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https://www.readbyqxmd.com/read/29903974/reactivation-of-recall-induced-neurons-contributes-to-remote-fear-memory-attenuation
#1
Ossama Khalaf, Siegfried Resch, Lucie Dixsaut, Victoire Gorden, Liliane Glauser, Johannes Gräff
Whether fear attenuation is mediated by inhibition of the original memory trace of fear with a new memory trace of safety or by updating of the original fear trace toward safety has been a long-standing question in neuroscience and psychology alike. In particular, which of the two scenarios underlies the attenuation of remote (month-old) fear memories is completely unknown, despite the impetus to better understand this process against the backdrop of enduring traumata. We found-chemogenetically and in an engram-specific manner-that effective remote fear attenuation is accompanied by the reactivation of memory recall-induced neurons in the dentate gyrus and that the continued activity of these neurons is critical for fear reduction...
June 15, 2018: Science
https://www.readbyqxmd.com/read/29903972/synapse-specific-representation-of-the-identity-of-overlapping-memory-engrams
#2
Kareem Abdou, Mohammad Shehata, Kiriko Choko, Hirofumi Nishizono, Mina Matsuo, Shin-Ichi Muramatsu, Kaoru Inokuchi
Memories are integrated into interconnected networks; nevertheless, each memory has its own identity. How the brain defines specific memory identity out of intermingled memories stored in a shared cell ensemble has remained elusive. We found that after complete retrograde amnesia of auditory fear conditioning in mice, optogenetic stimulation of the auditory inputs to the lateral amygdala failed to induce memory recall, implying that the memory engram no longer existed in that circuit. Complete amnesia of a given fear memory did not affect another linked fear memory encoded in the shared ensemble...
June 15, 2018: Science
https://www.readbyqxmd.com/read/29888747/synaptic-potential-and-plasticity-of-an-sk2-channel-gate-regulate-spike-burst-activity-in-cerebellar-purkinje-cells
#3
Gen Ohtsuki, Christian Hansel
Neurons store information and participate in memory engrams as a result of experience-dependent changes in synaptic weights and in membrane excitability. Here, we examine excitatory postsynaptic potential (EPSP) amplitude and neuronal excitability in relation to these two mechanisms of plasticity. We analyze somato-dendritic double-patch recordings from cerebellar Purkinje cells while inducing intrinsic, SK2 channel-dependent plasticity or blocking SK channels with bath application of apamin. Both manipulations increase the build-up of EPSP amplitudes during an EPSP train and enhance the number of EPSP-evoked spikes, yielding insights into the mechanistic contribution of EPSP amplitude to single spikes and spike bursts...
March 23, 2018: iScience
https://www.readbyqxmd.com/read/29887312/spatial-memory-engram-in-the-mouse-retrosplenial-cortex
#4
Michal M Milczarek, Seralynne D Vann, Frank Sengpiel
Memory relies on lasting adaptations of neuronal properties elicited by stimulus-driven plastic changes [1]. The strengthening (and weakening) of synapses results in the establishment of functional ensembles. It is presumed that such ensembles (or engrams) are activated during memory acquisition and re-activated upon memory retrieval. The retrosplenial cortex (RSC) has emerged as a key brain area supporting memory [2], including episodic and topographical memory in humans [3-5], as well as spatial memory in rodents [6, 7]...
May 30, 2018: Current Biology: CB
https://www.readbyqxmd.com/read/29875406/parallel-emergence-of-stable-and-dynamic-memory-engrams-in-the-hippocampus
#5
Thomas Hainmueller, Marlene Bartos
During our daily life, we depend on memories of past experiences to plan future behaviour. These memories are represented by the activity of specific neuronal groups or 'engrams'1,2 . Neuronal engrams are assembled during learning by synaptic modification, and engram reactivation represents the memorized experience 1 . Engrams of conscious memories are initially stored in the hippocampus for several days and then transferred to cortical areas 2 . In the dentate gyrus of the hippocampus, granule cells transform rich inputs from the entorhinal cortex into a sparse output, which is forwarded to the highly interconnected pyramidal cell network in hippocampal area CA3 3 ...
June 6, 2018: Nature
https://www.readbyqxmd.com/read/29849443/garth-j-thomas-physiological-psychologist-an-appraisal-of-his-contributions-to-memory-research
#6
REVIEW
Anny Tzouma, Lazaros C Triarhou
This note is a tribute to Garth J. Thomas (1916-2008), late Professor of Brain Research at the University of Rochester, New York. Thomas was an influential psychologist, albeit for his research in learning and memory, as much as for his work as editor of the Journal of Comparative and Physiological Psychology . In his studies, he combined experimental lesions with behavioral analyses. He introduced the terms "dispositional" and "representational" to describe the 2 different types of memory function, and emphasized that memory must be studied not only through behavioristic psychology, but also in a molecular and physiological context...
May 2018: Annals of Neurosciences
https://www.readbyqxmd.com/read/29845977/an-emerging-role-for-rna-in-a-memory-like-behavioral-effect-in-aplysia
#7
COMMENT
Rosalind Se Carney
Highlighted Research Paper: RNA from Trained Aplysia Can Induce an Epigenetic Engram for Long-Term Sensitization in Untrained Aplysia , by Alexis Bédécarrats, Shanping Chen, Kaycey Pearce, Diancai Cai and David L. Glanzman.
May 2018: ENeuro
https://www.readbyqxmd.com/read/29789810/rna-from-trained-aplysia-can-induce-an-epigenetic-engram-for-long-term-sensitization-in-untrained-aplysia
#8
Alexis Bédécarrats, Shanping Chen, Kaycey Pearce, Diancai Cai, David L Glanzman
The precise nature of the engram, the physical substrate of memory, remains uncertain. Here, it is reported that RNA extracted from the central nervous system of Aplysia given long-term sensitization (LTS) training induced sensitization when injected into untrained animals; furthermore, the RNA-induced sensitization, like training-induced sensitization, required DNA methylation. In cellular experiments, treatment with RNA extracted from trained animals was found to increase excitability in sensory neurons, but not in motor neurons, dissociated from naïve animals...
May 2018: ENeuro
https://www.readbyqxmd.com/read/29784659/united-states-of-amnesia-rescuing-memory-loss-from-diverse-conditions
#9
EDITORIAL
Clara Ortega-de San Luis, Tomás J Ryan
Amnesia - the loss of memory function - is often the earliest and most persistent symptom of dementia. It occurs as a consequence of a variety of diseases and injuries. These include neurodegenerative, neurological or immune disorders, drug abuse, stroke or head injuries. It has both troubled and fascinated humanity. Philosophers, scientists, physicians and anatomists have all pursued an understanding of how we learn and memorise, and why we forget. In the last few years, the development of memory engram labelling technology has greatly impacted how we can experimentally study memory and its disorders in animals...
May 18, 2018: Disease Models & Mechanisms
https://www.readbyqxmd.com/read/29709212/memory-allocation-mechanisms-and-function
#10
Sheena A Josselyn, Paul W Frankland
Memories for events are thought to be represented in sparse, distributed neuronal ensembles (or engrams). In this article, we review how neurons are chosen to become part of a particular engram, via a process of neuronal allocation. Experiments in rodents indicate that eligible neurons compete for allocation to a given engram, with more excitable neurons winning this competition. Moreover, fluctuations in neuronal excitability determine how engrams interact, promoting either memory integration (via coallocation to overlapping engrams) or separation (via disallocation to nonoverlapping engrams)...
April 25, 2018: Annual Review of Neuroscience
https://www.readbyqxmd.com/read/29700265/interregional-synaptic-maps-among-engram-cells-underlie-memory-formation
#11
Jun-Hyeok Choi, Su-Eon Sim, Ji-Il Kim, Dong Il Choi, Jihae Oh, Sanghyun Ye, Jaehyun Lee, TaeHyun Kim, Hyoung-Gon Ko, Chae-Seok Lim, Bong-Kiun Kaang
Memory resides in engram cells distributed across the brain. However, the site-specific substrate within these engram cells remains theoretical, even though it is generally accepted that synaptic plasticity encodes memories. We developed the dual-eGRASP (green fluorescent protein reconstitution across synaptic partners) technique to examine synapses between engram cells to identify the specific neuronal site for memory storage. We found an increased number and size of spines on CA1 engram cells receiving input from CA3 engram cells...
April 27, 2018: Science
https://www.readbyqxmd.com/read/29695960/memory-synapses-are-defined-by-distinct-molecular-complexes-a-proposal
#12
REVIEW
Wayne S Sossin
Synapses are diverse in form and function. While there are strong evidential and theoretical reasons for believing that memories are stored at synapses, the concept of a specialized "memory synapse" is rarely discussed. Here, we review the evidence that memories are stored at the synapse and consider the opposing possibilities. We argue that if memories are stored in an active fashion at synapses, then these memory synapses must have distinct molecular complexes that distinguish them from other synapses...
2018: Frontiers in Synaptic Neuroscience
https://www.readbyqxmd.com/read/29663578/optimization-of-immunolabeling-and-clearing-techniques-for-indelibly-labeled-memory-traces
#13
Ina P Pavlova, Shannon C Shipley, Marcos Lanio, René Hen, Christine A Denny
Recent genetic tools have allowed researchers to visualize and manipulate memory traces (i.e. engrams) in small brain regions. However, the ultimate goal is to visualize memory traces across the entire brain in order to better understand how memories are stored in neural networks and how multiple memories may coexist. Intact tissue clearing and imaging is a new and rapidly growing area of focus that could accomplish this task. Here, we utilized the leading protocols for whole-brain clearing and applied them to the ArcCreERT2 mice, a murine line that allows for the indelible labeling of memory traces...
April 16, 2018: Hippocampus
https://www.readbyqxmd.com/read/29615619/pharmacologically-induced-amnesia-for-learned-fear-is-time-and-sleep-dependent
#14
Merel Kindt, Marieke Soeter
The discovery in animal research that fear memories may change upon retrieval has sparked a wave of interest into whether this phenomenon of reconsolidation also occurs in humans. The critical conditions under which memory reconsolidation can be observed and targeted in humans, however, remain elusive. Here we report that blocking beta-adrenergic receptors in the brain, either before or after reactivation, effectively neutralizes the expression of fear memory. We show a specific time-window during which beta-adrenergic receptors are involved in the reconsolidation of fear memory...
April 3, 2018: Nature Communications
https://www.readbyqxmd.com/read/29578411/dendritic-spikes-in-hippocampal-granule-cells-are-necessary-for-long-term-potentiation-at-the-perforant-path-synapse
#15
Sooyun Kim, Yoonsub Kim, Suk-Ho Lee, Won-Kyung Ho
Long-term potentiation (LTP) of synaptic responses is essential for hippocampal memory function. Perforant-path (PP) synapses on hippocampal granule cells (GCs) contribute to the formation of associative memories, which are considered the cellular correlates of memory engrams. However, the mechanisms of LTP at these synapses are not well understood. Due to sparse firing activity and the voltage attenuation in their dendrites, it remains unclear how associative LTP at distal synapses occurs. Here, we show that NMDA receptor-dependent LTP can be induced at PP-GC synapses without backpropagating action potentials (bAPs) in acute rat brain slices...
March 26, 2018: ELife
https://www.readbyqxmd.com/read/29554926/interaction-of-basolateral-amygdala-ventral-hippocampus-and-medial-prefrontal-cortex-regulates-the-consolidation-and-extinction-of-social-fear
#16
Chu-Chu Qi, Qing-Jun Wang, Xue-Zhu Ma, Hai-Chao Chen, Li-Ping Gao, Jie Yin, Yu-Hong Jing
BACKGROUND: Following a social defeat, the balanced establishment and extinction of aversive information is a beneficial strategy for individual survival. Abnormal establishment or extinction is implicated in the development of mental disorders. This study investigated the time course of the establishment and extinction of aversive information from acute social defeat and the temporal responsiveness of the basolateral amygdala (BLA), ventral hippocampus (vHIP) and medial prefrontal cortex (mPFC) in this process...
March 19, 2018: Behavioral and Brain Functions: BBF
https://www.readbyqxmd.com/read/29529016/dentate-granule-cell-recruitment-of-feedforward-inhibition-governs-engram-maintenance-and-remote-memory-generalization
#17
Nannan Guo, Marta E Soden, Charlotte Herber, Michael TaeWoo Kim, Antoine Besnard, Paoyan Lin, Xiang Ma, Constance L Cepko, Larry S Zweifel, Amar Sahay
Memories become less precise and generalized over time as memory traces reorganize in hippocampal-cortical networks. Increased time-dependent loss of memory precision is characterized by an overgeneralization of fear in individuals with post-traumatic stress disorder (PTSD) or age-related cognitive impairments. In the hippocampal dentate gyrus (DG), memories are thought to be encoded by so-called 'engram-bearing' dentate granule cells (eDGCs). Here we show, using rodents, that contextual fear conditioning increases connectivity between eDGCs and inhibitory interneurons (INs) in the downstream hippocampal CA3 region...
May 2018: Nature Medicine
https://www.readbyqxmd.com/read/29357783/the-ever-changing-engram-towards-an-integrated-understanding-of-long-term-memory-dynamics
#18
Almut Hupbach
No abstract text is available yet for this article.
March 2018: Memory
https://www.readbyqxmd.com/read/29284750/cyclic-amp-dependent-plasticity-underlies-rapid-changes-in-odor-coding-associated-with-reward-learning
#19
Thierry Louis, Aaron Stahl, Tamara Boto, Seth M Tomchik
Learning and memory rely on dopamine and downstream cAMP-dependent plasticity across diverse organisms. Despite the central role of cAMP signaling, it is not known how cAMP-dependent plasticity drives coherent changes in neuronal physiology that encode the memory trace, or engram. In Drosophila , the mushroom body (MB) is critically involved in olfactory classical conditioning, and cAMP signaling molecules are necessary and sufficient for normal memory in intrinsic MB neurons. To evaluate the role of cAMP-dependent plasticity in learning, we examined how cAMP manipulations and olfactory classical conditioning modulate olfactory responses in the MB with in vivo imaging...
January 16, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29279411/removal-of-perineuronal-nets-disrupts-recall-of-a-remote-fear-memory
#20
Elise Holter Thompson, Kristian Kinden Lensjø, Mattis Brænne Wigestrand, Anders Malthe-Sørenssen, Torkel Hafting, Marianne Fyhn
Throughout life animals learn to recognize cues that signal danger and instantaneously initiate an adequate threat response. Memories of such associations may last a lifetime and far outlast the intracellular molecules currently found to be important for memory processing. The memory engram may be supported by other more stable molecular components, such as the extracellular matrix structure of perineuronal nets (PNNs). Here, we show that recall of remote, but not recent, visual fear memories in rats depend on intact PNNs in the secondary visual cortex (V2L)...
January 16, 2018: Proceedings of the National Academy of Sciences of the United States of America
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