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Chen R, Wang Z, Lin Q, Hou X, Jiang Y, Le Q, Liu X, Ma L, Wang F. Destabilization of fear memory by Rac1-driven engram-microglia communication in hippocampus. Brain Behav Immun 2024; 119:621-636. [PMID: 38670239 DOI: 10.1016/j.bbi.2024.04.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 04/19/2024] [Accepted: 04/22/2024] [Indexed: 04/28/2024] Open
Abstract
Rac1 is a key regulator of the cytoskeleton and neuronal plasticity, and is known to play a critical role in psychological and cognitive brain disorders. To elucidate the engram specific Rac1 signaling in fear memory, a doxycycline (Dox)-dependent robust activity marking (RAM) system was used to label dorsal dentate gyrus (DG) engram cells in mice during contextual fear conditioning. Rac1 mRNA and protein levels in DG engram cells were peaked at 24 h (day 1) after fear conditioning and were more abundant in the fear engram cells than in the non-engram cells. Optogenetic activation of Rac1 in a temporal manner in DG engram cells before memory retrieval decreased the freezing level in the fear context. Optogenetic activation of Rac1 increased autophagy protein 7 (ATG7) expression in the DG engram cells and activated DG microglia. Microglia-specific transcriptomics and fluorescence in situ hybridization revealed that overexpression of ATG7 in the fear engram cells upregulated the mRNA of Toll-like receptor TLR2/4 in DG microglia. Knockdown of microglial TLR2/4 rescued fear memory destabilization induced by ATG7 overexpression or Rac1 activation in DG engram cells. These results indicate that Rac1-driven communications between engram cells and microglia contributes to contextual fear memory destabilization, and is mediated by ATG7 and TLR2/4, and suggest a novel mechanistic framework for the cytoskeletal regulator in fear memory interference.
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Affiliation(s)
- Ruyan Chen
- School of Basic Medicine Sciences, State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Pharmacology Research Center, Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200032, China; Research Unit of Addition Memory, Chinese Academy of Medical Sciences (2021RU009), Shanghai 200032, China
| | - Zhilin Wang
- School of Basic Medicine Sciences, State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Pharmacology Research Center, Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200032, China; Research Unit of Addition Memory, Chinese Academy of Medical Sciences (2021RU009), Shanghai 200032, China
| | - Qing Lin
- School of Basic Medicine Sciences, State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Pharmacology Research Center, Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200032, China; Research Unit of Addition Memory, Chinese Academy of Medical Sciences (2021RU009), Shanghai 200032, China
| | - Xutian Hou
- School of Basic Medicine Sciences, State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Pharmacology Research Center, Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200032, China; Research Unit of Addition Memory, Chinese Academy of Medical Sciences (2021RU009), Shanghai 200032, China
| | - Yan Jiang
- School of Basic Medicine Sciences, State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Pharmacology Research Center, Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200032, China; Research Unit of Addition Memory, Chinese Academy of Medical Sciences (2021RU009), Shanghai 200032, China
| | - Qiumin Le
- School of Basic Medicine Sciences, State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Pharmacology Research Center, Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200032, China; Research Unit of Addition Memory, Chinese Academy of Medical Sciences (2021RU009), Shanghai 200032, China
| | - Xing Liu
- School of Basic Medicine Sciences, State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Pharmacology Research Center, Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200032, China; Research Unit of Addition Memory, Chinese Academy of Medical Sciences (2021RU009), Shanghai 200032, China
| | - Lan Ma
- School of Basic Medicine Sciences, State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Pharmacology Research Center, Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200032, China; Research Unit of Addition Memory, Chinese Academy of Medical Sciences (2021RU009), Shanghai 200032, China
| | - Feifei Wang
- School of Basic Medicine Sciences, State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Pharmacology Research Center, Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200032, China; Research Unit of Addition Memory, Chinese Academy of Medical Sciences (2021RU009), Shanghai 200032, China.
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2
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Dwijesha AS, Eswaran A, Berry JA, Phan A. Diverse memory paradigms in Drosophila reveal diverse neural mechanisms. Learn Mem 2024; 31:a053810. [PMID: 38862165 PMCID: PMC11199951 DOI: 10.1101/lm.053810.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2023] [Accepted: 01/12/2024] [Indexed: 06/13/2024]
Abstract
In this review, we aggregated the different types of learning and memory paradigms developed in adult Drosophila and attempted to assess the similarities and differences in the neural mechanisms supporting diverse types of memory. The simplest association memory assays are conditioning paradigms (olfactory, visual, and gustatory). A great deal of work has been done on these memories, revealing hundreds of genes and neural circuits supporting this memory. Variations of conditioning assays (reversal learning, trace conditioning, latent inhibition, and extinction) also reveal interesting memory mechanisms, whereas mechanisms supporting spatial memory (thermal maze, orientation memory, and heat box) and the conditioned suppression of innate behaviors (phototaxis, negative geotaxis, anemotaxis, and locomotion) remain largely unexplored. In recent years, there has been an increased interest in multisensory and multicomponent memories (context-dependent and cross-modal memory) and higher-order memory (sensory preconditioning and second-order conditioning). Some of this work has revealed how the intricate mushroom body (MB) neural circuitry can support more complex memories. Finally, the most complex memories are arguably those involving social memory: courtship conditioning and social learning (mate-copying and egg-laying behaviors). Currently, very little is known about the mechanisms supporting social memories. Overall, the MBs are important for association memories of multiple sensory modalities and multisensory integration, whereas the central complex is important for place, orientation, and navigation memories. Interestingly, several different types of memory appear to use similar or variants of the olfactory conditioning neural circuitry, which are repurposed in different ways.
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Affiliation(s)
- Amoolya Sai Dwijesha
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2R3, Canada
| | - Akhila Eswaran
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2R3, Canada
| | - Jacob A Berry
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2R3, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta T6G 2R3, Canada
| | - Anna Phan
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2R3, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta T6G 2R3, Canada
- Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta T6G 2R3, Canada
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3
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Rajagopalan AE, Darshan R, Hibbard KL, Fitzgerald JE, Turner GC. Reward expectations direct learning and drive operant matching in Drosophila. Proc Natl Acad Sci U S A 2023; 120:e2221415120. [PMID: 37733736 PMCID: PMC10523640 DOI: 10.1073/pnas.2221415120] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Accepted: 08/11/2023] [Indexed: 09/23/2023] Open
Abstract
Foraging animals must use decision-making strategies that dynamically adapt to the changing availability of rewards in the environment. A wide diversity of animals do this by distributing their choices in proportion to the rewards received from each option, Herrnstein's operant matching law. Theoretical work suggests an elegant mechanistic explanation for this ubiquitous behavior, as operant matching follows automatically from simple synaptic plasticity rules acting within behaviorally relevant neural circuits. However, no past work has mapped operant matching onto plasticity mechanisms in the brain, leaving the biological relevance of the theory unclear. Here, we discovered operant matching in Drosophila and showed that it requires synaptic plasticity that acts in the mushroom body and incorporates the expectation of reward. We began by developing a dynamic foraging paradigm to measure choices from individual flies as they learn to associate odor cues with probabilistic rewards. We then built a model of the fly mushroom body to explain each fly's sequential choice behavior using a family of biologically realistic synaptic plasticity rules. As predicted by past theoretical work, we found that synaptic plasticity rules could explain fly matching behavior by incorporating stimulus expectations, reward expectations, or both. However, by optogenetically bypassing the representation of reward expectation, we abolished matching behavior and showed that the plasticity rule must specifically incorporate reward expectations. Altogether, these results reveal the first synapse-level mechanisms of operant matching and provide compelling evidence for the role of reward expectation signals in the fly brain.
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Affiliation(s)
- Adithya E. Rajagopalan
- Janelia Research Campus, HHMI, Ashburn, VA20147
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD21205
| | - Ran Darshan
- Janelia Research Campus, HHMI, Ashburn, VA20147
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Sagol School of Neuroscience, The School of Physics and Astronomy, Tel Aviv University, Tel Aviv6997801, Israel
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4
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Paoli M, Macri C, Giurfa M. A cognitive account of trace conditioning in insects. CURRENT OPINION IN INSECT SCIENCE 2023; 57:101034. [PMID: 37044245 DOI: 10.1016/j.cois.2023.101034] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 04/03/2023] [Accepted: 04/05/2023] [Indexed: 05/07/2023]
Abstract
Trace conditioning is a form of Pavlovian learning in which the conditioned stimulus (CS) and the unconditioned stimulus (US) are separated by a temporal gap. Insects learn trace associations of variable nature (appetitive, aversive) and involving CSs of different sensory modalities (olfactory, visual). The accessibility of the insect neural system in behaving animals allowed identifying neural processes driving trace conditioning: the existence of prolonged neural responses to the CS after stimulus offset and the anticipation of US responses during the free-stimulus gap. Specific brain structures, such as the mushroom bodies seem to be allocated to this learning form. Here, we posit that a further component facilitating trace conditioning in insects relates to neuromodulatory mechanisms underlying enhanced attention. We thus propose a model based on different types of mushroom-body neurons, which provides a cognitive account of trace conditioning in insects.
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Affiliation(s)
- Marco Paoli
- Centre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative (CBI), University of Toulouse, CNRS, UPS, 31062 Toulouse cedex 9, France
| | - Catherine Macri
- Centre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative (CBI), University of Toulouse, CNRS, UPS, 31062 Toulouse cedex 9, France
| | - Martin Giurfa
- Centre de Recherches sur la Cognition Animale, Centre de Biologie Intégrative (CBI), University of Toulouse, CNRS, UPS, 31062 Toulouse cedex 9, France; Institut Universitaire de France (IUF), Paris, France.
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5
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Zeng J, Li X, Zhang R, Lv M, Wang Y, Tan K, Xia X, Wan J, Jing M, Zhang X, Li Y, Yang Y, Wang L, Chu J, Li Y, Li Y. Local 5-HT signaling bi-directionally regulates the coincidence time window for associative learning. Neuron 2023; 111:1118-1135.e5. [PMID: 36706757 PMCID: PMC11152601 DOI: 10.1016/j.neuron.2022.12.034] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 10/03/2022] [Accepted: 12/30/2022] [Indexed: 01/27/2023]
Abstract
The coincidence between conditioned stimulus (CS) and unconditioned stimulus (US) is essential for associative learning; however, the mechanism regulating the duration of this temporal window remains unclear. Here, we found that serotonin (5-HT) bi-directionally regulates the coincidence time window of olfactory learning in Drosophila and affects synaptic plasticity of Kenyon cells (KCs) in the mushroom body (MB). Utilizing GPCR-activation-based (GRAB) neurotransmitter sensors, we found that KC-released acetylcholine (ACh) activates a serotonergic dorsal paired medial (DPM) neuron, which in turn provides inhibitory feedback to KCs. Physiological stimuli induce spatially heterogeneous 5-HT signals, which proportionally gate the intrinsic coincidence time windows of different MB compartments. Artificially reducing or increasing the DPM neuron-released 5-HT shortens or prolongs the coincidence window, respectively. In a sequential trace conditioning paradigm, this serotonergic neuromodulation helps to bridge the CS-US temporal gap. Altogether, we report a model circuitry for perceiving the temporal coincidence and determining the causal relationship between environmental events.
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Affiliation(s)
- Jianzhi Zeng
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing 100871, China; Institute of Molecular Physiology, Shenzhen Bay Laboratory, Shenzhen 518132, China; PKU-IDG/McGovern Institute for Brain Research, Beijing 100871, China; Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China; National Biomedical Imaging Center, Peking University, Beijing 100871, China; Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Brain Function and Disease, School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230026, Anhui, China.
| | - Xuelin Li
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing 100871, China; PKU-IDG/McGovern Institute for Brain Research, Beijing 100871, China; National Biomedical Imaging Center, Peking University, Beijing 100871, China
| | - Renzimo Zhang
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing 100871, China; PKU-IDG/McGovern Institute for Brain Research, Beijing 100871, China; Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China; National Biomedical Imaging Center, Peking University, Beijing 100871, China; Yuanpei College, Peking University, Beijing 100871, China
| | - Mingyue Lv
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing 100871, China; PKU-IDG/McGovern Institute for Brain Research, Beijing 100871, China; National Biomedical Imaging Center, Peking University, Beijing 100871, China
| | - Yipan Wang
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing 100871, China; PKU-IDG/McGovern Institute for Brain Research, Beijing 100871, China; National Biomedical Imaging Center, Peking University, Beijing 100871, China
| | - Ke Tan
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing 100871, China; PKU-IDG/McGovern Institute for Brain Research, Beijing 100871, China
| | - Xiju Xia
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing 100871, China; PKU-IDG/McGovern Institute for Brain Research, Beijing 100871, China; National Biomedical Imaging Center, Peking University, Beijing 100871, China; PKU-THU-NIBS Joint Graduate Program, Beijing 100871, China
| | - Jinxia Wan
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing 100871, China; PKU-IDG/McGovern Institute for Brain Research, Beijing 100871, China; National Biomedical Imaging Center, Peking University, Beijing 100871, China
| | - Miao Jing
- Chinese Institute for Brain Research, Beijing 102206, China
| | - Xiuning Zhang
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing 100871, China; PKU-IDG/McGovern Institute for Brain Research, Beijing 100871, China; National Biomedical Imaging Center, Peking University, Beijing 100871, China
| | - Yu Li
- School of Medicine, The Chinese University of Hong Kong, Shenzhen 518172, China
| | - Yang Yang
- Institute of Biophysics, State Key Laboratory of Brain and Cognitive Science, Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Liang Wang
- Guangdong Provincial Key Laboratory of Biomedical Optical Imaging Technology & Center for Biomedical Optics and Molecular Imaging & CAS Key Laboratory of Health Informatics, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Jun Chu
- Guangdong Provincial Key Laboratory of Biomedical Optical Imaging Technology & Center for Biomedical Optics and Molecular Imaging & CAS Key Laboratory of Health Informatics, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Yan Li
- Institute of Biophysics, State Key Laboratory of Brain and Cognitive Science, Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yulong Li
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing 100871, China; Institute of Molecular Physiology, Shenzhen Bay Laboratory, Shenzhen 518132, China; PKU-IDG/McGovern Institute for Brain Research, Beijing 100871, China; Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China; National Biomedical Imaging Center, Peking University, Beijing 100871, China; Yuanpei College, Peking University, Beijing 100871, China; PKU-THU-NIBS Joint Graduate Program, Beijing 100871, China; Chinese Institute for Brain Research, Beijing 102206, China.
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6
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Martinez-Cervantes J, Shah P, Phan A, Cervantes-Sandoval I. Higher-order unimodal olfactory sensory preconditioning in Drosophila. eLife 2022; 11:e79107. [PMID: 36129180 PMCID: PMC9566850 DOI: 10.7554/elife.79107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 09/18/2022] [Indexed: 11/22/2022] Open
Abstract
Learning and memory storage is a complex process that has proven challenging to tackle. It is likely that, in nature, the instructive value of reinforcing experiences is acquired rather than innate. The association between seemingly neutral stimuli increases the gamut of possibilities to create meaningful associations and the predictive power of moment-by-moment experiences. Here, we report physiological and behavioral evidence of olfactory unimodal sensory preconditioning in fruit flies. We show that the presentation of a pair of odors (S1 and S2) before one of them (S1) is associated with electric shocks elicits a conditional response not only to the trained odor (S1) but to the odor previously paired with it (S2). This occurs even if the S2 odor was never presented in contiguity with the aversive stimulus. In addition, we show that inhibition of the small G protein Rac1, a known forgetting regulator, facilitates the association between S1/S2 odors. These results indicate that flies can infer value to olfactory stimuli based on the previous associative structure between odors, and that inhibition of Rac1 lengthens the time window of the olfactory 'sensory buffer', allowing the establishment of associations between odors presented in sequence.
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Affiliation(s)
| | - Prachi Shah
- Department of Biology, Georgetown UniversityWashington, DCUnited States
| | - Anna Phan
- Department of Biological Sciences and Neuroscience & Mental Health Institute, University of AlbertaEdmontonCanada
| | - Isaac Cervantes-Sandoval
- Department of Biology, Georgetown UniversityWashington, DCUnited States
- Interdisciplinary Program in Neuroscience, Georgetown UniversityWashington, DCUnited States
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7
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Grover D, Chen JY, Xie J, Li J, Changeux JP, Greenspan RJ. Differential mechanisms underlie trace and delay conditioning in Drosophila. Nature 2022; 603:302-308. [PMID: 35173333 DOI: 10.1038/s41586-022-04433-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 01/13/2022] [Indexed: 12/17/2022]
Abstract
Two forms of associative learning-delay conditioning and trace conditioning-have been widely investigated in humans and higher-order mammals1. In delay conditioning, an unconditioned stimulus (for example, an electric shock) is introduced in the final moments of a conditioned stimulus (for example, a tone), with both ending at the same time. In trace conditioning, a 'trace' interval separates the conditioned stimulus and the unconditioned stimulus. Trace conditioning therefore relies on maintaining a neural representation of the conditioned stimulus after its termination (hence making distraction possible2), to learn the conditioned stimulus-unconditioned stimulus contingency3; this makes it more cognitively demanding than delay conditioning4. Here, by combining virtual-reality behaviour with neurogenetic manipulations and in vivo two-photon brain imaging, we show that visual trace conditioning and delay conditioning in Drosophila mobilize R2 and R4m ring neurons in the ellipsoid body. In trace conditioning, calcium transients during the trace interval show increased oscillations and slower declines over repeated training, and both of these effects are sensitive to distractions. Dopaminergic activity accompanies signal persistence in ring neurons, and this is decreased by distractions solely during trace conditioning. Finally, dopamine D1-like and D2-like receptor signalling in ring neurons have different roles in delay and trace conditioning; dopamine D1-like receptor 1 mediates both forms of conditioning, whereas the dopamine D2-like receptor is involved exclusively in sustaining ring neuron activity during the trace interval of trace conditioning. These observations are similar to those previously reported in mammals during arousal5, prefrontal activation6 and high-level cognitive learning7,8.
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Affiliation(s)
- Dhruv Grover
- Kavli Institute for Brain and Mind, University of California, San Diego, La Jolla, CA, USA
| | - Jen-Yung Chen
- Kavli Institute for Brain and Mind, University of California, San Diego, La Jolla, CA, USA
| | - Jiayun Xie
- Kavli Institute for Brain and Mind, University of California, San Diego, La Jolla, CA, USA
| | - Jinfang Li
- Kavli Institute for Brain and Mind, University of California, San Diego, La Jolla, CA, USA
| | - Jean-Pierre Changeux
- Kavli Institute for Brain and Mind, University of California, San Diego, La Jolla, CA, USA.,CNRS UMR 3571, Institut Pasteur, Paris, France.,College de France, Paris, France
| | - Ralph J Greenspan
- Kavli Institute for Brain and Mind, University of California, San Diego, La Jolla, CA, USA. .,Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA.
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8
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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: 44] [Impact Index Per Article: 22.0] [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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9
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Kaldun JC, Lone SR, Humbert Camps AM, Fritsch C, Widmer YF, Stein JV, Tomchik SM, Sprecher SG. Dopamine, sleep, and neuronal excitability modulate amyloid-β-mediated forgetting in Drosophila. PLoS Biol 2021; 19:e3001412. [PMID: 34613972 PMCID: PMC8523056 DOI: 10.1371/journal.pbio.3001412] [Citation(s) in RCA: 5] [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: 04/08/2021] [Revised: 10/18/2021] [Accepted: 09/14/2021] [Indexed: 11/18/2022] Open
Abstract
Alzheimer disease (AD) is one of the main causes of age-related dementia and neurodegeneration. However, the onset of the disease and the mechanisms causing cognitive defects are not well understood. Aggregation of amyloidogenic peptides is a pathological hallmark of AD and is assumed to be a central component of the molecular disease pathways. Pan-neuronal expression of Aβ42Arctic peptides in Drosophila melanogaster results in learning and memory defects. Surprisingly, targeted expression to the mushroom bodies, a center for olfactory memories in the fly brain, does not interfere with learning but accelerates forgetting. We show here that reducing neuronal excitability either by feeding Levetiracetam or silencing of neurons in the involved circuitry ameliorates the phenotype. Furthermore, inhibition of the Rac-regulated forgetting pathway could rescue the Aβ42Arctic-mediated accelerated forgetting phenotype. Similar effects are achieved by increasing sleep, a critical regulator of neuronal homeostasis. Our results provide a functional framework connecting forgetting signaling and sleep, which are critical for regulating neuronal excitability and homeostasis and are therefore a promising mechanism to modulate forgetting caused by toxic Aβ peptides.
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Affiliation(s)
- Jenifer C. Kaldun
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Shahnaz R. Lone
- Department of Biology, University of Fribourg, Fribourg, Switzerland
- Department of Animal Sciences, Central University of Punjab, Bathinda, India
| | | | - Cornelia Fritsch
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Yves F. Widmer
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Jens V. Stein
- Department of Medicine, University of Fribourg, Fribourg, Switzerland
| | - Seth M. Tomchik
- Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida, United States of America
| | - Simon G. Sprecher
- Department of Biology, University of Fribourg, Fribourg, Switzerland
- * E-mail:
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10
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Adel M, Griffith LC. The Role of Dopamine in Associative Learning in Drosophila: An Updated Unified Model. Neurosci Bull 2021; 37:831-852. [PMID: 33779893 PMCID: PMC8192648 DOI: 10.1007/s12264-021-00665-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 09/25/2020] [Indexed: 10/21/2022] Open
Abstract
Learning to associate a positive or negative experience with an unrelated cue after the presentation of a reward or a punishment defines associative learning. The ability to form associative memories has been reported in animal species as complex as humans and as simple as insects and sea slugs. Associative memory has even been reported in tardigrades [1], species that diverged from other animal phyla 500 million years ago. Understanding the mechanisms of memory formation is a fundamental goal of neuroscience research. In this article, we work on resolving the current contradictions between different Drosophila associative memory circuit models and propose an updated version of the circuit model that predicts known memory behaviors that current models do not. Finally, we propose a model for how dopamine may function as a reward prediction error signal in Drosophila, a dopamine function that is well-established in mammals but not in insects [2, 3].
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Affiliation(s)
- Mohamed Adel
- Department of Biology, Volen National Center for Complex Systems and National Center for Behavioral Genomics, Brandeis University, Waltham, MA, 02454-9110, USA.
| | - Leslie C Griffith
- Department of Biology, Volen National Center for Complex Systems and National Center for Behavioral Genomics, Brandeis University, Waltham, MA, 02454-9110, USA
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11
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Ikarashi M, Tanimoto H. Drosophila acquires seconds-scale rhythmic behavior. J Exp Biol 2021; 224:238112. [PMID: 33795422 DOI: 10.1242/jeb.242443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 03/22/2021] [Indexed: 11/20/2022]
Abstract
Detection of the temporal structure of stimuli is crucial for prediction. While perception of interval timing is relevant for immediate behavioral adaptations, it has scarcely been investigated, especially in invertebrates. Here, we examined whether the fruit fly, Drosophila melanogaster, can acquire rhythmic behavior in the range of seconds. To this end, we developed a novel temporal conditioning paradigm utilizing repeated electric shocks. Combined automatic behavioral annotation and time-frequency analysis revealed that behavioral rhythms continued after cessation of the shocks. Furthermore, we found that aging impaired interval timing. This study thus not only demonstrates the ability of insects to acquire behavioral rhythms of a few seconds, but highlights a life-course decline of temporal coordination, which is also common in mammals.
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Affiliation(s)
- Masayoshi Ikarashi
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-Ku, Sendai, 980-8577, Japan
| | - Hiromu Tanimoto
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-Ku, Sendai, 980-8577, Japan
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12
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Birch J, Ginsburg S, Jablonka E. Unlimited Associative Learning and the origins of consciousness: a primer and some predictions. BIOLOGY & PHILOSOPHY 2020; 35:56. [PMID: 33597791 PMCID: PMC7116763 DOI: 10.1007/s10539-020-09772-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 10/14/2020] [Indexed: 06/01/2023]
Abstract
Over the past two decades, Ginsburg and Jablonka have developed a novel approach to studying the evolutionary origins of consciousness: the Unlimited Associative Learning (UAL) framework. The central idea is that there is a distinctive type of learning that can serve as a transition marker for the evolutionary transition from non-conscious to conscious life. The goal of this paper is to stimulate discussion of the framework by providing a primer on its key claims (Part I) and a clear statement of its main empirical predictions (Part II).
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Affiliation(s)
- Jonathan Birch
- Centre for Philosophy of Natural and Social Science, London School of Economics and Political Science, Houghton Street, London WC2A 2AE, UK
| | - Simona Ginsburg
- Natural Science Department, The Open University of Israel, 1 University Road, 4353701 Raanana, Israel
| | - Eva Jablonka
- Centre for Philosophy of Natural and Social Science, London School of Economics and Political Science, Houghton Street, London WC2A 2AE, UK
- The Cohn Institute for the History and Philosophy of Science and Ideas, Tel Aviv University, 6934525 Ramat Aviv, Israel
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13
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Cervantes-Sandoval I, Davis RL, Berry JA. Rac1 Impairs Forgetting-Induced Cellular Plasticity in Mushroom Body Output Neurons. Front Cell Neurosci 2020; 14:258. [PMID: 33061890 PMCID: PMC7477079 DOI: 10.3389/fncel.2020.00258] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 07/24/2020] [Indexed: 12/02/2022] Open
Abstract
Active memory forgetting is a well-regulated biological process thought to be adaptive and to allow proper cognitive functions. Recent efforts have elucidated several molecular players involved in the regulation of olfactory forgetting in Drosophila, including the small G protein Rac1, the dopamine receptor DAMB, and the scaffold protein Scribble. Similarly, we recently reported that dopaminergic neurons mediate both learning- and forgetting-induced plasticity in the mushroom body output neuron MBON-γ2α′1. Two open questions remain: how does forgetting affect plasticity in other, highly plastic, mushroom body compartments and how do genes that regulate forgetting affect this cellular plasticity? Here, we show that forgetting reverses short-term synaptic depression induced by aversive conditioning in the highly plastic mushroom body output neuron MBON-γ1pedc>α/β. In addition, our results indicate that genetic tampering with normal forgetting by inhibition of small G protein Rac1 impairs restoration of depressed odor responses to learned odor by intrinsic forgetting through time passing and forgetting induced acutely by shock stimulation after conditioning or reversal learning. These data further indicate that some forms of forgetting truly erase physiological changes generated by memory encoding.
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Affiliation(s)
- Isaac Cervantes-Sandoval
- Department of Biology, Georgetown University, Washington, DC, United States.,Interdisciplinary Program in Neuroscience, Georgetown University, Washington, DC, United States
| | - Ronald L Davis
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL, United States
| | - Jacob A Berry
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL, United States
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14
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Hidalgo S, Fuenzalida-Uribe N, Molina-Mateo D, Escobar AP, Oliva C, España RA, Andrés ME, Campusano JM. Study of the release of endogenous amines in Drosophila brain in vivo in response to stimuli linked to aversive olfactory conditioning. J Neurochem 2020; 156:337-351. [PMID: 32596813 DOI: 10.1111/jnc.15109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Revised: 06/17/2020] [Accepted: 06/18/2020] [Indexed: 11/27/2022]
Abstract
A highly challenging question in neuroscience is to understand how aminergic neural circuits contribute to the planning and execution of behaviors, including the generation of olfactory memories. In this regard, electrophysiological techniques like Local Field Potential or imaging methods have been used to answer questions relevant to cell and circuit physiology in different animal models, such as the fly Drosophila melanogaster. However, these techniques do not provide information on the neurochemical identity of the circuits of interest. Different approaches including fast scan cyclic voltammetry, allow researchers to identify and quantify in a timely fashion the release of endogenous neuroactive molecules, but have been only used in in vitro Drosophila brain preparations. Here, we report a procedure to record for the first time the release of endogenous amines -dopamine, serotonin and octopamine- in adult fly brain in vivo, by fast scan cyclic voltammetry. As a proof of principle, we carried out recordings in the calyx region of the Mushroom Bodies, the brain area mainly associated to the generation of olfactory memories in flies. By using principal component regression in normalized training sets for in vivo recordings, we detect an increase in octopamine and serotonin levels in response to electric shock and olfactory cues respectively. This new approach allows the study of dynamic changes in amine neurotransmission that underlie complex behaviors in Drosophila and shed new light on the contribution of these amines to olfactory processing in this animal model.
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Affiliation(s)
- Sergio Hidalgo
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.,School of Physiology, Pharmacology and Ncxeuroscience, Faculty of Life Sciences, University of Bristol, Bristol, UK
| | - Nicolás Fuenzalida-Uribe
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Daniela Molina-Mateo
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Angélica P Escobar
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Carlos Oliva
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Rodrigo A España
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Maria Estela Andrés
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Jorge M Campusano
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro Interdisciplinario de Neurociencia UC, Santiago, Chile
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15
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Genetic dissection of active forgetting in labile and consolidated memories in Drosophila. Proc Natl Acad Sci U S A 2019; 116:21191-21197. [PMID: 31488722 PMCID: PMC6800343 DOI: 10.1073/pnas.1903763116] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Different memory components are forgotten through distinct molecular mechanisms. In Drosophila, the activation of 2 Rho GTPases (Rac1 and Cdc42), respectively, underlies the forgetting of an early labile memory (anesthesia-sensitive memory, ASM) and a form of consolidated memory (anesthesia-resistant memory, ARM). Here, we dissected the molecular mechanisms that tie Rac1 and Cdc42 to the different types of memory forgetting. We found that 2 WASP family proteins, SCAR/WAVE and WASp, act downstream of Rac1 and Cdc42 separately to regulate ASM and ARM forgetting in mushroom body neurons. Arp2/3 complex, which organizes branched actin polymerization, is a canonical downstream effector of WASP family proteins. However, we found that Arp2/3 complex is required in Cdc42/WASp-mediated ARM forgetting but not in Rac1/SCAR-mediated ASM forgetting. Instead, we identified that Rac1/SCAR may function with formin Diaphanous (Dia), a nucleator that facilitates linear actin polymerization, in ASM forgetting. The present study, complementing the previously identified Rac1/cofilin pathway that regulates actin depolymerization, suggests that Rho GTPases regulate forgetting by recruiting both actin polymerization and depolymerization pathways. Moreover, Rac1 and Cdc42 may regulate different types of memory forgetting by tapping into different actin polymerization mechanisms.
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16
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Horiuchi J. Recurrent loops: Incorporating prediction error and semantic/episodic theories into Drosophila associative memory models. GENES BRAIN AND BEHAVIOR 2019; 18:e12567. [PMID: 30891930 PMCID: PMC6900151 DOI: 10.1111/gbb.12567] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 02/27/2019] [Accepted: 03/16/2019] [Indexed: 12/01/2022]
Abstract
In 2003, Martin Heisenberg et al. presented a model of how associative memories could be encoded and stored in the insect brain. This model was extremely influential in the Drosophila memory field, but did not incorporate several important mammalian concepts, including ideas of separate episodic and semantic types of memory and prediction error hypotheses. In addition, at that time, the concept of memory traces recurrently entering and exiting the mushroom bodies, brain areas where associative memories are formed and stored, was unknown. In this review, I present a simple updated model incorporating these ideas, which may be useful for future studies.
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Affiliation(s)
- Junjiro Horiuchi
- Department of higher brain functions and dementias, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
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17
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Lüdke A, Raiser G, Nehrkorn J, Herz AVM, Galizia CG, Szyszka P. Calcium in Kenyon Cell Somata as a Substrate for an Olfactory Sensory Memory in Drosophila. Front Cell Neurosci 2018; 12:128. [PMID: 29867361 PMCID: PMC5960692 DOI: 10.3389/fncel.2018.00128] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 04/23/2018] [Indexed: 12/31/2022] Open
Abstract
Animals can form associations between temporally separated stimuli. To do so, the nervous system has to retain a neural representation of the first stimulus until the second stimulus appears. The neural substrate of such sensory stimulus memories is unknown. Here, we search for a sensory odor memory in the insect olfactory system and characterize odorant-evoked Ca2+ activity at three consecutive layers of the olfactory system in Drosophila: in olfactory receptor neurons (ORNs) and projection neurons (PNs) in the antennal lobe, and in Kenyon cells (KCs) in the mushroom body. We show that the post-stimulus responses in ORN axons, PN dendrites, PN somata, and KC dendrites are odor-specific, but they are not predictive of the chemical identity of past olfactory stimuli. However, the post-stimulus responses in KC somata carry information about the identity of previous olfactory stimuli. These findings show that the Ca2+ dynamics in KC somata could encode a sensory memory of odorant identity and thus might serve as a basis for associations between temporally separated stimuli.
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Affiliation(s)
- Alja Lüdke
- Department of Biology, Neurobiology, University of Konstanz, Konstanz, Germany
| | - Georg Raiser
- Department of Biology, Neurobiology, University of Konstanz, Konstanz, Germany
- International Max Planck Research School for Organismal Biology, Konstanz, Germany
| | - Johannes Nehrkorn
- Fakultät für Biologie, Ludwig-Maximilians-Universität München, Martinsried, Germany
- Bernstein Center for Computational Neuroscience, Munich, Germany
| | - Andreas V. M. Herz
- Fakultät für Biologie, Ludwig-Maximilians-Universität München, Martinsried, Germany
- Bernstein Center for Computational Neuroscience, Munich, Germany
| | - C. Giovanni Galizia
- Department of Biology, Neurobiology, University of Konstanz, Konstanz, Germany
| | - Paul Szyszka
- Department of Biology, Neurobiology, University of Konstanz, Konstanz, Germany
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18
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Scaplen KM, Kaun KR. Reward from bugs to bipeds: a comparative approach to understanding how reward circuits function. J Neurogenet 2017; 30:133-48. [PMID: 27328845 PMCID: PMC4926782 DOI: 10.1080/01677063.2016.1180385] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In a complex environment, animals learn from their responses to stimuli and events. Appropriate response to reward and punishment can promote survival, reproduction and increase evolutionary fitness. Interestingly, the neural processes underlying these responses are remarkably similar across phyla. In all species, dopamine is central to encoding reward and directing motivated behaviors, however, a comprehensive understanding of how circuits encode reward and direct motivated behaviors is still lacking. In part, this is a result of the sheer diversity of neurons, the heterogeneity of their responses and the complexity of neural circuits within which they are found. We argue that general features of reward circuitry are common across model organisms, and thus principles learned from invertebrate model organisms can inform research across species. In particular, we discuss circuit motifs that appear to be functionally equivalent from flies to primates. We argue that a comparative approach to studying and understanding reward circuit function provides a more comprehensive understanding of reward circuitry, and informs disorders that affect the brain’s reward circuitry.
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Affiliation(s)
- Kristin M Scaplen
- a Department of Neuroscience , Brown University , Providence , RI , USA
| | - Karla R Kaun
- a Department of Neuroscience , Brown University , Providence , RI , USA
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19
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Davis RL, Zhong Y. The Biology of Forgetting-A Perspective. Neuron 2017; 95:490-503. [PMID: 28772119 DOI: 10.1016/j.neuron.2017.05.039] [Citation(s) in RCA: 153] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 05/26/2017] [Accepted: 05/30/2017] [Indexed: 01/23/2023]
Abstract
Pioneering research studies, beginning with those using Drosophila, have identified several molecular and cellular mechanisms for active forgetting. The currently known mechanisms for active forgetting include neurogenesis-based forgetting, interference-based forgetting, and intrinsic forgetting, the latter term describing the brain's chronic signaling systems that function to slowly degrade molecular and cellular memory traces. The best-characterized pathway for intrinsic forgetting includes "forgetting cells" that release dopamine onto engram cells, mobilizing a signaling pathway that terminates in the activation of Rac1/Cofilin to effect changes in the actin cytoskeleton and neuron/synapse structure. Intrinsic forgetting may be the default state of the brain, constantly promoting memory erasure and competing with processes that promote memory stability like consolidation. A better understanding of active forgetting will provide insights into the brain's memory management system and human brain disorders that alter active forgetting mechanisms.
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Affiliation(s)
- Ronald L Davis
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL, USA.
| | - Yi Zhong
- Tsinghua-Peking Center for Life Sciences, School for Life Sciences, Tsinghua University, Beijing, China.
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20
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Dylla KV, Raiser G, Galizia CG, Szyszka P. Trace Conditioning in Drosophila Induces Associative Plasticity in Mushroom Body Kenyon Cells and Dopaminergic Neurons. Front Neural Circuits 2017; 11:42. [PMID: 28676744 PMCID: PMC5476701 DOI: 10.3389/fncir.2017.00042] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 05/29/2017] [Indexed: 02/04/2023] Open
Abstract
Dopaminergic neurons (DANs) signal punishment and reward during associative learning. In mammals, DANs show associative plasticity that correlates with the discrepancy between predicted and actual reinforcement (prediction error) during classical conditioning. Also in insects, such as Drosophila, DANs show associative plasticity that is, however, less understood. Here, we study associative plasticity in DANs and their synaptic partners, the Kenyon cells (KCs) in the mushroom bodies (MBs), while training Drosophila to associate an odorant with a temporally separated electric shock (trace conditioning). In most MB compartments DANs strengthened their responses to the conditioned odorant relative to untrained animals. This response plasticity preserved the initial degree of similarity between the odorant- and the shock-induced spatial response patterns, which decreased in untrained animals. Contrary to DANs, KCs (α'/β'-type) decreased their responses to the conditioned odorant relative to untrained animals. We found no evidence for prediction error coding by DANs during conditioning. Rather, our data supports the hypothesis that DAN plasticity encodes conditioning-induced changes in the odorant's predictive power.
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Affiliation(s)
- Kristina V Dylla
- Department of Biology, Neurobiology, University of KonstanzKonstanz, Germany
| | - Georg Raiser
- Department of Biology, Neurobiology, University of KonstanzKonstanz, Germany
| | - C Giovanni Galizia
- Department of Biology, Neurobiology, University of KonstanzKonstanz, Germany
| | - Paul Szyszka
- Department of Biology, Neurobiology, University of KonstanzKonstanz, Germany
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21
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Zhang X, Li Q, Wang L, Liu ZJ, Zhong Y. Cdc42-Dependent Forgetting Regulates Repetition Effect in Prolonging Memory Retention. Cell Rep 2016; 16:817-25. [PMID: 27396329 DOI: 10.1016/j.celrep.2016.06.041] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 04/29/2016] [Accepted: 06/07/2016] [Indexed: 11/30/2022] Open
Abstract
Repeated learning is used daily and is a powerful way to improve memory. A fundamental question is how multiple learning trials add up to improve memory. While the major studies so far of such a repetition effect have emphasized the strengthening of memory formation, the current study reveals a molecular mechanism through suppression of forgetting. We find that single-session training leads to formation of anesthesia-resistant memory (ARM) and then activation of the small G protein Cdc42 to cause decay or forgetting of ARM within 24 hr. Repetition suppresses the activation of Cdc42-dependent forgetting, instead of enhancing ARM formation, leading to prolonged ARM. Consistently, inhibition of Cdc42 activity through genetic manipulation mimicked the repetition effect, while repetition-induced ARM improvement was abolished by elevated Cdc42 activity. Thus, only the first session in repetitive training contributes to ARM formation, while the subsequent sessions are devoted not to acquiring information but to inhibiting forgetting.
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Affiliation(s)
- Xuchen Zhang
- Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, MOE Key Laboratory of Protein Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Qian Li
- Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, MOE Key Laboratory of Protein Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Lianzhang Wang
- Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, MOE Key Laboratory of Protein Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Zhong-Jian Liu
- Shenzhen Key Laboratory for Orchid Conservation and Utilization, The National Orchid Conservation Center of China and The Orchid Conservation & Research Center of Shenzhen, Shenzhen 518114, China; The Center for Biotechnology and Biomedicine, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Yi Zhong
- Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, MOE Key Laboratory of Protein Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
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22
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Sunouchi K, Koganezawa M, Yamamoto D. REQUIREMENT OF THE TEC FAMILY TYROSINE KINASE BTK29A FOR COURTSHIP MEMORY IN Drosophila MALES. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2016; 91:165-174. [PMID: 26782301 DOI: 10.1002/arch.21316] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A male Drosophila that is not successful in courtship will reduce his courtship efforts in the next encounter with a female. This courtship suppression persists for more than 1 h in wild-type males. The Btk29A(ficP) mutant males null for the Btk29A type 2 isoform, a fly homolog of the nonreceptor tyrosine kinase Btk, show no courtship suppression, while Btk29A hypomorphic males exhibit a rapid decline in courtship suppression, leading to its complete loss within 30 min. The males of a revertant stock or Btk29A(ficP) males that are also mutant for parkas, a gene encoding the presumptive negative regulator of Btk29A, exhibit normal courtship suppression. Since another behavioral assay has shown that Btk29A(ficP) mutants are sensitization-defective, we hypothesize that the mutant flies are unable to maintain the neural excitation state acquired by experience, resulting in the rapid loss of courtship suppression.
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Affiliation(s)
- Kazuya Sunouchi
- Division of Neurogenetics, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Masayuki Koganezawa
- Division of Neurogenetics, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Daisuke Yamamoto
- Division of Neurogenetics, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
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23
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Dissecting neural pathways for forgetting in Drosophila olfactory aversive memory. Proc Natl Acad Sci U S A 2015; 112:E6663-72. [PMID: 26627257 DOI: 10.1073/pnas.1512792112] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recent studies have identified molecular pathways driving forgetting and supported the notion that forgetting is a biologically active process. The circuit mechanisms of forgetting, however, remain largely unknown. Here we report two sets of Drosophila neurons that account for the rapid forgetting of early olfactory aversive memory. We show that inactivating these neurons inhibits memory decay without altering learning, whereas activating them promotes forgetting. These neurons, including a cluster of dopaminergic neurons (PAM-β'1) and a pair of glutamatergic neurons (MBON-γ4>γ1γ2), terminate in distinct subdomains in the mushroom body and represent parallel neural pathways for regulating forgetting. Interestingly, although activity of these neurons is required for memory decay over time, they are not required for acute forgetting during reversal learning. Our results thus not only establish the presence of multiple neural pathways for forgetting in Drosophila but also suggest the existence of diverse circuit mechanisms of forgetting in different contexts.
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24
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Vogt K, Yarali A, Tanimoto H. Reversing Stimulus Timing in Visual Conditioning Leads to Memories with Opposite Valence in Drosophila. PLoS One 2015; 10:e0139797. [PMID: 26430885 PMCID: PMC4592196 DOI: 10.1371/journal.pone.0139797] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 09/17/2015] [Indexed: 11/18/2022] Open
Abstract
Animals need to associate different environmental stimuli with each other regardless of whether they temporally overlap or not. Drosophila melanogaster displays olfactory trace conditioning, where an odor is followed by electric shock reinforcement after a temporal gap, leading to conditioned odor avoidance. Reversing the stimulus timing in olfactory conditioning results in the reversal of memory valence such that an odor that follows shock is later on approached (i.e. relief conditioning). Here, we explored the effects of stimulus timing on memory in another sensory modality, using a visual conditioning paradigm. We found that flies form visual memories of opposite valence depending on stimulus timing and can associate a visual stimulus with reinforcement despite being presented with a temporal gap. These results suggest that associative memories with non-overlapping stimuli and the effect of stimulus timing on memory valence are shared across sensory modalities.
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Affiliation(s)
- Katrin Vogt
- Max Planck Institute of Neurobiology, 82152, Martinsried, Germany
| | - Ayse Yarali
- Max Planck Institute of Neurobiology, 82152, Martinsried, Germany
- Leibniz Institute for Neurobiology (LIN), Research Group Molecular Systems Biology of Learning, 39118, Magdeburg, Germany
- Center for Behavioral Brain Sciences, 39118, Magdeburg, Germany
| | - Hiromu Tanimoto
- Max Planck Institute of Neurobiology, 82152, Martinsried, Germany
- Tohoku University Graduate School of Life Sciences, 980–8577, Sendai, Japan
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25
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Hawkins RD, Byrne JH. Associative learning in invertebrates. Cold Spring Harb Perspect Biol 2015; 7:cshperspect.a021709. [PMID: 25877219 DOI: 10.1101/cshperspect.a021709] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
This work reviews research on neural mechanisms of two types of associative learning in the marine mollusk Aplysia, classical conditioning of the gill- and siphon-withdrawal reflex and operant conditioning of feeding behavior. Basic classical conditioning is caused in part by activity-dependent facilitation at sensory neuron-motor neuron (SN-MN) synapses and involves a hybrid combination of activity-dependent presynaptic facilitation and Hebbian potentiation, which are coordinated by trans-synaptic signaling. Classical conditioning also shows several higher-order features, which might be explained by the known circuit connections in Aplysia. Operant conditioning is caused in part by a different type of mechanism, an intrinsic increase in excitability of an identified neuron in the central pattern generator (CPG) for feeding. However, for both classical and operant conditioning, adenylyl cyclase is a molecular site of convergence of the two signals that are associated. Learning in other invertebrate preparations also involves many of the same mechanisms, which may contribute to learning in vertebrates as well.
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Affiliation(s)
- Robert D Hawkins
- Department of Neuroscience, Columbia University, New York, New York 10032 New York State Psychiatric Institute, New York, New York 10032
| | - John H Byrne
- Department of Neurobiology and Anatomy, The University of Texas Medical School at Houston, Houston, Texas 77030
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26
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Lamprecht R. The actin cytoskeleton in memory formation. Prog Neurobiol 2014; 117:1-19. [DOI: 10.1016/j.pneurobio.2014.02.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 02/02/2014] [Accepted: 02/03/2014] [Indexed: 01/21/2023]
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27
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Dylla KV, Galili DS, Szyszka P, Lüdke A. Trace conditioning in insects-keep the trace! Front Physiol 2013; 4:67. [PMID: 23986710 PMCID: PMC3750952 DOI: 10.3389/fphys.2013.00067] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 03/17/2013] [Indexed: 11/13/2022] Open
Abstract
Trace conditioning is a form of associative learning that can be induced by presenting a conditioned stimulus (CS) and an unconditioned stimulus (US) following each other, but separated by a temporal gap. This gap distinguishes trace conditioning from classical delay conditioning, where the CS and US overlap. To bridge the temporal gap between both stimuli and to form an association between CS and US in trace conditioning, the brain must keep a neural representation of the CS after its termination-a stimulus trace. Behavioral and physiological studies on trace and delay conditioning revealed similarities between the two forms of learning, like similar memory decay and similar odor identity perception in invertebrates. On the other hand differences were reported also, like the requirement of distinct brain structures in vertebrates or disparities in molecular mechanisms in both vertebrates and invertebrates. For example, in commonly used vertebrate conditioning paradigms the hippocampus is necessary for trace but not for delay conditioning, and Drosophila delay conditioning requires the Rutabaga adenylyl cyclase (Rut-AC), which is dispensable in trace conditioning. It is still unknown how the brain encodes CS traces and how they are associated with a US in trace conditioning. Insects serve as powerful models to address the mechanisms underlying trace conditioning, due to their simple brain anatomy, behavioral accessibility and established methods of genetic interference. In this review we summarize the recent progress in insect trace conditioning on the behavioral and physiological level and emphasize similarities and differences compared to delay conditioning. Moreover, we examine proposed molecular and computational models and reassess different experimental approaches used for trace conditioning.
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Affiliation(s)
- Kristina V. Dylla
- Department of Biology, Neurobiology, University of KonstanzKonstanz, Germany
| | - Dana S. Galili
- Behavioral Genetics, Max-Planck Institute for NeurobiologyMartinsried, Germany
| | - Paul Szyszka
- Department of Biology, Neurobiology, University of KonstanzKonstanz, Germany
| | - Alja Lüdke
- Department of Biology, Neurobiology, University of KonstanzKonstanz, Germany
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Guttridge TL, Brown C. Learning and memory in the Port Jackson shark, Heterodontus portusjacksoni. Anim Cogn 2013; 17:415-25. [DOI: 10.1007/s10071-013-0673-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 08/01/2013] [Accepted: 08/07/2013] [Indexed: 02/03/2023]
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Dubnau J, Chiang AS. Systems memory consolidation in Drosophila. Curr Opin Neurobiol 2013; 23:84-91. [DOI: 10.1016/j.conb.2012.09.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 09/25/2012] [Indexed: 10/27/2022]
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Drosophila Memory Research through Four Eras. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/b978-0-12-415823-8.00027-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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31
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Shmookler Reis RJ. Coming to terms with complexity: limits to a reductionist view of aging. Front Genet 2012; 3:149. [PMID: 22969788 PMCID: PMC3427912 DOI: 10.3389/fgene.2012.00149] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Accepted: 07/26/2012] [Indexed: 11/17/2022] Open
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Tissue-specific activation of a single gustatory receptor produces opposing behavioral responses in Drosophila. Genetics 2012; 192:521-32. [PMID: 22798487 PMCID: PMC3454881 DOI: 10.1534/genetics.112.142455] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Understanding sensory systems that perceive environmental inputs and neural circuits that select appropriate motor outputs is essential for studying how organisms modulate behavior and make decisions necessary for survival. Drosophila melanogaster oviposition is one such important behavior, in which females evaluate their environment and choose to lay eggs on substrates they may find aversive in other contexts. We employed neurogenetic techniques to characterize neurons that influence the choice between repulsive positional and attractive egg-laying responses toward the bitter-tasting compound lobeline. Surprisingly, we found that neurons expressing Gr66a, a gustatory receptor normally involved in avoidance behaviors, receive input for both attractive and aversive preferences. We hypothesized that these opposing responses may result from activation of distinct Gr66a-expressing neurons. Using tissue-specific rescue experiments, we found that Gr66a-expressing neurons on the legs mediate positional aversion. In contrast, pharyngeal taste cells mediate the egg-laying attraction to lobeline, as determined by analysis of mosaic flies in which subsets of Gr66a neurons were silenced. Finally, inactivating mushroom body neurons disrupted both aversive and attractive responses, suggesting that this brain structure is a candidate integration center for decision-making during Drosophila oviposition. We thus define sensory and central neurons critical to the process by which flies decide where to lay an egg. Furthermore, our findings provide insights into the complex nature of gustatory perception in Drosophila. We show that tissue-specific activation of bitter-sensing Gr66a neurons provides one mechanism by which the gustatory system differentially encodes aversive and attractive responses, allowing the female fly to modulate her behavior in a context-dependent manner.
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Yarali A, Nehrkorn J, Tanimoto H, Herz AVM. Event timing in associative learning: from biochemical reaction dynamics to behavioural observations. PLoS One 2012; 7:e32885. [PMID: 22493657 PMCID: PMC3316544 DOI: 10.1371/journal.pone.0032885] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Accepted: 02/05/2012] [Indexed: 11/18/2022] Open
Abstract
Associative learning relies on event timing. Fruit flies for example, once trained with an odour that precedes electric shock, subsequently avoid this odour (punishment learning); if, on the other hand the odour follows the shock during training, it is approached later on (relief learning). During training, an odour-induced Ca++ signal and a shock-induced dopaminergic signal converge in the Kenyon cells, synergistically activating a Ca++-calmodulin-sensitive adenylate cyclase, which likely leads to the synaptic plasticity underlying the conditioned avoidance of the odour. In Aplysia, the effect of serotonin on the corresponding adenylate cyclase is bi-directionally modulated by Ca++, depending on the relative timing of the two inputs. Using a computational approach, we quantitatively explore this biochemical property of the adenylate cyclase and show that it can generate the effect of event timing on associative learning. We overcome the shortage of behavioural data in Aplysia and biochemical data in Drosophila by combining findings from both systems.
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Affiliation(s)
- Ayse Yarali
- Max Planck Institute of Neurobiology, Martinsried, Germany.
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