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Park S, Ko SY, Frankland PW, Josselyn SA. Comparing behaviours induced by natural memory retrieval and optogenetic reactivation of an engram ensemble in mice. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230227. [PMID: 38853560 DOI: 10.1098/rstb.2023.0227] [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: 11/14/2023] [Accepted: 04/09/2024] [Indexed: 06/11/2024] Open
Abstract
Memories are thought to be stored within sparse collections of neurons known as engram ensembles. Neurons active during a training episode are allocated to an engram ensemble ('engram neurons'). Memory retrieval is initiated by external sensory or internal cues present at the time of training reactivating engram neurons. Interestingly, optogenetic reactivation of engram ensemble neurons alone in the absence of external sensory cues is sufficient to induce behaviour consistent with memory retrieval in mice. However, there may exist differences between the behaviours induced by natural retrieval cues or artificial engram reactivation. Here, we compared two defensive behaviours (freezing and the syllable structure of ultrasonic vocalizations, USVs) induced by sensory cues present at training (natural memory retrieval) and optogenetic engram ensemble reactivation (artificial memory retrieval) in a threat conditioning paradigm in the same mice. During natural memory recall, we observed a strong positive correlation between freezing levels and distinct USV syllable features (characterized by an unsupervised algorithm, MUPET (Mouse Ultrasonic Profile ExTraction)). Moreover, we observed strikingly similar behavioural profiles in terms of freezing and USV characteristics between natural memory recall and artificial memory recall in the absence of sensory retrieval cues. Although our analysis focused on two behavioural measures of threat memory (freezing and USV characteristics), these results underscore the similarities between threat memory recall triggered naturally and through optogenetic reactivation of engram ensembles. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.
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Affiliation(s)
- Sungmo Park
- Program in Neurosciences and Mental Health, Hospital for Sick Children, 555 University Avenue , Toronto, Ontario M5G 1X8, Canada
| | - Sang Yoon Ko
- Program in Neurosciences and Mental Health, Hospital for Sick Children, 555 University Avenue , Toronto, Ontario M5G 1X8, Canada
- Department of Physiology, University of Toronto , Toronto, Ontario M5G 1X8, Canada
| | - Paul W Frankland
- Program in Neurosciences and Mental Health, Hospital for Sick Children, 555 University Avenue , Toronto, Ontario M5G 1X8, Canada
- Department of Physiology, University of Toronto , Toronto, Ontario M5G 1X8, Canada
- Department of Psychology, University of Toronto , Toronto, Ontario M5G 1X8, Canada
| | - Sheena A Josselyn
- Program in Neurosciences and Mental Health, Hospital for Sick Children, 555 University Avenue , Toronto, Ontario M5G 1X8, Canada
- Department of Physiology, University of Toronto , Toronto, Ontario M5G 1X8, Canada
- Department of Psychology, University of Toronto , Toronto, Ontario M5G 1X8, Canada
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2
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Antonoudiou P, Stone BT, Colmers PLW, Evans-Strong A, Teboul E, Walton NL, Weiss GL, Maguire J. Experience-dependent information routing through the basolateral amygdala shapes behavioral outcomes. Cell Rep 2024; 43:114489. [PMID: 38990724 DOI: 10.1016/j.celrep.2024.114489] [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: 11/06/2023] [Revised: 05/22/2024] [Accepted: 06/25/2024] [Indexed: 07/13/2024] Open
Abstract
It is well established that the basolateral amygdala (BLA) is an emotional processing hub that governs a diverse repertoire of behaviors. Selective engagement of a heterogeneous cell population in the BLA is thought to contribute to this flexibility in behavioral outcomes. However, whether this process is impacted by previous experiences that influence emotional processing remains unclear. Here we demonstrate that previous positive (enriched environment [EE]) or negative (chronic unpredictable stress [CUS]) experiences differentially influence the activity of populations of BLA principal neurons projecting to either the nucleus accumbens core or bed nucleus of the stria terminalis. Chemogenetic manipulation of these projection-specific neurons can mimic or occlude the effects of CUS and EE on behavioral outcomes to bidirectionally control avoidance behaviors and stress-induced helplessness. These data demonstrate that previous experiences influence the responsiveness of projection-specific BLA principal neurons, biasing information routing through the BLA, to drive divergent behavioral outcomes.
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Affiliation(s)
- Pantelis Antonoudiou
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Bradly T Stone
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Phillip L W Colmers
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Aidan Evans-Strong
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Eric Teboul
- Neuroscience Program, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA, USA
| | - Najah L Walton
- Neuroscience Program, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA, USA
| | - Grant L Weiss
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Jamie Maguire
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA.
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3
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Casanova JP, Pouget C, Treiber N, Agarwal I, Brimble MA, Vetere G. Threat-dependent scaling of prelimbic dynamics to enhance fear representation. Neuron 2024; 112:2304-2314.e6. [PMID: 38772375 DOI: 10.1016/j.neuron.2024.04.029] [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: 10/25/2023] [Revised: 03/01/2024] [Accepted: 04/24/2024] [Indexed: 05/23/2024]
Abstract
Promptly identifying threatening stimuli is crucial for survival. Freezing is a natural behavior displayed by rodents toward potential or actual threats. Although it is known that the prelimbic cortex (PL) is involved in both risk evaluation and in fear and anxiety-like behavior expression, here we explored whether PL neuronal activity can dynamically represent different internal states of the same behavioral output (i.e., freezing). We found that freezing can always be decoded from PL activity at a population level. However, the sudden presentation of a fearful stimulus quickly reshaped the PL to a new neuronal activity state, an effect not observed in other cortical or subcortical regions examined. This shift changed PL freezing representation and is necessary for fear memory expression. Our data reveal the unique role of the PL in detecting threats and internally adjusting to distinguish between different freezing-related states in both unconditioned and conditioned fear representations.
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Affiliation(s)
- José Patricio Casanova
- Cerebral Codes and Circuits Connectivity team, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, 10 rue Vauquelin, 75005 Paris, France
| | - Clément Pouget
- Cerebral Codes and Circuits Connectivity team, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, 10 rue Vauquelin, 75005 Paris, France
| | - Nadja Treiber
- Cerebral Codes and Circuits Connectivity team, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, 10 rue Vauquelin, 75005 Paris, France
| | - Ishaant Agarwal
- Cerebral Codes and Circuits Connectivity team, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, 10 rue Vauquelin, 75005 Paris, France
| | - Mark Allen Brimble
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Gisella Vetere
- Cerebral Codes and Circuits Connectivity team, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, 10 rue Vauquelin, 75005 Paris, France.
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4
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Shakhawat AMD, Foltz JG, Nance AB, Bhateja J, Raymond JL. Systemic pharmacological suppression of neural activity reverses learning impairment in a mouse model of Fragile X syndrome. eLife 2024; 12:RP92543. [PMID: 38953282 PMCID: PMC11219043 DOI: 10.7554/elife.92543] [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: 07/03/2024] Open
Abstract
The enhancement of associative synaptic plasticity often results in impaired rather than enhanced learning. Previously, we proposed that such learning impairments can result from saturation of the plasticity mechanism (Nguyen-Vu et al., 2017), or, more generally, from a history-dependent change in the threshold for plasticity. This hypothesis was based on experimental results from mice lacking two class I major histocompatibility molecules, MHCI H2-Kb and H2-Db (MHCI KbDb-/-), which have enhanced associative long-term depression at the parallel fiber-Purkinje cell synapses in the cerebellum (PF-Purkinje cell LTD). Here, we extend this work by testing predictions of the threshold metaplasticity hypothesis in a second mouse line with enhanced PF-Purkinje cell LTD, the Fmr1 knockout mouse model of Fragile X syndrome (FXS). Mice lacking Fmr1 gene expression in cerebellar Purkinje cells (L7-Fmr1 KO) were selectively impaired on two oculomotor learning tasks in which PF-Purkinje cell LTD has been implicated, with no impairment on LTD-independent oculomotor learning tasks. Consistent with the threshold metaplasticity hypothesis, behavioral pre-training designed to reverse LTD at the PF-Purkinje cell synapses eliminated the oculomotor learning deficit in the L7-Fmr1 KO mice, as previously reported in MHCI KbDb-/-mice. In addition, diazepam treatment to suppress neural activity and thereby limit the induction of associative LTD during the pre-training period also eliminated the learning deficits in L7-Fmr1 KO mice. These results support the hypothesis that cerebellar LTD-dependent learning is governed by an experience-dependent sliding threshold for plasticity. An increased threshold for LTD in response to elevated neural activity would tend to oppose firing rate stability, but could serve to stabilize synaptic weights and recently acquired memories. The metaplasticity perspective could inform the development of new clinical approaches for addressing learning impairments in autism and other disorders of the nervous system.
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Affiliation(s)
- Amin MD Shakhawat
- Department of Neurobiology, Stanford UniversityStanfordUnited States
| | | | - Adam B Nance
- Department of Neurobiology, Stanford UniversityStanfordUnited States
| | - Jaydev Bhateja
- Department of Neurobiology, Stanford UniversityStanfordUnited States
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5
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Santos TB, de Oliveira Coelho CA, Kramer-Soares JC, Frankland PW, Oliveira MGM. Reactivation of encoding ensembles in the prelimbic cortex supports temporal associations. Neuropsychopharmacology 2024; 49:1296-1308. [PMID: 38454052 PMCID: PMC11224261 DOI: 10.1038/s41386-024-01825-2] [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: 10/12/2023] [Revised: 01/14/2024] [Accepted: 02/05/2024] [Indexed: 03/09/2024]
Abstract
Fear conditioning is encoded by strengthening synaptic connections between the neurons activated by a conditioned stimulus (CS) and those activated by an unconditioned stimulus (US), forming a memory engram, which is reactivated during memory retrieval. In temporal associations, activity within the prelimbic cortex (PL) plays a role in sustaining a short-term, transient memory of the CS, which is associated with the US after a temporal gap. However, it is unknown whether the PL has only a temporary role, transiently representing the CS, or is part of the neuronal ensembles that support the retrieval, i.e., whether PL neurons support both transient, short-term memories and stable, long-term memories. We investigated neuronal ensembles underlying temporal associations using fear conditioning with a 5-s interval between the CS and US (CFC-5s). Controls were trained in contextual fear conditioning (CFC), in which the CS-US overlaps. We used Robust Activity Marking (RAM) to selectively manipulate PL neurons activated by CFC-5s learning and Targeted Recombination in Active Populations (TRAP2) mice to label neurons activated by CFC-5s learning and reactivated by memory retrieval in the amygdala, medial prefrontal cortex, hippocampus, perirhinal cortices (PER) and subiculum. We also computed their co-reactivation to generate correlation-based networks. The optogenetic reactivation or silencing of PL encoding ensembles either promoted or impaired the retrieval of CFC-5s but not CFC. CFC-5s retrieval reactivated encoding ensembles in the PL, PER, and basolateral amygdala. The engram network of CFC-5s had higher amygdala and PER centralities and interconnectivity. The same PL neurons support learning and stable associative memories.
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Affiliation(s)
- Thays Brenner Santos
- Departamento de Psicobiologia, Universidade Federal de São Paulo - UNIFESP, São Paulo, 04023-062, Brazil.
| | | | - Juliana Carlota Kramer-Soares
- Departamento de Psicobiologia, Universidade Federal de São Paulo - UNIFESP, São Paulo, 04023-062, Brazil
- Universidade Cruzeiro do Sul - UNICSUL, São Paulo, 08060-070, Brazil
| | - Paul W Frankland
- Neuroscience and Mental Health, Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada
- Department of Physiology, University of Toronto, Toronto, ON, M5G 1X8, Canada
- Department of Psychology, University of Toronto, Toronto, ON, M5G 1X8, Canada
- Institute of Medical Sciences, University of Toronto, Toronto, ON, M5G 1X8, Canada
- Child & Brain Development Program, Canadian Institute for Advanced Research, Toronto, ON, M5G 1M1, Canada
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6
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Luft JG, Popik B, Gonçalves DA, Cruz FC, de Oliveira Alvares L. Distinct engrams control fear and extinction memory. Hippocampus 2024; 34:230-240. [PMID: 38396226 DOI: 10.1002/hipo.23601] [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: 09/20/2023] [Revised: 12/06/2023] [Accepted: 02/04/2024] [Indexed: 02/25/2024]
Abstract
Memories are stored in engram cells, which are necessary and sufficient for memory recall. Recalling a memory might undergo reconsolidation or extinction. It has been suggested that the original memory engram is reactivated during reconsolidation so that memory can be updated. Conversely, during extinction training, a new memory is formed that suppresses the original engram. Nonetheless, it is unknown whether extinction creates a new engram or modifies the original fear engram. In this study, we utilized the Daun02 procedure, which uses c-Fos-lacZ rats to induce apoptosis of strongly activated neurons and examine whether a new memory trace emerges as a result of a short or long reactivation, or if these processes rely on modifications within the original engram located in the basolateral amygdala (BLA) and infralimbic (IL) cortex. By eliminating neurons activated during consolidation and reactivation, we observed significant impacts on fear memory, highlighting the importance of the BLA engram in these processes. Although we were unable to show any impact when removing the neurons activated after the test of a previously extinguished memory in the BLA, disrupting the IL extinction engram reactivated the aversive memory that was suppressed by the extinction memory. Thus, we demonstrated that the IL cortex plays a crucial role in the network involved in extinction, and disrupting this specific node alone is sufficient to impair extinction behavior. Additionally, our findings indicate that extinction memories rely on the formation of a new memory, supporting the theory that extinction memories rely on the formation of a new memory, whereas the reconsolidation process reactivates the same original memory trace.
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Affiliation(s)
- Jordana Griebler Luft
- Laboratório de Neurobiologia da Memória, Departamento de Biofísica, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Bruno Popik
- Laboratório de Neurobiologia da Memória, Departamento de Biofísica, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Débora Aguirre Gonçalves
- Laboratório de Neurobiologia da Memória, Departamento de Biofísica, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Fabio Cardoso Cruz
- Departamento de Farmacologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Lucas de Oliveira Alvares
- Laboratório de Neurobiologia da Memória, Departamento de Biofísica, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
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7
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Leake J, Cardona LS, Mencevski F, Westbrook RF, Holmes NM. Context and Time Regulate Fear Memory Consolidation and Reconsolidation in the Basolateral Amygdala Complex. J Neurosci 2024; 44:e1698232023. [PMID: 38286626 PMCID: PMC10904089 DOI: 10.1523/jneurosci.1698-23.2023] [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: 09/10/2023] [Revised: 10/31/2023] [Accepted: 11/08/2023] [Indexed: 01/31/2024] Open
Abstract
It is widely accepted that fear memories are consolidated through protein synthesis-dependent changes in the basolateral amygdala complex (BLA). However, recent studies show that protein synthesis is not required to consolidate the memory of a new dangerous experience when it is similar to a prior experience. Here, we examined whether the protein synthesis requirement for consolidating the new experience varies with its spatial and temporal distance from the prior experience. Female and male rats were conditioned to fear a stimulus (S1, e.g., light) paired with shock in stage 1 and a second stimulus (S2, e.g., tone) that preceded additional S1-shock pairings (S2-S1-shock) in stage 2. The latter stage was followed by a BLA infusion of a protein synthesis inhibitor, cycloheximide, or vehicle. Subsequent testing with S2 revealed that protein synthesis in the BLA was not required to consolidate fear to S2 when the training stages occurred 48 h apart in the same context; was required when they were separated by 14 d or occurred in different contexts; but was again not required if S1 was re-presented after the delay or in the different context. Similarly, protein synthesis in the BLA was not required to reconsolidate fear to S2 when the training stages occurred 48 h apart but was required when they occurred 14 d apart. Thus, the protein synthesis requirement for consolidating/reconsolidating fear memories in the BLA is determined by similarity between present and past experiences, the time and place in which they occur, and reminders of the past experiences.
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Affiliation(s)
- Jessica Leake
- School of Psychology, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Luisa Saavedra Cardona
- School of Psychology, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Filip Mencevski
- School of Psychology, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - R Frederick Westbrook
- School of Psychology, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Nathan M Holmes
- School of Psychology, University of New South Wales, Sydney, New South Wales 2052, Australia
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8
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Jung JH, Wang Y, Rashid AJ, Zhang T, Frankland PW, Josselyn SA. Examining memory linking and generalization using scFLARE2, a temporally precise neuronal activity tagging system. Cell Rep 2023; 42:113592. [PMID: 38103203 PMCID: PMC10842737 DOI: 10.1016/j.celrep.2023.113592] [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: 08/28/2023] [Revised: 10/26/2023] [Accepted: 11/30/2023] [Indexed: 12/18/2023] Open
Abstract
How memories are organized in the brain influences whether they are remembered discretely versus linked with other experiences or whether generalized information is applied to entirely novel situations. Here, we used scFLARE2 (single-chain fast light- and activity-regulated expression 2), a temporally precise tagging system, to manipulate mouse lateral amygdala neurons active during one of two 3 min threat experiences occurring close (3 h) or further apart (27 h) in time. Silencing scFLARE2-tagged neurons showed that two threat experiences occurring at distal times are dis-allocated to orthogonal engram ensembles and remembered discretely, whereas the same two threat experiences occurring in close temporal proximity are linked via co-allocation to overlapping engram ensembles. Moreover, we found that co-allocation mediates memory generalization applied to a completely novel stimulus. These results indicate that endogenous temporal evolution of engram ensemble neuronal excitability determines how memories are organized and remembered and that this would not be possible using conventional immediate-early gene-based tagging methods.
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Affiliation(s)
- Jung Hoon Jung
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada
| | - Ying Wang
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Asim J Rashid
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada
| | - Tao Zhang
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada
| | - Paul W Frankland
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Psychology, University of Toronto, Toronto, ON M5S 3G3, Canada; Child & Brain Development Program, Canadian Institute for Advanced Research (CIFAR), Toronto, ON M5G 1M1, Canada
| | - Sheena A Josselyn
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Psychology, University of Toronto, Toronto, ON M5S 3G3, Canada.
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9
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Brosens N, Lesuis SL, Rao-Ruiz P, van den Oever MC, Krugers HJ. Shaping Memories Via Stress: A Synaptic Engram Perspective. Biol Psychiatry 2023:S0006-3223(23)01720-1. [PMID: 37977215 DOI: 10.1016/j.biopsych.2023.11.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 10/09/2023] [Accepted: 11/05/2023] [Indexed: 11/19/2023]
Abstract
Stress modulates the activity of various memory systems and can thereby guide behavioral interaction with the environment in an adaptive or maladaptive manner. At the cellular level, a large body of evidence indicates that (nor)adrenaline and glucocorticoid release induced by acute stress exposure affects synapse function and synaptic plasticity, which are critical substrates for learning and memory. Recent evidence suggests that memories are supported in the brain by sparsely distributed neurons within networks, termed engram cell ensembles. While the physiological and molecular effects of stress on the synapse are increasingly well characterized, how these synaptic modifications shape the multiscale dynamics of engram cell ensembles is still poorly understood. In this review, we discuss and integrate recent information on how acute stress affects synapse function and how this may alter engram cell ensembles and their synaptic connectivity to shape memory strength and memory precision. We provide a mechanistic framework of a synaptic engram under stress and put forward outstanding questions that address knowledge gaps in our understanding of the mechanisms that underlie stress-induced memory modulation.
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Affiliation(s)
- Niek Brosens
- Brain Plasticity Group, Swammerdam Institute for Life Sciences-Center for Neuroscience, University of Amsterdam, Amsterdam, the Netherlands.
| | - Sylvie L Lesuis
- Brain Plasticity Group, Swammerdam Institute for Life Sciences-Center for Neuroscience, University of Amsterdam, Amsterdam, the Netherlands; Cellular and Cognitive Neuroscience group, Swammerdam Institute for Life Sciences-Center for Neuroscience, University of Amsterdam, Amsterdam, the Netherlands
| | - Priyanka Rao-Ruiz
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Michel C van den Oever
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Harm J Krugers
- Brain Plasticity Group, Swammerdam Institute for Life Sciences-Center for Neuroscience, University of Amsterdam, Amsterdam, the Netherlands.
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Tse D, Privitera L, Norton AC, Gobbo F, Spooner P, Takeuchi T, Martin SJ, Morris RGM. Cell-type-specific optogenetic stimulation of the locus coeruleus induces slow-onset potentiation and enhances everyday memory in rats. Proc Natl Acad Sci U S A 2023; 120:e2307275120. [PMID: 37931094 PMCID: PMC10655220 DOI: 10.1073/pnas.2307275120] [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: 05/01/2023] [Accepted: 09/12/2023] [Indexed: 11/08/2023] Open
Abstract
Memory formation is typically divided into phases associated with encoding, storage, consolidation, and retrieval. The neural determinants of these phases are thought to differ. This study first investigated the impact of the experience of novelty in rats incurred at a different time, before or after, the precise moment of memory encoding. Memory retention was enhanced. Optogenetic activation of the locus coeruleus mimicked this enhancement induced by novelty, both when given before and after the moment of encoding. Optogenetic activation of the locus coeruleus also induced a slow-onset potentiation of field potentials in area CA1 of the hippocampus evoked by CA3 stimulation. Despite the locus coeruleus being considered a primarily noradrenergic area, both effects of such stimulation were blocked by the dopamine D1/D5 receptor antagonist SCH 23390. These findings substantiate and enrich the evidence implicating the locus coeruleus in cellular aspects of memory consolidation in hippocampus.
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Affiliation(s)
- Dorothy Tse
- Centre for Discovery Brain Sciences, Edinburgh Neuroscience, University of Edinburgh, EdinburghEH8 9JZ, United Kingdom
- Department of Psychology, Edge Hill University, OmskirkL39 4QP, United Kingdom
| | - Lucia Privitera
- Centre for Discovery Brain Sciences, Edinburgh Neuroscience, University of Edinburgh, EdinburghEH8 9JZ, United Kingdom
- School of Systems Medicine, University of Dundee, DundeeDD1 4HN, United Kingdom
- Barts and the London School of Medicine, Institute of Health Sciences Education, Queen Mary University of London Malta Campus, VictoriaVCT 2570, Malta
| | - Anna C. Norton
- Centre for Discovery Brain Sciences, Edinburgh Neuroscience, University of Edinburgh, EdinburghEH8 9JZ, United Kingdom
| | - Francesco Gobbo
- Centre for Discovery Brain Sciences, Edinburgh Neuroscience, University of Edinburgh, EdinburghEH8 9JZ, United Kingdom
| | - Patrick Spooner
- Centre for Discovery Brain Sciences, Edinburgh Neuroscience, University of Edinburgh, EdinburghEH8 9JZ, United Kingdom
| | - Tomonori Takeuchi
- Danish Research Institute of Translational Neuroscience, Nordic-European Molecular Biology Laboratory Partnership for Molecular Medicine, Aarhus University, Aarhus8000, Denmark
- Center for Proteins in Memory, Danish National Research Foundation, Department of Biomedicine, Aarhus University, Aarhus8000, Denmark
| | - Stephen J. Martin
- School of Systems Medicine, University of Dundee, DundeeDD1 4HN, United Kingdom
| | - Richard G. M. Morris
- Centre for Discovery Brain Sciences, Edinburgh Neuroscience, University of Edinburgh, EdinburghEH8 9JZ, United Kingdom
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11
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Antonoudiou P, Stone B, Colmers PLW, Evans-Strong A, Walton N, Weiss G, Maguire J. Experience-dependent information routing through the basolateral amygdala. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.02.551710. [PMID: 37577684 PMCID: PMC10418260 DOI: 10.1101/2023.08.02.551710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
The basolateral amygdala (BLA) is an emotional processing hub and is well-established to influence both positive and negative valence processing. Selective engagement of a heterogeneous cell population in the BLA is thought to contribute to this flexibility in valence processing. However, how this process is impacted by previous experiences which influence valence processing is unknown. Here we demonstrate that previous positive (EE) or negative (chronic unpredictable stress) experiences differentially influence the activity of specific populations of BLA principal neurons projecting to either the nucleus accumbens core or bed nucleus of the stria terminalis. Using chemogenetic manipulation of these projection-specific neurons we can mimic or occlude the effects of chronic unpredictable stress or enriched environment on valence processing to bidirectionally control avoidance behaviors and stress-induced helplessness. These data demonstrate that previous experiences influence the responsiveness of projection-specific BLA principal neurons, biasing information routing through the BLA, to govern valence processing.
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12
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El Matine R, Kreutzmann JC, Fendt M. Chronic unilateral inhibition of GABA synthesis in the amygdala increases specificity of conditioned fear in a discriminative fear conditioning paradigm in rats. Prog Neuropsychopharmacol Biol Psychiatry 2023; 124:110732. [PMID: 36792003 DOI: 10.1016/j.pnpbp.2023.110732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 01/31/2023] [Accepted: 02/10/2023] [Indexed: 02/16/2023]
Abstract
Neural activity in the amygdala is critical for fear learning. In anxiety disorder patients, bilateral hyperactivity of the amygdala can be observed. This hyperactivation is often associated with the facilitation of fear learning and/or over-generalization of conditioned fear. In contrast, hypoactivity of the amygdala, e.g. by pharmacological interventions, attenuates or blocks fear learning. To date, little is known about how neural excitability of the amygdala affects specificity or generalization of fear. Therefore, the present study utilized chronic inhibition of GABA synthesis in the amygdala to increase excitability and investigated the effect on the specificity of fear learning. In rats, unilateral cannulas aiming at the amygdala were implanted. The cannulas were connected to subcutaneously implanted osmotic mini pumps that delivered either the GABA synthesis inhibitor L-allylglycine or its inactive enantiomer D-allylglycine. Following one week of chronic GABA synthesis manipulation, the rats were submitted to a discriminative fear conditioning protocol. In addition, anxiety-like behavior in the light-dark box was measured. Our data show that chronic unilateral L-AG infusions into the amygdala improve the specificity of learned fear, support safety learning, and reduce fear generalization and anxiety. This data demonstrates that moderately increased amygdala excitability can be beneficial for the specificity of fear learning and highlights the potential application for therapeutic interventions.
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Affiliation(s)
- Rami El Matine
- Institute for Pharmacology and Toxicology, Otto-von-Guericke University, Magdeburg, Germany
| | - Judith C Kreutzmann
- Institute for Pharmacology and Toxicology, Otto-von-Guericke University, Magdeburg, Germany
| | - Markus Fendt
- Institute for Pharmacology and Toxicology, Otto-von-Guericke University, Magdeburg, Germany; Center for Behavioral Brain Sciences, Otto-von-Guericke University, Magdeburg, Germany.
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13
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Jung JH, Wang Y, Mocle AJ, Zhang T, Köhler S, Frankland PW, Josselyn SA. Examining the engram encoding specificity hypothesis in mice. Neuron 2023; 111:1830-1845.e5. [PMID: 36990091 DOI: 10.1016/j.neuron.2023.03.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 02/07/2023] [Accepted: 03/06/2023] [Indexed: 03/30/2023]
Abstract
According to the encoding specificity hypothesis, memory is best recalled by retrieval cues that overlap with training cues. Human studies generally support this hypothesis. However, memories are thought to be stored in neuronal ensembles (engrams), and retrieval cues are thought to reactivate neurons in an engram to induce memory recall. Here, we visualized engrams in mice to test whether retrieval cues that overlap with training cues produce maximal memory recall via high engram reactivation (engram encoding specificity hypothesis). Using variations of cued threat conditioning (pairing conditioned stimulus [CS] with footshock), we manipulated encoding and retrieval conditions along multiple domains, including pharmacological state, external sensory cue, and internal optogenetic cue. Maximal engram reactivation and memory recall occurred when retrieval conditions closely matched training conditions. These findings provide a biological basis for the encoding specificity hypothesis and highlight the important interaction between stored information (engram) and cues available at memory retrieval (ecphory).
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Affiliation(s)
- Jung Hoon Jung
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada
| | - Ying Wang
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Andrew J Mocle
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Tao Zhang
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada
| | - Stefan Köhler
- Department of Psychology, University of Western Ontario, London, ON N6A 5C2, Canada; The Brain and Mind Institute, University of Western Ontario, London, ON N6A 3K7, Canada
| | - Paul W Frankland
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Psychology, University of Toronto, Toronto, ON M5S 3G3, Canada; Child & Brain Development Program, Canadian Institute for Advanced Research (CIFAR), Toronto, ON M5G 1M1, Canada
| | - Sheena A Josselyn
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Psychology, University of Toronto, Toronto, ON M5S 3G3, Canada.
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14
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Abstract
Research in the last century has provided insight into the systems, cellular, and molecular processes involved in the formation, storage, recall, and update of memory engrams - the physical manifestation of the long sought-after philosophical and psychological concept of memory traces. Recent technologies allow scientists to visualize the key molecular players involved in segregating, ordering, and linking memories close in time, for future treatment of "disorders of the engram" where memory linking is deficient (e.g., cognitive aging or Alzheimer's) or excessive (e.g., PTSD).
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Affiliation(s)
- Catalin V Buhusi
- Department of Psychology, Interdisciplinary Program in Neuroscience, USTAR BioInnovations Center, Utah State University, Logan, UT, 84322, USA.
| | - Mona Buhusi
- Department of Psychology, Interdisciplinary Program in Neuroscience, USTAR BioInnovations Center, Utah State University, Logan, UT, 84322, USA
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15
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Park A, Jacob AD, Hsiang HLL, Frankland PW, Howland JG, Josselyn SA. Formation and fate of an engram in the lateral amygdala supporting a rewarding memory in mice. Neuropsychopharmacology 2023; 48:724-733. [PMID: 36261624 PMCID: PMC10066178 DOI: 10.1038/s41386-022-01472-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 09/27/2022] [Accepted: 10/01/2022] [Indexed: 11/08/2022]
Abstract
Memories allow past experiences to guide future decision making and behavior. Sparse ensembles of neurons, known as engrams, are thought to store memories in the brain. Most previous research has focused on engrams supporting threatening or fearful memories where results show that neurons involved in a particular engram ("engram neurons") are both necessary and sufficient for memory expression. Far less is understood about engrams supporting appetitive or rewarding memories. As circumstances and environments are dynamic, the fate of a previously acquired engram with changing circumstances is unknown. Here we examined how engrams supporting a rewarding cue-cocaine memory are formed and whether this original engram is important in reinstatement of memory-guided behavior following extinction. Using a variety of techniques, we show that neurons in the lateral amygdala are allocated to an engram based on relative neuronal excitability at training. Furthermore, once allocated, these neurons become both necessary and sufficient for behavior consistent with recall of that rewarding memory. Allocated neurons are also critical for cocaine-primed reinstatement of memory-guided behavior following extinction. Moreover, artificial reactivation of initially allocated neurons supports reinstatement-like behavior following extinction even in the absence of cocaine-priming. Together, these findings suggest that cocaine priming after extinction reactivates the original engram, and that memory-guided reinstatement behavior does not occur in the absence of this reactivation. Although we focused on neurons in one brain region only, our findings that manipulations of lateral amygdala engram neurons alone were sufficient to impact memory-guided behavior indicate that the lateral amygdala is a critical hub region in what may be a larger brain-wide engram.
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Affiliation(s)
- Albert Park
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Ave., Toronto, ON, M5G 1X8, Canada
| | - Alexander D Jacob
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Ave., Toronto, ON, M5G 1X8, Canada
- Department of Psychology, University of Toronto, Toronto, ON, M5G 1X8, Canada
| | - Hwa-Lin Liz Hsiang
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Ave., Toronto, ON, M5G 1X8, Canada
| | - Paul W Frankland
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Ave., Toronto, ON, M5G 1X8, Canada
- Department of Psychology, University of Toronto, Toronto, ON, M5G 1X8, Canada
- Department of Physiology, University of Toronto, Toronto, ON, M5G 1X8, Canada
- Child & Brain Development Program, Canadian Institute for Advanced Research (CIFAR), Toronto, ON, M5G 1M1, Canada
| | - John G Howland
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, SK, S7N 5E5, Canada.
| | - Sheena A Josselyn
- Program in Neurosciences & Mental Health, Hospital for Sick Children, 555 University Ave., Toronto, ON, M5G 1X8, Canada.
- Department of Psychology, University of Toronto, Toronto, ON, M5G 1X8, Canada.
- Department of Physiology, University of Toronto, Toronto, ON, M5G 1X8, Canada.
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16
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The times they are a-changin': a proposal on how brain flexibility goes beyond the obvious to include the concepts of "upward" and "downward" to neuroplasticity. Mol Psychiatry 2023; 28:977-992. [PMID: 36575306 PMCID: PMC10005965 DOI: 10.1038/s41380-022-01931-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 12/07/2022] [Accepted: 12/14/2022] [Indexed: 12/28/2022]
Abstract
Since the brain was found to be somehow flexible, plastic, researchers worldwide have been trying to comprehend its fundamentals to better understand the brain itself, make predictions, disentangle the neurobiology of brain diseases, and finally propose up-to-date treatments. Neuroplasticity is simple as a concept, but extremely complex when it comes to its mechanisms. This review aims to bring to light an aspect about neuroplasticity that is often not given enough attention as it should, the fact that the brain's ability to change would include its ability to disconnect synapses. So, neuronal shrinkage, decrease in spine density or dendritic complexity should be included within the concept of neuroplasticity as part of its mechanisms, not as an impairment of it. To that end, we extensively describe a variety of studies involving topics such as neurodevelopment, aging, stress, memory and homeostatic plasticity to highlight how the weakening and disconnection of synapses organically permeate the brain in so many ways as a good practice of its intrinsic physiology. Therefore, we propose to break down neuroplasticity into two sub-concepts, "upward neuroplasticity" for changes related to synaptic construction and "downward neuroplasticity" for changes related to synaptic deconstruction. With these sub-concepts, neuroplasticity could be better understood from a bigger landscape as a vector in which both directions could be taken for the brain to flexibly adapt to certain demands. Such a paradigm shift would allow a better understanding of the concept of neuroplasticity to avoid any data interpretation bias, once it makes clear that there is no morality with regard to the organic and physiological changes that involve dynamic biological systems as seen in the brain.
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Buhusi CV, Oprisan SA, Buhusi M. The future of integrative neuroscience: The big questions. Front Integr Neurosci 2023; 17:1113238. [PMID: 36908505 PMCID: PMC9995763 DOI: 10.3389/fnint.2023.1113238] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 01/27/2023] [Indexed: 02/25/2023] Open
Affiliation(s)
- Catalin V Buhusi
- Interdisciplinary Program in Neuroscience, Department of Psychology, USTAR BioInnovations Center, Utah State University, Logan, UT, United States
| | - Sorinel A Oprisan
- Department of Physics and Astronomy, College of Charleston, Charleston, SC, United States
| | - Mona Buhusi
- Interdisciplinary Program in Neuroscience, Department of Psychology, USTAR BioInnovations Center, Utah State University, Logan, UT, United States
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18
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Park S, Jung JH, Karimi SA, Jacob AD, Josselyn SA. Opto-extinction of a threat memory in mice. Brain Res Bull 2022; 191:61-68. [DOI: 10.1016/j.brainresbull.2022.10.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 10/17/2022] [Indexed: 11/02/2022]
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19
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Sung Y, Kaang BK. The Three Musketeers in the Medial Prefrontal Cortex: Subregion-specific Structural and Functional Plasticity Underlying Fear Memory Stages. Exp Neurobiol 2022; 31:221-231. [PMID: 36050222 PMCID: PMC9471411 DOI: 10.5607/en22012] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Revised: 06/23/2022] [Accepted: 07/04/2022] [Indexed: 11/23/2022] Open
Abstract
Fear memory recruits various brain regions with long-lasting brain-wide subcellular events. The medial prefrontal cortex processes the emotional and cognitive functions required for adequately handling fear memory. Several studies have indicated that subdivisions within the medial prefrontal cortex, namely the prelimbic, infralimbic, and anterior cingulate cortices, may play different roles across fear memory states. Through a dedicated cytoarchitecture and connectivity, the three different regions of the medial prefrontal cortex play a specific role in maintaining and extinguishing fear memory. Furthermore, synaptic plasticity and maturation of neural circuits within the medial prefrontal cortex suggest that remote memories undergo structural and functional reorganization. Finally, recent technical advances have enabled genetic access to transiently activated neuronal ensembles within these regions, suggesting that memory trace cells in these regions may preferentially contribute to processing specific fear memory. We reviewed recently published reports and summarize the molecular, synaptic and cellular events occurring within the medial prefrontal cortex during various memory stages.
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Affiliation(s)
- Yongmin Sung
- School of Biological Sciences, Seoul National University, Seoul 08826, Korea
| | - Bong-Kiun Kaang
- School of Biological Sciences, Seoul National University, Seoul 08826, Korea
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20
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Formation of False Context Fear Memory Is Regulated by Hypothalamic Corticotropin-Releasing Factor in Mice. Int J Mol Sci 2022; 23:ijms23116286. [PMID: 35682965 PMCID: PMC9181353 DOI: 10.3390/ijms23116286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 05/29/2022] [Accepted: 05/30/2022] [Indexed: 12/10/2022] Open
Abstract
Traumatic events frequently produce false fear memories. We investigated the effect of hypothalamic corticotropin-releasing factor (CRF) knockdown (Hy-Crf-KD) or overexpression (Hy-CRF-OE) on contextual fear memory, as fear stress-released CRF and hypothalamic-pituitary-adrenal axis activation affects the memory system. Mice were placed in a chamber with an electric footshock as a conditioning stimulus (CS) in Context A, then exposed to a novel chamber without CS, as Context B, at 3 h (B-3h) or 24 h (B-24h). The freezing response in B-3h was intensified in the experimental mice, compared to control mice not exposed to CS, indicating that a false fear memory was formed at 3 h. The within-group freezing level at B-24h was higher than that at B-3h, indicating that false context fear memory was enhanced at B-24h. The difference in freezing levels between B-3h and B-24h in Hy-Crf-KD mice was larger than that of controls. In Hy-CRF-OE mice, the freezing level at B-3h was higher than that of control and Hy-Crf-KD mice, while the freezing level in B-24h was similar to that in B-3h. Locomotor activity before CS and freezing level during CS were similar among the groups. Therefore, we hypothesized that Hy-Crf-KD potentiates the induction of false context fear memory, while Hy-CRF-OE enhances the onset of false fear memory formation.
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21
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Shridhar S, Mishra P, Narayanan R. Dominant role of adult neurogenesis-induced structural heterogeneities in driving plasticity heterogeneity in dentate gyrus granule cells. Hippocampus 2022; 32:488-516. [PMID: 35561083 PMCID: PMC9322436 DOI: 10.1002/hipo.23422] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 04/21/2022] [Accepted: 04/28/2022] [Indexed: 02/02/2023]
Abstract
Neurons and synapses manifest pronounced variability in the amount of plasticity induced by identical activity patterns. The mechanisms underlying such plasticity heterogeneity, which have been implicated in context‐specific resource allocation during encoding, have remained unexplored. Here, we employed a systematic physiologically constrained parametric search to identify the cellular mechanisms behind plasticity heterogeneity in dentate gyrus granule cells. We used heterogeneous model populations to ensure that our conclusions were not biased by parametric choices in a single hand‐tuned model. We found that each of intrinsic, synaptic, and structural heterogeneities independently yielded heterogeneities in synaptic plasticity profiles obtained with two different induction protocols. However, among the disparate forms of neural‐circuit heterogeneities, our analyses demonstrated the dominance of neurogenesis‐induced structural heterogeneities in driving plasticity heterogeneity in granule cells. We found that strong relationships between neuronal intrinsic excitability and plasticity emerged only when adult neurogenesis‐induced heterogeneities in neural structure were accounted for. Importantly, our analyses showed that it was not imperative that the manifestation of neural‐circuit heterogeneities must translate to heterogeneities in plasticity profiles. Specifically, despite the expression of heterogeneities in structural, synaptic, and intrinsic neuronal properties, similar plasticity profiles were attainable across all models through synergistic interactions among these heterogeneities. We assessed the parametric combinations required for the manifestation of such degeneracy in the expression of plasticity profiles. We found that immature cells showed physiological plasticity profiles despite receiving afferent inputs with weak synaptic strengths. Thus, the high intrinsic excitability of immature granule cells was sufficient to counterbalance their low excitatory drive in the expression of plasticity profile degeneracy. Together, our analyses demonstrate that disparate forms of neural‐circuit heterogeneities could mechanistically drive plasticity heterogeneity, but also caution against treating neural‐circuit heterogeneities as proxies for plasticity heterogeneity. Our study emphasizes the need for quantitatively characterizing the relationship between neural‐circuit and plasticity heterogeneities across brain regions.
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Affiliation(s)
- Sameera Shridhar
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, India
| | - Poonam Mishra
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, India
| | - Rishikesh Narayanan
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, India
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22
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Abstract
In an analysis of memory systems, Sherry and Schacter (Psychological Review, 94, 439-454, 1987) emphasized the importance of functional and evolutionary considerations for characterizing mechanisms of memory. The present article considers four different yet closely related topics from more recent research in which similar considerations have played a prominent role in shaping both experiment and theory: the seven sins of memory, mechanisms underlying memory misattribution errors, the role of memory in imagining future experiences, and the relation between associative inference and memory errors. These lines of research illustrate the usefulness of attempting to integrate functional and mechanistic considerations, in line with the general approach articulated by Sherry and Schacter.
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23
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Mishra P, Narayanan R. Stable continual learning through structured multiscale plasticity manifolds. Curr Opin Neurobiol 2021; 70:51-63. [PMID: 34416674 PMCID: PMC7611638 DOI: 10.1016/j.conb.2021.07.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Revised: 07/15/2021] [Accepted: 07/19/2021] [Indexed: 11/16/2022]
Abstract
Biological plasticity is ubiquitous. How does the brain navigate this complex plasticity space, where any component can seemingly change, in adapting to an ever-changing environment? We build a systematic case that stable continuous learning is achieved by structured rules that enforce multiple, but not all, components to change together in specific directions. This rule-based low-dimensional plasticity manifold of permitted plasticity combinations emerges from cell type-specific molecular signaling and triggers cascading impacts that span multiple scales. These multiscale plasticity manifolds form the basis for behavioral learning and are dynamic entities that are altered by neuromodulation, metaplasticity, and pathology. We explore the strong links between heterogeneities, degeneracy, and plasticity manifolds and emphasize the need to incorporate plasticity manifolds into learning-theoretical frameworks and experimental designs.
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Affiliation(s)
- Poonam Mishra
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
| | - Rishikesh Narayanan
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
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Fuentes-Ramos M, Alaiz-Noya M, Barco A. Transcriptome and epigenome analysis of engram cells: Next-generation sequencing technologies in memory research. Neurosci Biobehav Rev 2021; 127:865-875. [PMID: 34097980 DOI: 10.1016/j.neubiorev.2021.06.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 06/02/2021] [Accepted: 06/03/2021] [Indexed: 12/19/2022]
Abstract
Transcription and epigenetic changes are integral components of the neuronal response to stimulation and have been postulated to be drivers or substrates for enduring changes in animal behavior, including learning and memory. Memories are thought to be deposited in neuronal assemblies called engrams, i.e., groups of cells that undergo persistent physical or chemical changes during learning and are selectively reactivated to retrieve the memory. Despite the research progress made in recent years, the identity of specific epigenetic changes, if any, that occur in these cells and subsequently contribute to the persistence of memory traces remains unknown. The analysis of these changes is challenging due to the difficulty of exploring molecular alterations that only occur in a relatively small percentage of cells embedded in a complex tissue. In this review, we discuss the recent advances in this field and the promise of next-generation sequencing (NGS) and epigenome editing methods for overcoming these challenges and address long-standing questions concerning the role of epigenetic mechanisms in memory encoding, maintenance and expression.
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Affiliation(s)
- Miguel Fuentes-Ramos
- Instituto de Neurociencias, Universidad Miguel Hernández - Consejo Superior de Investigaciones Científicas, Av. Santiago Ramón y Cajal s/n, Sant Joan d'Alacant, 03550, Alicante, Spain
| | - Marta Alaiz-Noya
- Instituto de Neurociencias, Universidad Miguel Hernández - Consejo Superior de Investigaciones Científicas, Av. Santiago Ramón y Cajal s/n, Sant Joan d'Alacant, 03550, Alicante, Spain
| | - Angel Barco
- Instituto de Neurociencias, Universidad Miguel Hernández - Consejo Superior de Investigaciones Científicas, Av. Santiago Ramón y Cajal s/n, Sant Joan d'Alacant, 03550, Alicante, Spain.
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