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Memory engram

Nicolas Rouleau, Lukasz M Karbowski, Michael A Persinger
Synthetic experimental substrates are indispensable tools which can allow researchers to model biological processes non-invasively in three-dimensional space. In this study, we investigated the capacities of an electroconductive material whose properties converge upon those of the brain. An electrically conductive material composed of carbohydrates, proteins, fats, ions, water, and trace amounts of other organic compounds and minerals was classically conditioned as inferred by electrophysiological measurements...
2016: PloS One
Anna Brancato, Gianluca Lavanco, Angela Cavallaro, Fulvio Plescia, Carla Cannizzaro
BACKGROUND: Emotionally salient experiences induce the formation of explicit memory traces, besides eliciting automatic or implicit emotional memory in rodents. This study aims at investigating the implementation of a novel task for studying the formation of limbic memory engrams as a result of the acquisition- and retrieval- of fear-conditioning - biased declarative memory traces, measured by animal discrimination of an "emotional-object". Moreover, by using this new method we investigated the potential interactions between stimulation of cannabinoid transmission and integration of emotional information and cognitive functioning...
October 6, 2016: Journal of Neuroscience Methods
Takahiro Yoshii, Hiroshi Hosokawa, Naoki Matsuo
Fear memory extinction has several characteristic behavioral features, such as spontaneous recovery, renewal, and reinstatement, suggesting that extinction training does not erase the original association between the conditioned stimulus (CS) and the unconditioned stimulus (US). However, it is unclear whether reactivation of the original physical record of memory (i.e., memory trace) is sufficient to produce conditioned fear response after extinction. Here, we performed pharmacogenetic neuronal activation using transgenic mice expressing hM3Dq DREADD (designer receptor exclusively activated by designer drug) under the control of the activity-dependent c-fos gene promoter...
September 14, 2016: Neuropharmacology
Ji-Song Guan, Jun Jiang, Hong Xie, Kai-Yuan Liu
Episodic memory in human brain is not a fixed 2-D picture but a highly dynamic movie serial, integrating information at both the temporal and the spatial domains. Recent studies in neuroscience reveal that memory storage and recall are closely related to the activities in discrete memory engram (trace) neurons within the dentate gyrus region of hippocampus and the layer 2/3 of neocortex. More strikingly, optogenetic reactivation of those memory trace neurons is able to trigger the recall of naturally encoded memory...
2016: Frontiers in Neural Circuits
Paul Marshall, Timothy W Bredy
A complete understanding of the fundamental mechanisms of learning and memory continues to elude neuroscientists. Although many important discoveries have been made, the question of how memories are encoded and maintained at the molecular level remains. To date, this issue has been framed within the context of one of the most dominant concepts in molecular biology, the central dogma, and the result has been a protein-centric view of memory. Here we discuss the evidence supporting a role for neuroepigenetic mechanisms, which constitute dynamic and reversible, state-dependent modifications at all levels of control over cellular function, and their role in learning and memory...
2016: NPJ Sci Learn
Masanori Nomoto, Noriaki Ohkawa, Hirofumi Nishizono, Jun Yokose, Akinobu Suzuki, Mina Matsuo, Shuhei Tsujimura, Yukari Takahashi, Masashi Nagase, Ayako M Watabe, Fusao Kato, Kaoru Inokuchi
Behavioural tagging is the transformation of a short-term memory, induced by a weak experience, into a long-term memory (LTM) due to the temporal association with a novel experience. The mechanism by which neuronal ensembles, each carrying a memory engram of one of the experiences, interact to achieve behavioural tagging is unknown. Here we show that retrieval of a LTM formed by behavioural tagging of a weak experience depends on the degree of overlap with the neuronal ensemble corresponding to a novel experience...
2016: Nature Communications
Asim J Rashid, Chen Yan, Valentina Mercaldo, Hwa-Lin Liz Hsiang, Sungmo Park, Christina J Cole, Antonietta De Cristofaro, Julia Yu, Charu Ramakrishnan, Soo Yeun Lee, Karl Deisseroth, Paul W Frankland, Sheena A Josselyn
Collections of cells called engrams are thought to represent memories. Although there has been progress in identifying and manipulating single engrams, little is known about how multiple engrams interact to influence memory. In lateral amygdala (LA), neurons with increased excitability during training outcompete their neighbors for allocation to an engram. We examined whether competition based on neuronal excitability also governs the interaction between engrams. Mice received two distinct fear conditioning events separated by different intervals...
July 22, 2016: Science
Dano J Morrison, Asim J Rashid, Adelaide P Yiu, Chen Yan, Paul W Frankland, Sheena A Josselyn
Memories are thought to be represented by discrete physiological changes in the brain, collectively referred to as an engram, that allow patterns of activity present during learning to be reactivated in the future. During the formation of a conditioned fear memory, a subset of principal (excitatory) neurons in the lateral amygdala (LA) are allocated to a neuronal ensemble that encodes an association between an initially neutral stimulus and a threatening aversive stimulus. Previous experimental and computational work suggests that this subset consists of only a small proportion of all LA neurons, and that this proportion remains constant across different memories...
July 12, 2016: Neurobiology of Learning and Memory
Meng Li, Jun Liu, Joe Z Tsien
Richard Semon and Donald Hebb are among the firsts to put forth the notion of cell assembly-a group of coherently or sequentially-activated neurons-to represent percept, memory, or concept. Despite the rekindled interest in this century-old idea, the concept of cell assembly still remains ill-defined and its operational principle is poorly understood. What is the size of a cell assembly? How should a cell assembly be organized? What is the computational logic underlying Hebbian cell assemblies? How might Nature vs...
2016: Frontiers in Neural Circuits
Mu-Ming Poo, Michele Pignatelli, Tomás J Ryan, Susumu Tonegawa, Tobias Bonhoeffer, Kelsey C Martin, Andrii Rudenko, Li-Huei Tsai, Richard W Tsien, Gord Fishell, Caitlin Mullins, J Tiago Gonçalves, Matthew Shtrahman, Stephen T Johnston, Fred H Gage, Yang Dan, John Long, György Buzsáki, Charles Stevens
The mechanism of memory remains one of the great unsolved problems of biology. Grappling with the question more than a hundred years ago, the German zoologist Richard Semon formulated the concept of the engram, lasting connections in the brain that result from simultaneous "excitations", whose precise physical nature and consequences were out of reach of the biology of his day. Neuroscientists now have the knowledge and tools to tackle this question, however, and this Forum brings together leading contemporary views on the mechanisms of memory and what the engram means today...
2016: BMC Biology
Sungmo Park, Emily E Kramer, Valentina Mercaldo, Asim J Rashid, Nathan Insel, Paul W Frankland, Sheena A Josselyn
The dentate gyrus (DG) is important for encoding contextual memories, but little is known about how a population of DG neurons comes to encode and support a particular memory. One possibility is that recruitment into an engram depends on a neuron's excitability (Han et al, 2009; Zhou et al, 2009; Choi et al, 2011; Sano et al, 2014). Here we manipulated excitability by overexpressing CREB in a random population of DG neurons and examined whether this biased their recruitment to an engram supporting a contextual fear memory...
May 17, 2016: Neuropsychopharmacology: Official Publication of the American College of Neuropsychopharmacology
Patrick Kaifosh, Attila Losonczy
We present a model for neural circuit mechanisms underlying hippocampal memory. Central to this model are nonlinear interactions between anatomically and functionally segregated inputs onto dendrites of pyramidal cells in hippocampal areas CA3 and CA1. We study the consequences of such interactions using model neurons in which somatic burst-firing and synaptic plasticity are controlled by conjunctive processing of these separately integrated input pathways. We find that nonlinear dendritic input processing enhances the model's capacity to store and retrieve large numbers of similar memories...
May 4, 2016: Neuron
Ji-Il Kim, Hye-Yeon Cho, Jin-Hee Han, Bong-Kiun Kaang
During past decades, the formation and storage principle of memory have received much attention in the neuroscience field. Although some studies have attempted to demonstrate the nature of the engram, elucidating the memory engram allocation mechanism was not possible because of the limitations of existing methods, which cannot specifically modulate the candidate neuronal population. Recently, the development of new techniques, which offer ways to mark and control specific populations of neurons, may accelerate solving this issue...
April 2016: Experimental Neurobiology
Birte Dietz, Denise Manahan-Vaughan
Long-term potentiation(LTP) and long-term depression(LTD) are key cellular processes that support memory formation. Whereas increases of synaptic strength by means of LTP may support the creation of a spatial memory 'engram', LTD appears to play an important role in refining and optimising experience-dependent encoding. A differentiation in the role of hippocampal subfields is apparent. For example, LTD in the dentate gyrus(DG) is enabled by novel learning about large visuospatial features, whereas in area CA1, it is enabled by learning about discrete aspects of spatial content, whereby, both discrete visuospatial and olfactospatial cues trigger LTD in CA1...
April 4, 2016: Neuropharmacology
Dheeraj S Roy, Autumn Arons, Teryn I Mitchell, Michele Pignatelli, Tomás J Ryan, Susumu Tonegawa
Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive memory decline and subsequent loss of broader cognitive functions. Memory decline in the early stages of AD is mostly limited to episodic memory, for which the hippocampus has a crucial role. However, it has been uncertain whether the observed amnesia in the early stages of AD is due to disrupted encoding and consolidation of episodic information, or an impairment in the retrieval of stored memory information. Here we show that in transgenic mouse models of early AD, direct optogenetic activation of hippocampal memory engram cells results in memory retrieval despite the fact that these mice are amnesic in long-term memory tests when natural recall cues are used, revealing a retrieval, rather than a storage impairment...
March 24, 2016: Nature
Howard Eichenbaum
For nearly a century, neurobiologists have searched for the engram-the neural representation of a memory. Early studies showed that the engram is widely distributed both within and across brain areas and is supported by interactions among large networks of neurons. Subsequent research has identified engrams that support memory within dedicated functional systems for habit learning and emotional memory, but the engram for declarative memories has been elusive. Nevertheless, recent years have brought progress from molecular biological approaches that identify neurons and networks that are necessary and sufficient to support memory, and from recording approaches and population analyses that characterize the information coded by large neural networks...
September 2016: Learning & Behavior
Stéphanie Trouche, Pavel V Perestenko, Gido M van de Ven, Claire T Bratley, Colin G McNamara, Natalia Campo-Urriza, S Lucas Black, Leon G Reijmers, David Dupret
The hippocampus provides the brain's memory system with a subset of neurons holding a map-like representation of each environment experienced. We found in mice that optogenetic silencing those neurons active in an environment unmasked a subset of quiet neurons, enabling the emergence of an alternative map. When applied in a cocaine-paired environment, this intervention neutralized an otherwise long-lasting drug-place preference, showing that recoding a spatial memory engram can alleviate associated maladaptive behavior...
April 2016: Nature Neuroscience
Thomas Stefanelli, Cristina Bertollini, Christian Lüscher, Dominique Muller, Pablo Mendez
Hippocampal neurons activated during encoding drive the recall of contextual fear memory. Little is known about how such ensembles emerge during acquisition and eventually form the cellular engram. Manipulating the activity of granule cells (GCs) of the dentate gyrus (DG), we reveal a mechanism of lateral inhibition that modulates the size of the cellular engram. GCs engage somatostatin-positive interneurons that inhibit the dendrites of surrounding GCs. Our findings reveal a microcircuit within the DG that controls the size of the cellular engram and the stability of contextual fear memory...
March 2, 2016: Neuron
Yurika Koga, Yuko Matsuo, Ryota Matsuo
Terrestrial pulmonates can form odor-aversion memories once a food odor is presented in combination with an aversive stimulus. Most of the olfactory information ascends via a tentacular ganglion located in the tip of the two pairs of tentacles, and is then transmitted to the higher olfactory center, the procerebrum. The procerebrum is the locus of memory storage and has been shown to be necessary for odor-aversion learning. However, it is unknown whether the procerebrum is the sole locus in which the memory engram resides...
February 2016: Zoological Science
Michael R Foy, Judith G Foy
One of the most prolific behavioral neuroscientists of his generation, Richard F. Thompson published more than 450 research articles during his almost 60-year career before his death in 2014. The breadth and reach of his scholarship has extended to a large multidisciplinary audience of scientists. The focal point of this article is arguably his most influential paper on cerebellar classical conditioning entitled "The Neurobiology of Learning and Memory" that appeared in Science in 1986 and has been cited 700 times since its publication...
January 28, 2016: Behavioral Neuroscience
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