Topic
Engram
About: Engram is a research topic. Over the lifetime, 372 publications have been published within this topic receiving 15903 citations.
Papers published on a yearly basis
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Papers
TL;DR: An episodic model tested against speech production data from a word-shadowing task predicted the shadowing-response-time patterns, and it correctly predicted a tendency for shadowers to spontaneously imitate the acoustic patterns of words and nonwords.
Abstract: In this article the author proposes an episodic theory of spoken word representation, perception, and production. By most theories, idiosyncratic aspects of speech (voice details, ambient noise, etc.) are considered noise and are filtered in perception. However, episodic theories suggest that perceptual details are stored in memory and are integral to later perception. In this research the author tested an episodic model (MINERVA 2; D. L. Hintzman, 1986) against speech production data from a word-shadowing task. The model predicted the shadowing-response-time patterns, and it correctly predicted a tendency for shadowers to spontaneously imitate the acoustic patterns of words and nonwords. It also correctly predicted imitation strength as a function of "abstract" stimulus properties, such as word frequency. Taken together, the data and theory suggest that detailed episodes constitute the basic substrate of the mental lexicon. Early in the 20th century, Semon (1909/1923) described a memory theory that anticipated many aspects of contemporary theories (Schacter, Eich, & Tulving, 1978). In modem parlance, this was an episodic (or exemplar) theory, which assumes that every experience, such as perceiving a spoken word, leaves a unique memory trace. On presentation of a new word, all stored traces are activated, each according to its similarity to the stimulus. The most activated traces connect the new word to stored knowledge, the essence of recognition. The multiple-trace assumption allowed Semon's theory to explain the apparent permanence of specific memories; the challenge was also to create
1,553 citations
TL;DR: In this article, the authors found that the prefrontal engram cells, with support from hippocampal memory cells, became functionally mature with time and the basolateral amygdala remained functional with time.
Abstract: Episodic memories initially require rapid synaptic plasticity within the hippocampus for their formation and are gradually consolidated in neocortical networks for permanent storage. However, the engrams and circuits that support neocortical memory consolidation have thus far been unknown. We found that neocortical prefrontal memory engram cells, which are critical for remote contextual fear memory, were rapidly generated during initial learning through inputs from both the hippocampal–entorhinal cortex network and the basolateral amygdala. After their generation, the prefrontal engram cells, with support from hippocampal memory engram cells, became functionally mature with time. Whereas hippocampal engram cells gradually became silent with time, engram cells in the basolateral amygdala, which were necessary for fear memory, were maintained. Our data provide new insights into the functional reorganization of engrams and circuits underlying systems consolidation of memory.
942 citations
TL;DR: The evidence for persistent changes in intrinsic neuronal excitability — what the authors will call intrinsic plasticity — that is produced by training in behaving animals and by artificial patterns of activation in brain slices and neuronal cultures is considered.
Abstract: Modern theories of memory storage have largely focused on persistent, experience-dependent changes in synaptic function such as long-term potentiation and depression But in addition to these synaptic changes, certain learning tasks produce enduring changes in the intrinsic excitability of neurons by changing the function of voltage-gated ion channels, a change that can produce broader, even neuron-wide changes in synaptic throughput We will consider the evidence for persistent changes in intrinsic neuronal excitability — what we will call intrinsic plasticity — that is produced by training in behaving animals and by artificial patterns of activation in brain slices and neuronal cultures These intrinsic changes might function as part of the engram itself, or as a related phenomenon such as a trigger for the consolidation or adaptive generalization of memories
937 citations
TL;DR: It is suggested that once formed, an engram may exist in different states on the basis of their retrievability, and increased intrinsic excitability and synaptic plasticity work hand in hand to form engrams, and these mechanisms are also implicated in memory consolidation and retrieval processes.
Abstract: In 1904, Richard Semon introduced the term "engram" to describe the neural substrate for storing memories. An experience, Semon proposed, activates a subset of cells that undergo off-line, persistent chemical and/or physical changes to become an engram. Subsequent reactivation of this engram induces memory retrieval. Although Semon's contributions were largely ignored in his lifetime, new technologies that allow researchers to image and manipulate the brain at the level of individual neurons has reinvigorated engram research. We review recent progress in studying engrams, including an evaluation of evidence for the existence of engrams, the importance of intrinsic excitability and synaptic plasticity in engrams, and the lifetime of an engram. Together, these findings are beginning to define an engram as the basic unit of memory.
832 citations
TL;DR: Since associative learning, especially of the classical type, is well described at the phenomenological and operational level (Rescorla, 1988), it provides a favorable approach in the search for the neural substrate underlying learning and memory.
Abstract: The understanding of the physiology of learning is dominated by two basically different hypotheses. The deterministic view, following Hebb’s (1949) concept of the memory engram, presupposes a memory groove which is built during memory formation by the adaptive change of a relatively small number of reacting sites or switch points. These so-called ’switchpoint theories’ or ‘place theories’ assume that memory involves a discrete set of cells reserved for the special function of information storage (Young 1964; Eccles 1964; Ungar 1970). The non-deterministic or statistical theory is based on Lashley’s (1950) findings which suggest that all, or nearly all, stored information is distributed throughout the whole association cortex rather than by distinct association paths or centres. The individual neuronal switch points may then be involved in the storage of many different memory traces (John 1967, 1972). The two views are similar in that they take the adaptivity of single synapses between neurones as the basic modifiable component of the nervous system (Eccles and McIntyre 1953; Eccles 1964; Ungar 1970; John 1972). They differ, however, in their conception of the gross structure of the memory system. The crucial problem, then, is to locate the stored information. The spatio-temporal pattern of activity during memory formation produces a localised change in the excitability of specific neurones. It should be possible to find such neurones using the same techniques as have been employed for the location of units in the sensory integration centres.
715 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2026 | 3 |
| 2025 | 40 |
| 2024 | 91 |
| 2023 | 109 |
| 2022 | 132 |
| 2021 | 44 |