that enables salience filtering, precipitating perceptual changes that alter the value of environmental stimuli. To discern the neuronal circuits underlying habituation to brief inconsequential stimuli, we developed a novel olfactory habituation paradigm, identifying two distinct phases of the response that engage distinct neuronal circuits. Responsiveness to the continuous odor stimulus is maintained initially, a phase we term habituation latency and requires Rutabaga Adenylyl-Cyclase-depended neurotransmission from GABAergic Antennal Lobe Interneurons and activation of excitatory Projection Neurons (PNs) and the Mushroom Bodies. In contrast, habituation depends on the inhibitory PNs of the middle Antenno-Cerebral Track, requires inner Antenno-Cerebral Track PN activation and defines a temporally distinct phase. Collectively, our data support the involvement of Lateral Horn excitatory and inhibitory stimulation in habituation. These results provide essential cellular substrates for future analyses of the molecular mechanisms that govern the duration and transition between these distinct temporal habituation phases. Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
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Affiliation(s)
- Ourania Semelidou
- Division of Neuroscience, Biomedical Sciences Research Centre "Alexander Fleming", Vari, Greece.,School of Medicine, University of Crete, Heraklion, Greece
| | - Summer F Acevedo
- Division of Neuroscience, Biomedical Sciences Research Centre "Alexander Fleming", Vari, Greece
| | - Efthimios Mc Skoulakis
- Division of Neuroscience, Biomedical Sciences Research Centre "Alexander Fleming", Vari, Greece
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24
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Andrione M, Timberlake BF, Vallortigara G, Antolini R, Haase A. Morphofunctional experience-dependent plasticity in the honeybee brain. ACTA ACUST UNITED AC 2017; 24:622-629. [PMID: 29142057 PMCID: PMC5688957 DOI: 10.1101/lm.046243.117] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 08/11/2017] [Indexed: 11/25/2022]
Abstract
Repeated or prolonged exposure to an odorant without any positive or negative reinforcement produces experience-dependent plasticity, which results in habituation and latent inhibition. In the honeybee (Apis mellifera), it has been demonstrated that, even if the absolute neural representation of an odor in the primary olfactory center, the antennal lobe (AL), is not changed by repeated presentations, its relative representation with respect to unfamiliar stimuli is modified. In particular, the representation of a stimulus composed of a 50:50 mixture of a familiar and a novel odorant becomes more similar to that of the novel stimulus after repeated stimulus preexposure. In a calcium-imaging study, we found that the same functional effect develops following prolonged odor exposure. By analyzing the brains of the animals subjected to this procedure, we found that such functional changes are accompanied by morphological changes in the AL (i.e., a decrease in volume in specific glomeruli). The AL glomeruli that exhibited structural plasticity also modified their functional responses to the three stimuli (familiar odor, novel odor, binary mixture). We suggest a model in which rebalancing inhibition within the AL glomeruli may be sufficient to elicit structural and functional correlates of experience-dependent plasticity.
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Affiliation(s)
- Mara Andrione
- Center for Mind/Brain Sciences, University of Trento, 38068 Rovereto, Italy
| | | | | | - Renzo Antolini
- Center for Mind/Brain Sciences, University of Trento, 38068 Rovereto, Italy.,Department of Physics, University of Trento, 38120 Trento, Italy
| | - Albrecht Haase
- Center for Mind/Brain Sciences, University of Trento, 38068 Rovereto, Italy.,Department of Physics, University of Trento, 38120 Trento, Italy
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25
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Hennequin G, Agnes EJ, Vogels TP. Inhibitory Plasticity: Balance, Control, and Codependence. Annu Rev Neurosci 2017; 40:557-579. [DOI: 10.1146/annurev-neuro-072116-031005] [Citation(s) in RCA: 140] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Guillaume Hennequin
- Computational and Biological Learning Lab, Department of Engineering, University of Cambridge, Cambridge CB2 3EJ, United Kingdom
| | - Everton J. Agnes
- Centre for Neural Circuits and Behaviour, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3SR, United Kingdom
| | - Tim P. Vogels
- Centre for Neural Circuits and Behaviour, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3SR, United Kingdom
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26
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Abstract
Nervous systems use excitatory cell assemblies to encode and represent sensory percepts. Similarly, synaptically connected cell assemblies or "engrams" are thought to represent memories of past experience. Multiple lines of recent evidence indicate that brain systems create and use inhibitory replicas of excitatory representations for important cognitive functions. Such matched "inhibitory engrams" can form through homeostatic potentiation of inhibition onto postsynaptic cells that show increased levels of excitation. Inhibitory engrams can reduce behavioral responses to familiar stimuli, thereby resulting in behavioral habituation. In addition, by preventing inappropriate activation of excitatory memory engrams, inhibitory engrams can make memories quiescent, stored in a latent form that is available for context-relevant activation. In neural networks with balanced excitatory and inhibitory engrams, the release of innate responses and recall of associative memories can occur through focused disinhibition. Understanding mechanisms that regulate the formation and expression of inhibitory engrams in vivo may help not only to explain key features of cognition but also to provide insight into transdiagnostic traits associated with psychiatric conditions such as autism, schizophrenia, and posttraumatic stress disorder.
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27
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Kumar G, Ching S. The Geometry of Plasticity-Induced Sensitization in Isoinhibitory Rate Motifs. Neural Comput 2016; 28:1889-926. [PMID: 27391684 DOI: 10.1162/neco_a_00865] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
A well-known phenomenon in sensory perception is desensitization, wherein behavioral responses to persistent stimuli become attenuated over time. In this letter, our focus is on studying mechanisms through which desensitization may be mediated at the network level and, specifically, how sensitivity changes arise as a function of long-term plasticity. Our principal object of study is a generic isoinhibitory motif: a small excitatory-inhibitory network with recurrent inhibition. Such a motif is of interest due to its overrepresentation in laminar sensory network architectures. Here, we introduce a sensitivity analysis derived from control theory in which we characterize the fixed-energy reachable set of the motif. This set describes the regions of the phase-space that are more easily (in terms of stimulus energy) accessed, thus providing a holistic assessment of sensitivity. We specifically focus on how the geometry of this set changes due to repetitive application of a persistent stimulus. We find that for certain motif dynamics, this geometry contracts along the stimulus orientation while expanding in orthogonal directions. In other words, the motif not only desensitizes to the persistent input, but heightens its responsiveness (sensitizes) to those that are orthogonal. We develop a perturbation analysis that links this sensitization to both plasticity-induced changes in synaptic weights and the intrinsic dynamics of the network, highlighting that the effect is not purely due to weight-dependent disinhibition. Instead, this effect depends on the relative neuronal time constants and the consequent stimulus-induced drift that arises in the motif phase-space. For tightly distributed (but random) parameter ranges, sensitization is quite generic and manifests in larger recurrent E-I networks within which the motif is embedded.
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Affiliation(s)
- Gautam Kumar
- Electrical and Systems Engineering Washington University in St. Louis, St. Louis, MO 63130, U.S.A.
| | - ShiNung Ching
- Electrical and Systems Engineering Washington University in St. Louis, St. Louis, MO 63130, U.S.A.
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Rybak J, Talarico G, Ruiz S, Arnold C, Cantera R, Hansson BS. Synaptic circuitry of identified neurons in the antennal lobe of Drosophila melanogaster. J Comp Neurol 2016; 524:1920-56. [PMID: 26780543 PMCID: PMC6680330 DOI: 10.1002/cne.23966] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 01/05/2016] [Accepted: 01/13/2016] [Indexed: 11/09/2022]
Abstract
In Drosophila melanogaster olfactory sensory neurons (OSNs) establish synapses with projection neurons (PNs) and local interneurons within antennal lobe (AL) glomeruli. Substantial knowledge regarding this circuitry has been obtained by functional studies, whereas ultrastructural evidence of synaptic contacts is scarce. To fill this gap, we studied serial sections of three glomeruli using electron microscopy. Ectopic expression of a membrane-bound peroxidase allowed us to map synaptic sites along PN dendrites. Our data prove for the first time that each of the three major types of AL neurons is both pre- and postsynaptic to the other two types, as previously indicated by functional studies. PN dendrites carry a large proportion of output synapses, with approximately one output per every three input synapses. Detailed reconstructions of PN dendrites showed that these synapses are distributed unevenly, with input and output sites partially segregated along a proximal-distal gradient and the thinnest branches carrying solely input synapses. Moreover, our data indicate synapse clustering, as we found evidence of dendritic tiling of PN dendrites. PN output synapses exhibited T-shaped presynaptic densities, mostly arranged as tetrads. In contrast, output synapses from putative OSNs showed elongated presynaptic densities in which the T-bar platform was supported by several pedestals and contacted as many as 20 postsynaptic profiles. We also discovered synaptic contacts between the putative OSNs. The average synaptic density in the glomerular neuropil was about two synapses/µm(3) . These results are discussed with regard to current models of olfactory glomerular microcircuits across species.
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Affiliation(s)
- Jürgen Rybak
- Department of Evolutionary NeuroethologyMax Planck Institute for Chemical Ecology07745JenaGermany
| | - Giovanni Talarico
- Department of Evolutionary NeuroethologyMax Planck Institute for Chemical Ecology07745JenaGermany
| | - Santiago Ruiz
- Clemente Estable Institute of Biological Research11600 MontevideoUruguay
| | - Christopher Arnold
- Department of Evolutionary NeuroethologyMax Planck Institute for Chemical Ecology07745JenaGermany
| | - Rafael Cantera
- Clemente Estable Institute of Biological Research11600 MontevideoUruguay
- Zoology DepartmentStockholm University10691StockholmSweden
| | - Bill S. Hansson
- Department of Evolutionary NeuroethologyMax Planck Institute for Chemical Ecology07745JenaGermany
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GABAB receptor-mediated, layer-specific synaptic plasticity reorganizes gamma-frequency neocortical response to stimulation. Proc Natl Acad Sci U S A 2016; 113:E2721-9. [PMID: 27118845 DOI: 10.1073/pnas.1605243113] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Repeated presentations of sensory stimuli generate transient gamma-frequency (30-80 Hz) responses in neocortex that show plasticity in a task-dependent manner. Complex relationships between individual neuronal outputs and the mean, local field potential (population activity) accompany these changes, but little is known about the underlying mechanisms responsible. Here we show that transient stimulation of input layer 4 sufficient to generate gamma oscillations induced two different, lamina-specific plastic processes that correlated with lamina-specific changes in responses to further, repeated stimulation: Unit rates and recruitment showed overall enhancement in supragranular layers and suppression in infragranular layers associated with excitatory or inhibitory synaptic potentiation onto principal cells, respectively. Both synaptic processes were critically dependent on activation of GABAB receptors and, together, appeared to temporally segregate the cortical representation. These data suggest that adaptation to repetitive sensory input dramatically alters the spatiotemporal properties of the neocortical response in a manner that may both refine and minimize cortical output simultaneously.
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Tachibana SI, Touhara K, Ejima A. Modification of Male Courtship Motivation by Olfactory Habituation via the GABAA Receptor in Drosophila melanogaster. PLoS One 2015; 10:e0135186. [PMID: 26252206 PMCID: PMC4529276 DOI: 10.1371/journal.pone.0135186] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 07/18/2015] [Indexed: 11/29/2022] Open
Abstract
A male-specific component, 11-cis-vaccenyl acetate (cVA) works as an anti-aphrodisiac pheromone in Drosophila melanogaster. The presence of cVA on a male suppresses the courtship motivation of other males and contributes to suppression of male-male homosexual courtship, while the absence of cVA on a female stimulates the sexual motivation of nearby males and enhances the male-female interaction. However, little is known how a male distinguishes the presence or absence of cVA on a target fly from either self-produced cVA or secondhand cVA from other males in the vicinity. In this study, we demonstrate that male flies have keen sensitivity to cVA; therefore, the presence of another male in the area reduces courtship toward a female. This reduced level of sexual motivation, however, could be overcome by pretest odor exposure via olfactory habituation to cVA. Real-time imaging of cVA-responsive sensory neurons using the neural activity sensor revealed that prolonged exposure to cVA decreased the levels of cVA responses in the primary olfactory center. Pharmacological and genetic screening revealed that signal transduction via GABAA receptors contributed to this olfactory habituation. We also found that the habituation experience increased the copulation success of wild-type males in a group. In contrast, transgenic males, in which GABA input in a small subset of local neurons was blocked by RNAi, failed to acquire the sexual advantage conferred by habituation. Thus, we illustrate a novel phenomenon in which olfactory habituation positively affects sexual capability in a competitive environment.
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Affiliation(s)
- Shin-Ichiro Tachibana
- Career-Path Promotion Unit for Young Life Scientists, Kyoto University, Kyoto, 606–8501, Japan
- Department of Biology and Geosciences, Graduate School of Science, Osaka City University, Osaka, 558–8585, Japan
| | - Kazushige Touhara
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, 113–8657, Japan
- ERATO Touhara Chemosensory Signal Project, JST, The University of Tokyo, Tokyo, 113–8657, Japan
| | - Aki Ejima
- Career-Path Promotion Unit for Young Life Scientists, Kyoto University, Kyoto, 606–8501, Japan
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, 113–8657, Japan
- ERATO Touhara Chemosensory Signal Project, JST, The University of Tokyo, Tokyo, 113–8657, Japan
- * E-mail:
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Abstract
Chemotaxis is important for the survival of most animals. How the brain translates sensory input into motor output beyond higher olfactory processing centers is largely unknown. We describe a group of excitatory neurons, termed Odd neurons, which are important for Drosophila larval chemotaxis. Odd neurons receive synaptic input from projection neurons in the calyx of the mushroom body and project axons to the central brain. Functional imaging shows that some of the Odd neurons respond to odor. Larvae in which Odd neurons are silenced are less efficient at odor tracking than controls and sample the odor space more frequently. Larvae in which the excitability of Odd neurons is increased are better at odor intensity discrimination and odor tracking. Thus, the Odd neurons represent a distinct pathway that regulates the sensitivity of the olfactory system to odor concentrations, demonstrating that efficient chemotaxis depends on processing of odor strength downstream of higher olfactory centers.
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Abstract
Honey bees have a rich repertoire of olfactory learning behaviors, and they therefore are an excellent model to study plasticity in olfactory circuits. Recent behavioral, physiological, and molecular evidence suggested that the antennal lobe, the first relay of the olfactory system in insects and analog to the olfactory bulb in vertebrates, is involved in associative and nonassociative olfactory learning. Here we use calcium imaging to reveal how responses across antennal lobe projection neurons change after association of an input odor with appetitive reinforcement. After appetitive conditioning to 1-hexanol, the representation of an odor mixture containing 1-hexanol becomes more similar to this odor and less similar to the background odor acetophenone. We then apply computational modeling to investigate how changes in synaptic connectivity can account for the observed plasticity. Our study suggests that experience-dependent modulation of inhibitory interactions in the antennal lobe aids perception of salient odor components mixed with behaviorally irrelevant background odors.
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Abstract
The ability of organisms to seamlessly ignore familiar, inconsequential stimuli improves their selective attention and response to salient features of the environment. Here, I propose that this fundamental but unexplained phenomenon substantially derives from the ability of any pattern of neural excitation to create an enhanced inhibitory (or "negative") image of itself through target-specific scaling of inhibitory inputs onto active excitatory neurons. Familiar stimuli encounter strong negative images and are therefore less likely to be transmitted to higher brain centers. Integrating historical and recent observations, the negative-image model described here provides a mechanistic framework for understanding habituation, which is connected to ideas on dynamic predictive coding. In addition, it suggests insights for understanding autism spectrum disorders.
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Liu H, Zhou B, Yan W, Lei Z, Zhao X, Zhang K, Guo A. Astrocyte-like glial cells physiologically regulate olfactory processing through the modification of ORN-PN synaptic strength in Drosophila. Eur J Neurosci 2014; 40:2744-54. [PMID: 24964821 DOI: 10.1111/ejn.12646] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 04/26/2014] [Accepted: 05/02/2014] [Indexed: 11/29/2022]
Abstract
Astrocyte-like glial cells are abundant in the central nervous system of adult Drosophila and exhibit morphology similar to astrocytes of mammals. Previous evidence has shown that astrocyte-like glial cells are strongly associated with synapses in the antennal lobe (AL), the first relay of the olfactory system, where olfactory receptor neurons (ORNs) transmit information into projection neurons (PNs). However, the function of astrocyte-like glia in the AL remains obscure. In this study, using in vivo calcium imaging, we found that astrocyte-like glial cells exhibited spontaneous microdomain calcium elevations. Using simultaneous manipulation of glial activity and monitoring of neuronal function, we found that the astrocyte-like glial activation, but not ensheathing glial activation, could inhibit odor-evoked responses of PNs. Ensheathing glial cells are another subtype of glia, and are of functional importance in the AL. Electrophysiological experiments indicated that astrocyte-like glial activation decreased the amplitude and slope of excitatory postsynaptic potentials evoked through electrical stimulation of the antennal nerve. These results suggest that astrocyte-like glial cells may regulate olfactory processing through negative regulation of ORN-PN synaptic strength. Beyond the antennal lobe we observed astrocyte-like glial spontaneous calcium activities in the ventromedial protocerebrum, indicating that astrocyte-like glial spontaneous calcium elevations might be general in the adult fly brain. Overall, our study demonstrates a new function for astrocyte-like glial cells in the physiological modulation of olfactory information transmission, possibly through regulating ORN-PN synapse strength.
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Affiliation(s)
- He Liu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Shanghai, China
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Twick I, Lee JA, Ramaswami M. Olfactory habituation in Drosophila-odor encoding and its plasticity in the antennal lobe. PROGRESS IN BRAIN RESEARCH 2014; 208:3-38. [PMID: 24767477 DOI: 10.1016/b978-0-444-63350-7.00001-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
A ubiquitous feature of an animal's response to an odorant is that it declines when the odorant is frequently or continuously encountered. This decline in olfactory response, termed olfactory habituation, can have temporally or mechanistically different forms. The neural circuitry of the fruit fly Drosophila melanogaster's olfactory system is well defined in terms of component cells, which are readily accessible to functional studies and genetic manipulation. This makes it a particularly useful preparation for the investigation of olfactory habituation. In addition, the insect olfactory system shares many architectural and functional similarities with mammalian olfactory systems, suggesting that olfactory mechanisms in insects may be broadly relevant. In this chapter, we discuss the likely mechanisms of olfactory habituation in context of the participating cell types, their connectivity, and their roles in sensory processing. We overview the structure and function of key cell types, the mechanisms that stimulate them, and how they transduce and process odor signals. We then consider how each stage of olfactory processing could potentially contribute to behavioral habituation. After this, we overview a variety of recent mechanistic studies that point to an important role for potentiation of inhibitory synapses in the primary olfactory processing center, the antennal lobe, in driving the reduced response to familiar odorants. Following the discussion of mechanisms for short- and long-term olfactory habituation, we end by considering how these mechanisms may be regulated by neuromodulators, which likely play key roles in the induction, gating, or suppression of habituated behavior, and speculate on the relevance of these processes for other forms of learning and memory.
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Affiliation(s)
- Isabell Twick
- School of Genetics and Microbiology and School of Natural Sciences, Smurfit Institute of Genetics, Trinity College Institute of Neuroscience, Trinity College Dublin, Ireland.
| | - John Anthony Lee
- School of Genetics and Microbiology and School of Natural Sciences, Smurfit Institute of Genetics, Trinity College Institute of Neuroscience, Trinity College Dublin, Ireland.
| | - Mani Ramaswami
- School of Genetics and Microbiology and School of Natural Sciences, Smurfit Institute of Genetics, Trinity College Institute of Neuroscience, Trinity College Dublin, Ireland; National Centre for Biological Science, Bangalore, India
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FMRP and Ataxin-2 function together in long-term olfactory habituation and neuronal translational control. Proc Natl Acad Sci U S A 2013; 111:E99-E108. [PMID: 24344294 DOI: 10.1073/pnas.1309543111] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Fragile X mental retardation protein (FMRP) and Ataxin-2 (Atx2) are triplet expansion disease- and stress granule-associated proteins implicated in neuronal translational control and microRNA function. We show that Drosophila FMRP (dFMR1) is required for long-term olfactory habituation (LTH), a phenomenon dependent on Atx2-dependent potentiation of inhibitory transmission from local interneurons (LNs) to projection neurons (PNs) in the antennal lobe. dFMR1 is also required for LTH-associated depression of odor-evoked calcium transients in PNs. Strong transdominant genetic interactions among dFMR1, atx2, the deadbox helicase me31B, and argonaute1 (ago1) mutants, as well as coimmunoprecitation of dFMR1 with Atx2, indicate that dFMR1 and Atx2 function together in a microRNA-dependent process necessary for LTH. Consistently, PN or LN knockdown of dFMR1, Atx2, Me31B, or the miRNA-pathway protein GW182 increases expression of a Ca2+/calmodulin-dependent protein kinase II (CaMKII) translational reporter. Moreover, brain immunoprecipitates of dFMR1 and Atx2 proteins include CaMKII mRNA, indicating respective physical interactions with this mRNA. Because CaMKII is necessary for LTH, these data indicate that fragile X mental retardation protein and Atx2 act via at least one common target RNA for memory-associated long-term synaptic plasticity. The observed requirement in LNs and PNs supports an emerging view that both presynaptic and postsynaptic translation are necessary for long-term synaptic plasticity. However, whereas Atx2 is necessary for the integrity of dendritic and somatic Me31B-containing particles, dFmr1 is not. Together, these data indicate that dFmr1 and Atx2 function in long-term but not short-term memory, regulating translation of at least some common presynaptic and postsynaptic target mRNAs in the same cells.
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Synapsin function in GABA-ergic interneurons is required for short-term olfactory habituation. J Neurosci 2013; 33:16576-85. [PMID: 24133261 DOI: 10.1523/jneurosci.3142-13.2013] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In Drosophila, short-term (STH) and long-term habituation (LTH) of olfactory avoidance behavior are believed to arise from the selective potentiation of GABAergic synapses between multiglomerular local circuit interneurons (LNs) and projection neurons in the antennal lobe. However, the underlying mechanisms remain poorly understood. Here, we show that synapsin (syn) function is necessary for STH and that syn(97)-null mutant defects in STH can be rescued by syn(+) cDNA expression solely in the LN1 subset of GABAergic local interneurons. As synapsin is a synaptic vesicle-clustering phosphoprotein, these observations identify a presynaptic mechanism for STH as well as the inhibitory interneurons in which this mechanism is deployed. Serine residues 6 and/or 533, potential kinase target sites of synapsin, are necessary for synapsin function suggesting that synapsin phosphorylation is essential for STH. Consistently, biochemical analyses using a phospho-synapsin-specific antiserum show that synapsin is a target of Ca(2+) calmodulin-dependent kinase II (CaMKII) phosphorylation in vivo. Additional behavioral and genetic observations demonstrate that CaMKII function is necessary in LNs for STH. Together, these data support a model in which CaMKII-mediated synapsin phosphorylation in LNs induces synaptic vesicle mobilization and thereby presynaptic facilitation of GABA release that underlies olfactory STH. Finally, the striking observation that LTH occurs normally in syn(97) mutants indicates that signaling pathways for STH and LTH diverge upstream of synapsin function in GABAergic interneurons.
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Moreau AW, Kullmann DM. NMDA receptor-dependent function and plasticity in inhibitory circuits. Neuropharmacology 2013; 74:23-31. [DOI: 10.1016/j.neuropharm.2013.03.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 02/20/2013] [Accepted: 03/01/2013] [Indexed: 01/22/2023]
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Serrano E, Nowotny T, Levi R, Smith BH, Huerta R. Gain control network conditions in early sensory coding. PLoS Comput Biol 2013; 9:e1003133. [PMID: 23874176 PMCID: PMC3715526 DOI: 10.1371/journal.pcbi.1003133] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 05/26/2013] [Indexed: 11/19/2022] Open
Abstract
Gain control is essential for the proper function of any sensory system. However, the precise mechanisms for achieving effective gain control in the brain are unknown. Based on our understanding of the existence and strength of connections in the insect olfactory system, we analyze the conditions that lead to controlled gain in a randomly connected network of excitatory and inhibitory neurons. We consider two scenarios for the variation of input into the system. In the first case, the intensity of the sensory input controls the input currents to a fixed proportion of neurons of the excitatory and inhibitory populations. In the second case, increasing intensity of the sensory stimulus will both, recruit an increasing number of neurons that receive input and change the input current that they receive. Using a mean field approximation for the network activity we derive relationships between the parameters of the network that ensure that the overall level of activity of the excitatory population remains unchanged for increasing intensity of the external stimulation. We find that, first, the main parameters that regulate network gain are the probabilities of connections from the inhibitory population to the excitatory population and of the connections within the inhibitory population. Second, we show that strict gain control is not achievable in a random network in the second case, when the input recruits an increasing number of neurons. Finally, we confirm that the gain control conditions derived from the mean field approximation are valid in simulations of firing rate models and Hodgkin-Huxley conductance based models.
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Affiliation(s)
- Eduardo Serrano
- GNB, Escuela Politécnica Superior, Universidad Autónoma de Madrid, Madrid, Spain
| | - Thomas Nowotny
- CCNR, Informatics, University of Sussex, Brighton, United Kingdom
| | - Rafael Levi
- GNB, Escuela Politécnica Superior, Universidad Autónoma de Madrid, Madrid, Spain
- Department of Neurobiology and Behavior, University of California, Irvine, California, United States of America
| | - Brian H. Smith
- School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | - Ramón Huerta
- BioCircuits Institute, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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Glutamate is an inhibitory neurotransmitter in the Drosophila olfactory system. Proc Natl Acad Sci U S A 2013; 110:10294-9. [PMID: 23729809 DOI: 10.1073/pnas.1220560110] [Citation(s) in RCA: 208] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Glutamatergic neurons are abundant in the Drosophila central nervous system, but their physiological effects are largely unknown. In this study, we investigated the effects of glutamate in the Drosophila antennal lobe, the first relay in the olfactory system and a model circuit for understanding olfactory processing. In the antennal lobe, one-third of local neurons are glutamatergic. Using in vivo whole-cell patch clamp recordings, we found that many glutamatergic local neurons are broadly tuned to odors. Iontophoresed glutamate hyperpolarizes all major cell types in the antennal lobe, and this effect is blocked by picrotoxin or by transgenic RNAi-mediated knockdown of the GluClα gene, which encodes a glutamate-gated chloride channel. Moreover, antennal lobe neurons are inhibited by selective activation of glutamatergic local neurons using a nonnative genetically encoded cation channel. Finally, transgenic knockdown of GluClα in principal neurons disinhibits the odor responses of these neurons. Thus, glutamate acts as an inhibitory neurotransmitter in the antennal lobe, broadly similar to the role of GABA in this circuit. However, because glutamate release is concentrated between glomeruli, whereas GABA release is concentrated within glomeruli, these neurotransmitters may act on different spatial and temporal scales. Thus, the existence of two parallel inhibitory transmitter systems may increase the range and flexibility of synaptic inhibition.
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Eddison M, Belay AT, Sokolowski MB, Heberlein U. A genetic screen for olfactory habituation mutations in Drosophila: analysis of novel foraging alleles and an underlying neural circuit. PLoS One 2012; 7:e51684. [PMID: 23284741 PMCID: PMC3524188 DOI: 10.1371/journal.pone.0051684] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 11/05/2012] [Indexed: 02/07/2023] Open
Abstract
Habituation is a form of non-associative learning that enables animals to reduce their reaction to repeated harmless stimuli. When exposed to ethanol vapor, Drosophila show an olfactory-mediated startle response characterized by a transient increase in locomotor activity. Upon repeated exposures, this olfactory startle attenuates with the characteristics of habituation. Here we describe the results of a genetic screen to identify olfactory startle habituation (OSH) mutants. One mutation is a transcript specific allele of foraging (for) encoding a cGMP-dependent kinase. We show this allele of for reduces expression of a for-T1 isoform expressed in the head and functions normally to inhibit OSH. We localize for-T1 function to a limited set of neurons that include olfactory receptor neurons (ORNs) and the mushroom body (MB). Overexpression of for-T1 in ORNs inhibits OSH, an effect also seen upon synaptic silencing of the ORNs; for-T1 may therefore function in ORNs to decrease synaptic release upon repeated exposure to ethanol vapor. Overall, this work contributes to our understanding of the genes and neurons underlying olfactory habituation in Drosophila.
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Affiliation(s)
- Mark Eddison
- Department of Anatomy, University of California San Francisco, San Francisco, CA, USA.
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Paranjpe P, Rodrigues V, VijayRaghavan K, Ramaswami M. Gustatory habituation in Drosophila relies on rutabaga (adenylate cyclase)-dependent plasticity of GABAergic inhibitory neurons. Learn Mem 2012; 19:627-35. [DOI: 10.1101/lm.026641.112] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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