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https://www.readbyqxmd.com/read/29663578/optimization-of-immunolabeling-and-clearing-techniques-for-indelibly-labeled-memory-traces
#1
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
#2
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
#3
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
#4
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
#5
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...
March 12, 2018: Nature Medicine
https://www.readbyqxmd.com/read/29357783/the-ever-changing-engram-towards-an-integrated-understanding-of-long-term-memory-dynamics
#6
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
#7
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
#8
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
https://www.readbyqxmd.com/read/29279390/locus-coeruleus-input-to-hippocampal-ca3-drives-single-trial-learning-of-a-novel-context
#9
Akiko Wagatsuma, Teruhiro Okuyama, Chen Sun, Lillian M Smith, Kuniya Abe, Susumu Tonegawa
The memory for a new episode is formed immediately upon experience and can last up to a lifetime. It has been shown that the hippocampal network plays a fundamental role in the rapid acquisition of a memory of a one-time experience, in which the novelty component of the experience promotes the prompt formation of the memory. However, it remains unclear which neural circuits convey the novelty signal to the hippocampus for the single-trial learning. Here, we show that during encoding neuromodulatory input from locus coeruleus (LC) to CA3, but not CA1 or to the dentate gyrus, is necessary to facilitate novel contextual learning...
January 9, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29209962/effects-of-location-and-extent-of-spine-clustering-on-synaptic-integration-in-striatal-medium-spiny-neurons-a-computational-study
#10
Mrunal Rane, Rohit Manchanda
The nucleus accumbens (NAc) is known widely for its role in the reward circuit, which is dysregulated in a number of psychological disorders. Recent evidence also suggests the contribution of this structure in spatial and gustatory memories. Because of its role in different types of memories, similar to the hippocampus, we assumed the formation of spine clusters, which are engrams of memory, to be present on dendrites of medium spiny neurons (MSNs). We found that the activation of clustered inputs resulted in sublinear summation when clusters were present on the same branch and also when inputs were distributed on different branches...
December 6, 2017: Medical & Biological Engineering & Computing
https://www.readbyqxmd.com/read/29187215/criteria-for-identifying-the-molecular-basis-of-the-engram-camkii-pkmzeta
#11
REVIEW
John Lisman
The engram refers to the molecular changes by which a memory is stored in the brain. Substantial evidence suggests that memory involves learning-dependent changes at synapses, a process termed long-term potentiation (LTP). Thus, understanding the storages process that underlies LTP may provide insight into how the engram is stored. LTP involves induction, maintenance (storage), and expression sub-processes; special tests are required to specifically reveal properties of the storage process. The strongest of these is the Erasure test in which a transiently applied agent that attacks a putative storage molecule may lead to persistent erasure of previously induced LTP/memory...
November 29, 2017: Molecular Brain
https://www.readbyqxmd.com/read/29136107/contextual-fear-extinction-induces-hippocampal-metaplasticity-mediated-by-metabotropic-glutamate-receptor-5
#12
Branden J Stansley, Nicole M Fisher, Rocco G Gogliotti, Craig W Lindsley, P Jeffrey Conn, Colleen M Niswender
Dysregulated fear memory can lead to a broad spectrum of anxiety disorders. The brain systems underlying fear memory are manifold, with the hippocampus being prominently involved by housing fear-related spatial memories as engrams, which are created and stored through neural changes such as synaptic plasticity. Although metabotropic glutamate (mGlu) receptors contribute significantly to both fear behavior and hippocampal synaptic plasticity, the relationship between these two phenomena has not been fully elucidated...
November 9, 2017: Cerebral Cortex
https://www.readbyqxmd.com/read/29078397/silent-memory-engrams-as-the-basis-for-retrograde-amnesia
#13
Dheeraj S Roy, Shruti Muralidhar, Lillian M Smith, Susumu Tonegawa
Recent studies identified neuronal ensembles and circuits that hold specific memory information (memory engrams). Memory engrams are retained under protein synthesis inhibition-induced retrograde amnesia. These engram cells can be activated by optogenetic stimulation for full-fledged recall, but not by stimulation using natural recall cues (thus, amnesia). We call this state of engrams "silent engrams" and the cells bearing them "silent engram cells." The retention of memory information under amnesia suggests that the time-limited protein synthesis following learning is dispensable for memory storage, but may be necessary for effective memory retrieval processes...
November 14, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28891529/nonsynaptic-plasticity-model-of-long-term-memory-engrams
#14
L A Cacha, J Ali, Z H Rizvi, P P Yupapin, R R Poznanski
Using steady-state electrical properties of non-ohmic dendrite based on cable theory, we derive electrotonic potentials that do not change over time and are localized in space. We hypothesize that clusters of such stationary, local and permanent pulses are the electrical signatures of enduring memories which are imprinted through nonsynaptic plasticity, encoded through epigenetic mechanisms, and decoded through electrotonic processing. We further hypothesize how retrieval of an engram is made possible by integration of these permanently imprinted standing pulses in a neural circuit through neurotransmission in the extracellular space as part of conscious recall that acts as a guiding template in the reconsolidation of long-term memories through novelty characterized by uncertainty that arises when new fragments of memories reinstate an engram by way of nonsynaptic plasticity that permits its destabilization...
2017: Journal of Integrative Neuroscience
https://www.readbyqxmd.com/read/28772119/the-biology-of-forgetting-a-perspective
#15
REVIEW
Ronald L Davis, Yi Zhong
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...
August 2, 2017: Neuron
https://www.readbyqxmd.com/read/28700099/potential-avenues-for-exercise-to-activate-episodic-memory-related-pathways-a-narrative-review
#16
REVIEW
Paul D Loprinzi, Meghan K Edwards, Emily Frith
Memory function plays an important role in activities of daily living, and consequently, quality and quantity of life. In this narrative review, we discuss the anatomical components of episodic memory, including the structure of the hippocampus and the routes of communication to and from this structure. We also highlight cellular traces of memory, such as the engram cell and pathway. To provide etiological insight, the biological mechanisms of episodic memory are discussed, including factors subserving memory encoding (e...
July 12, 2017: European Journal of Neuroscience
https://www.readbyqxmd.com/read/28683265/toward-a-neurocentric-view-of-learning
#17
REVIEW
Heather K Titley, Nicolas Brunel, Christian Hansel
Synaptic plasticity (e.g., long-term potentiation [LTP]) is considered the cellular correlate of learning. Recent optogenetic studies on memory engram formation assign a critical role in learning to suprathreshold activation of neurons and their integration into active engrams ("engram cells"). Here we review evidence that ensemble integration may result from LTP but also from cell-autonomous changes in membrane excitability. We propose that synaptic plasticity determines synaptic connectivity maps, whereas intrinsic plasticity-possibly separated in time-amplifies neuronal responsiveness and acutely drives engram integration...
July 5, 2017: Neuron
https://www.readbyqxmd.com/read/28667669/optogenetic-stimulation-of-dentate-gyrus-engrams-restores-memory-in-alzheimer-s-disease-mice
#18
Jennifer N Perusini, Stephanie A Cajigas, Omid Cohensedgh, Sean C Lim, Ina P Pavlova, Zoe R Donaldson, Christine A Denny
Alzheimer's disease (AD) is a prevalent neurodegenerative disorder characterized by amyloid-beta (Aβ) plaques and tau neurofibrillary tangles. APPswe/PS1dE9 (APP/PS1) mice have been developed as an AD model and are characterized by plaque formation at 4-6 months of age. Here, we sought to better understand AD-related cognitive decline by characterizing various types of memory. In order to better understand how memory declines with AD, APP/PS1 mice were bred with ArcCreER(T2) mice. In this line, neural ensembles activated during memory encoding can be indelibly tagged and directly compared with neural ensembles activated during memory retrieval (i...
October 2017: Hippocampus
https://www.readbyqxmd.com/read/28611219/inhibitory-engrams-in-perception-and-memory
#19
Helen C Barron, Tim P Vogels, Timothy E Behrens, Mani Ramaswami
Nervous systems use excitatory cell assemblies to encode and represent sensory percepts. Similarly, synaptically connected cell assemblies or "engrams" are thought to represent memories of past experience. Multiple lines of recent evidence indicate that brain systems create and use inhibitory replicas of excitatory representations for important cognitive functions. Such matched "inhibitory engrams" can form through homeostatic potentiation of inhibition onto postsynaptic cells that show increased levels of excitation...
June 27, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28585731/intracellular-determinants-of-hippocampal-cell-assembly-formation-during-associative-learning
#20
Jérôme Epsztein, Julie Koenig
No abstract text is available yet for this article.
August 1, 2017: Journal of Physiology
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