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Angaben zur Quelle [Bearbeiten]

Autor     Lynn Nadel
Titel    The Hippocampus and Context Revisited
Sammlung    Hippocampal Place Fields : Relevance to Learning and Memory
Herausgeber    Sheri J.Y. Mizumori
Ort    Oxford
Verlag    Oxford University Press
Datum    26. February 2008
DOI    DOI: 10.1093/acprof:oso/9780195323245.001.0001
URL    GB

Literaturverz.   

no
Fußnoten    yes
Fragmente    11


Fragmente der Quelle:
[1.] Jm/Fragment 015 09 - Diskussion
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Although there is general consensus stipulating that the hippocampus plays a role in context effects (e.g., see Smith & Mizumori, 2006; Rudy et al., 2004; Gerwitz et al., 2000), a lack of cohesion arises concerning the nature of context itself, in particular the fact that there are multiple forms, and hence representations, of context, only one of which depends upon the hippocampus. [Nadel and Willner (1980) have argued that context representations formed in the hippocampus are essentially configural, being based on relations among the environmental features that comprise the physical lay-out of space. The authors further argued that because of this configural nature, learning about spatial context diverges in important respects from learning about isolated cues, or elements, within an environmental context. The authors further asserted that hippocampal damage would manifest as a lack of context-specificity, in the respect that learning should theoretically be inappropriately generalized to novel contexts.] [page 3]

[We argued that context representations formed in the hippocampus were fundamentally configural, being based on relations among the environmental features that comprised the physical lay-out of space. We further argued that because of this configural nature, learning about spatial context was different in important ways from learning about isolated cues, or elements, in the organism’s world2. [...]

A second idea we emphasized was that hippocampal damage would manifest as a lack of context specificity – learning would be inappropriately generalized to novel contexts.]

[page 4]

Although there is general agreement that the hippocampus plays a role in context effects, confusion arises from continued misunderstanding of the nature of context itself, in particular the fact that there are multiple forms, and hence representations, of context, only one of which depends upon the hippocampus.


[2 [...]]

Anmerkungen

Starting from the 2nd sentence it is clear that results of Nadel and Willner (1980) are presented. One might ask whether this presentation is not also taken from the source, but for the purpose here, only the first sentence is counted.

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[2.] Jm/Fragment 016 01 - Diskussion
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[Further, adopting conditioned fear paradigms in animals (e.g., Anagnostras et al., 1999, 2001; Fanselow, 1999, 2000), it has been found that; the hippocampus seems to] be necessary for the acquisition of context fear, and for the retrieval of such fear for days (or weeks) following initial training, but not for retrieval 28 days after training; and the acquisition of context fear itself depends upon the animal having had some previous exposure to the context prior to fear training. In the absence of such experience, context fear does not develop. Research using conditioned fear from studies by Rudy’s, as well as Fanselow’s group (Kim and Fanselow, 1992; Anagnostaras et al., 1999, 2001; Fanselow, 1999, 2000), has demonstrated two very important things: (1) the hippocampus seems to be necessary for acquisition of context fear, and for retrieval of such fear for some days (or weeks) after initial training, but not for retrieval 28 days after training; and (2) the acquisition of context fear itself depends upon the animal having had some exposure to the context before fear training starts. Absent such experience, context fear does not develop.
Anmerkungen

The source is not given.

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Thus, memories can lose their “context” dependence, becoming less “episodic” and more “semantic” in nature. As such, the “context” representation that supports [conditioned fear after several weeks is a representation based on elements present in the test situation rather than a configural representation of the whole.] More specifically, memories can lose their “context” dependence, becoming less “episodic” and more “semantic” in nature. [...]

[...]

[Instead of assuming that “memory” is either transferred from hippocampus to neocortex, or given independent status within neocortex after a period of requiring hippocampal help in retrieval,] one can best account for the data by assuming that the “context” representation that supports conditioned fear after several weeks is a representation based on elements in the test situation rather than a configural representation of the whole.

Anmerkungen

The copied text is continued on the next page: Jm/Fragment_017_01

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[As such, the “context” representation that supports] conditioned fear after several weeks is a representation based on elements present in the test situation rather than a configural representation of the whole.

Such an explanation mirrors findings pertaining to the ‘pre-exposure’ effect. In this case, when an animal is given fear training without some exposure to the training context prior to the introduction of the unconditioned stimulus, it fails to learn to associate shock with the “context” understood as the configuration of elements (and their spatial relations) in the chamber. This happens, according to Nadel, because exposure to the shock chamber is essential for the animal to acquire a configural representation of the context in the first place – what is termed a ‘cognitive map’ (O’Keefe & Nadel, 1978), or a contextual representation (Nadel & Willner, 1980). According to Nadel, such a finding parallels what happens over time within the realm of consolidation. Initial training (with pre-exposure) leads the animal to associate fear with the configurally-represented context. As such, the behavior depends upon the hippocampus as well as the amygdala. Over time, and as a direct consequence of what has been termed consolidation, the contextual binding weakens, leaving behind only linkages between elements of the chamber and the shock.

These considerations make it much easier to understand the existing literature concerning context and hippocampal lesion effects and why doubts still exist about hippocampal involvement in context learning (e.g., Gewirtz et al., 2000). When “normal” behavior depends upon a configural representation of context, hippocampal lesions will lead to impairment (Nadel, 2008). This should be the case for both acquisition and retention. When a task is used that can be solved with either a configural or an elemental representation of context, hippocampal lesions will not cause an obvious impairment; rather, special testing methods will have to be used to show that performance differs between animals with hippocampal lesions and control animals. The most obvious method would be to shift the test context.

[page 5]

[Instead of assuming that “memory” is either transferred from hippocampus to neocortex, or given independent status within neocortex after a period of requiring hippocampal help in retrieval,] one can best account for the data by assuming that the “context” representation that supports conditioned fear after several weeks is a representation based on elements in the test situation rather than a configural representation of the whole.

[page 6]

This story connects with what has been learned from studying the pre-exposure effect (cf. Fanselow’s work and Rudy’s work). When an animal is given fear training without some exposure to the training context before US introduction, it fails to learn to associate shock with the “context” understood as the configuration of elements (and their spatial relations) in the chamber. This happens because exposure to the shock chamber is essential for the animal to acquire a configural representation of the context in the first place – what we called a cognitive map (O’Keefe and Nadel, 1978), or a contextual representation (Nadel and Willner, 1980).

I believe that this parallels what happens over time in the consolidation domain. Initial training (with pre-exposure) leads the animal to associate fear with the configurally-represented context. As such, the behavior depends upon the hippocampus as well as the amygdala. Over time, and as a direct consequence of what has been called consolidation, the contextual binding weakens, leaving behind only linkages between elements of the chamber and the shock.

These considerations make it much easier to understand the existing literature on hippocampal lesion effects and context and why doubts still exist about hippocampal involvement in context learning (e.g., Gewirtz et al., 2000). When “normal” behavior depends upon a configural representation of context, hippocampal lesions will lead to impairment. This should be the case in both acquisition and retention. When a task is used that can be solved with either a configural or an elemental representation of context, hippocampal lesions will not cause an obvious impairment; rather, special testing methods will have to be used to show that the basis of performance differs between animals with hippocampal lesions and control animals. The most obvious such method would be to shift the test context.

Anmerkungen

Nadel (2008) is mentioned in the text, but it is not clear to the reader at all that the entire page is copied from the source, which is also not listed in the bibliography.

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[5.] Jm/Fragment 018 01 - Diskussion
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[Paradoxically, animals with hippocampal lesions should theoretically be less] affected by such a shift than intact animals. In the case of conditioned fear, for example, hippocampally-lesioned rats should show greater-than-normal fear in an out-of-context test. Indeed, Nadel (1968) demonstrated this effect; rats with dorsal hippocampal lesions tested in context B for fear of a CS paired with shock in context A actually showed more fear than did control rats. This parallels observations of Penick and Solomon (1991), and is consistent with the report by Good and Honey (1991) showing that hippocampal lesions impaired rats’ ability to learn that a stimulus was reinforced in one context but not in another (see also Lehmann et al., 2005; but see Hall et al., 1996). It is also consistent with the recent findings that hippocampal inactivation impairs the context specificity of latent inhibition (Maren & Holt, 2000), and extinction (Corcoran et al., 2005; Hobin et al., 2006), and that reinstatement of conditioned fear in humans is context specific (LaBar & Phelps, 2005). Paradoxically, animals with hippocampal lesions should be less affected by such a shift than intact animals. In the case of conditioned fear, for example, hippocampal-lesioned rats should show greater-than-normal fear in an out-of-context test. In my doctoral work (Nadel, 1968) I showed exactly this effect, but did not at that time understand what it was telling me. Rats with dorsal hippocampal lesions tested in context B for fear of a CS paired with shock in context A actually showed more fear than did control rats. This finding parallels the Penick and Solomon (1991) result noted above, and is consistent with the report by Good and Honey (1991) showing that hippocampal lesions impaired rats’ ability to learn that a stimulus was reinforced in one context but not in another (see also Lehmann et al., 2005; but see Hall et al., 1996). It is also consistent with the recent findings that hippocampal inactivation impairs the context specificity of latent inhibition (Maren and Holt, 2000), and extinction (Corcoran et al., 2005; Hobin et al., 2006), and that reinstatement of conditioned fear in humans is context specific (LaBar & Phelps, 2005).
Anmerkungen

The source is given on the previous page, but with no indication that the passage here is taken from it more or less verbatim.

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1.2.4 Context Recognition- The Key to Reconsolidation

[Context plays an integral role in the consolidation of a memory trace.] The impact of hippocampal lesions on the retention of a context-based task depend upon when retention is tested, and upon whether or not the animal was reminded of the context before retention was tested.

[page 6]

The impact of hippocampal lesions on retention of a context-based task will depend on when retention is tested, and on whether or not the animal was reminded of the context before retention was tested.

[page 9]

CONTEXT RECOGNITION – THE KEY TO RECONSOLIDATION

Anmerkungen

Beginning of a longer passage copied from Nadel (2008). See: Jm/Fragment_024_01

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[As proposed by Nadel and colleagues above, after some weeks during which a rat is] not returned to the training context, its configural representation of that context weakens, and elemental contextual representations take over. In the absence of reminders that bring the context back into the frame, hippocampal lesions yield little or no effect. However, as various investigators (e.g., Debiec et al., 2002; Land et al., 2000) have reported in the reconsolidation literature; if animals are reminded of the context before lesions are made, then these lesions subsequently serve to impair retention.

Creating an entirely new representation in response to deciding that one is in a new environment differs from updating an existing representation based on some local change (Nadel, 2008). According to Nadel, this assertion is fundamental to the distinction between memory “consolidation” and memory “reconsolidation”. It has long been assumed that a time-dependent stabilization process unfolds after the initial acquisition of a memory (Müller & Pilzecker, 1900). During this time period, termed the “consolidation” interval, memories can be disrupted by new learning experiences, cerebral trauma, hypothermia, electroconvulsive shock, and so on. This idea was initially framed within both physiological and psychological terms, and included the possibility that the content of the memory might itself be transformed during consolidation (Burnham, 1903). Hebb (1949) isolated the physiological process underlying consolidation, thereby providing a comprehensive understanding concerning how exactly memories become stabilized. Hebb assumed that memories are isolated in the brain through changes in synaptic efficacy, and that these changes depend upon complex cellular and molecular mechanisms that lead to structural alterations underpinning potentiated synaptic function. According to Hebb these changes unfolded within the same cell assemblies initially activated by the experience, possibly through reverberations within these assemblies. Study of patient H.M., however, suggested that, in terms of memory for life’s episodes, consolidation involves a shift wherein brain structures are critical for memory retrieval.

[page 6]

As we argued above, after some weeks during which a rat is not returned to the training context, its configural representation of that context weakens, and elemental contextual representations take over. In the absence of reminders that bring the context back into the picture, hippocampal lesions have little or no effect. But, as Land et al., (2000) have shown, if animals are reminded of the context before lesions are made, these lesions can impair retention (for a similar result see Debiec et al., 2002).

[page 9]

Creating an entirely new representation in response to deciding that one is in a new environment is quite different than updating an existing representation on the basis of some local change. I believe this difference is fundamental to the distinction between memory “consolidation” and memory “reconsolidation”. [...]

It has long been assumed that a time-dependent stabilization process unfolds after initial acquisition of a memory (Muller and Pilzecker, 1900). During this time period, termed the “consolidation” interval, memories can be disrupted by new learning experiences, blows to the head, hypothermia, electroconvulsive shock, etc. This idea was initially couched in both physiological and psychological terms, and included the possibility that the content of the memory might itself be transformed during consolidation (cf., Burnham, 1903). Although these early writers assumed that consolidation involved a physiological process, the first detailed proposal came from Hebb (1949), who provided a way of understanding how memories could become stabilized. Hebb assumed that memories are captured in the brain through changes in synaptic efficacy, and that these changes depend upon complex cellular and molecular mechanisms that lead to structural alterations underpinning potentiated synaptic function. In Hebb’s view these changes unfolded within the same cell assemblies initially activated by the experience, possibly through reverberations within these assemblies. Study of patient H.M. (Scoville and Milner, 1957), however, suggested that, at least for episodic memory, consolidation involves a shift in which brain structures are critical for memory retrieval.

Anmerkungen

The source is referenced, but is not clear for the reader that the entire page is taken from it including various references to older literature.

The phrase "As proposed by Nadel and colleagues above" seems odd in a thesis by another author.

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[Thus began a long tradition of linking what has] come to be termed systems-level memory consolidation to a shift from hippocampal to neocortical dominance in memory retrieval. The consolidation period was assumed to end when the hippocampal system was no longer essential in retrieval.

It was within this context that the concept of memory reconsolidation first emerged. A number of investigators in the 1960s and 1970s, unconvinced by the concept of consolidation, argued instead that memories were always open to alteration and/or disruption as long as they were in an active state (Lewis, 1979; Misanin et al., 1968). Memories could be reconverted into an active state through “reminders” such as exposing the organism to the CS used in the learning task, or the context in which learning took place. These ideas, though supported by several well-replicated findings, were neglected in favour of consolidation.

The notion of reconsolidation re-emerged in two labs: Sara and colleagues (e.g., Przybyslawski & Sara., 1997; Sara, 2000) and Nader, LeDoux and their colleagues (Nader et al., 2000) which both demonstrated that reminders could return well-consolidated memories for maze learning and fear conditioning, respectively, back to a fragile, labile state, and that these newly-fragile memories could be disrupted by the systemic injection of MK-801 (an NMDA channel blocker), or protein synthesis inhibitors into the amygdala, respectively. There followed a proliferation of studies demonstrating the robust nature of ‘reconsolidation’, its presence in a wide variety of species and learning situations, how it is differentiated from consolidation, and what some of the boundary conditions are that constrain it (refer to Moore & Roche, 2007, for a comprehensive account of the literature).

In a similar vein, a tradition of research using human subjects has demonstrated seemingly similar malleability in what should have been consolidated episodically mediated memories (e.g., Loftus, 2005). Much of this research employs a standard procedure wherein subjects are exposed to a complex event, and are later given misinformation concerning some detail of that event.

Thus began a long tradition of linking what has come to be called "systems-level memory consolidation" to a shift from hippocampal to neocortical dominance in memory retrieval. The consolidation period was assumed to end when the hippocampal system was no longer essential in retrieval.

It was in this context that the idea of memory reconsolidation first emerged. A number of investigators in the 1960s and 1970s, unconvinced by the consolidation idea, argued instead that memories were always open to alteration and/or disruption so long as they were in an active state (see Misanin et al., 1968, Lewis, 1979). Memories could be brought back to an active state through “reminders” such as exposing the organism to the CS used in the learning task, or the context in which learning took place. These ideas, though backed by several well-replicated findings, were pushed aside by the consolidation bandwagon[, for reasons that would be of interest in an article on the history of science, but that are beyond the scope of this effort.]

The notion of reconsolidation re-emerged in two labs: Sara and her colleagues (Przybyslawski and Sara, 1997; Sara, 2000) and Nader, LeDoux and their colleagues (Nader et al., 2000) showed that reminders could bring well-consolidated memories for maze learning and fear conditioning, respectively, back to a fragile state, and that these newly-fragile memories could be disrupted by the systemic injection of MK-801 (an NMDA receptor antagonist), or protein synthesis inhibitors into the amygdala, respectively. There has followed a torrent of studies demonstrating the robust nature of reconsolidation, its presence in a wide variety of species and learning situations, the ways in which it is differentiated from consolidation, and some of the boundary conditions that constrain it. [...]

At the same time, a tradition of research using human subjects has demonstrated apparently similar malleability in supposedly consolidated memories (see Loftus, 2005). Much of this work uses a standard procedure: subjects are exposed to a complex event, then some time later they are given misinformation about some detail of that event.

Anmerkungen

The source is not referenced.

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[When subsequently asked to recall the event quite often the] misinformation rather than the original detail is remembered. One thing that distinguishes this work on human memory from the animal work discussed previously is the absence of any systematic manipulation of specific reminders.

With the intention of merging these two animal and human based findings, Nadel and colleagues recently developed a paradigm to study reconsolidation in human episodic memory that depends upon reminding subjects about what they previously learned (Hupbach et al., 2007). In this paradigm, subjects are initially trained on a “list” of objects. These everyday objects are kept in a blue basket and presented one by one to the subject. After all 20 objects are presented, the subject is asked to verbally “recall” the list. This training sequence is continued until the subject recalls at least 18 of the 20 objects (in any sequence). Typically this takes fewer than four training trials. Two days later subjects return to the laboratory and are divided into two groups. Subjects in one group are reminded of their previous training experience, whereas subjects in the other group are not. Subsequently, a second “list” of objects is learned, albeit in a different manner. The objects on this second list are laid out on a table instead of being contained in a basket. Following the learning of this second list recall for both lists is tested either immediately or two days later. In one study, recall of List 1 was tested first, followed by List 2, and in another study recall of List 2 was tested first, followed by List 1. In both studies retrieval performance of subjects that had been reminded was contrasted with subjects that had not.

The results emanating from this research stream can be summarized as follows (see Hupbach et al., 2007 for a more detailed account): if, and only if, a reminder was given prior to the learning of List 2, subjects inter-mixed items from List 2 into List 1 when asked to recall List 1. In another study these authors showed that this result is found only when recall is tested 2 days later. Intrusions from List 1 into List 2 recall were never observed, whether List 2 is recalled first or second, immediately or 2 days later.

[page 9]

When subsequently asked to recall the event quite often the misinformation rather than the original detail is remembered. One thing that distinguishes this important work on human memory from the animal work just discussed is the absence of any systematic manipulation of specific reminders.

In the hope of bringing these literatures together we have recently developed a paradigm to study reconsolidation in human episodic memory that depends on reminding the subjects about what they previously learned (Hupbach et al., 2007). Subjects are initially trained on a “list” of objects. These objects -- such things as a pencil, comb, or other similarly sized common object -- are kept in a blue basket and presented one by one to the subject. After all 20 objects are presented the subject is asked to verbally “recall” the

[page 10]

list. This training sequence is continued until the subject recalls at least 17 of the 20 objects (in any order) or for a maximum of four learning trials.

Two days later subjects return to the laboratory and are divided into two groups. Subjects in one group are reminded of their previous training experience, subjects in the other group are not. Then, a second “list” of objects is learned, but in a different way. The objects on this second list are arrayed on a table instead of being contained in a basket. Following the learning of this second list we test for recall of both lists either immediately or 2 days later. In one study we tested recall of list 1 and in another study we tested recall of list 2. In both studies we contrasted subjects twho had been reminded with subjects who had not.

The results can be summarized as follows (see Hupbach et al., for a full description of this study): if, and only if, a reminder is given prior to the learning of list 2, subjects will “intrude” items from list 2 into list 1 when asked to recall list 1 (Fig. 1-1A). Additionally we showed that this result occurs only when recall is tested 2 days later (Fig. 1- 1B). It is not observed when recall is tested immediately. Intrusions from list 1 into list 2 recall are never seen, regardless of whether list 2 is recalled immediately or second, immediately or 2 days later (see Fig. 1-1C).

Anmerkungen

It is clear from the text that the work of Nadel et al. is described here. It is not clear from the text, however, that this is done following the same structure and many formulations of Nadel (2008).

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[Nadel and colleagues] interpreted these results as indicative that the reminder presented prior to List 2 learning reactivated the memory trace for List 1, and thereby triggered an “update” mechanism which caused the subject to confuse the List 2 and List 1 objects. In the absence of the reminder, the subjects treated List 2 learning and List 1 learning as separate episodes and intrusions did not occur.

This research team, more recently, has begun to explore exactly what kinds of reminders play a critical role in initiating this “update” mechanism (Hupbach et al., 2008). In the original study the reminder involved returning the subject back to the same context, with the same Experimenter, who asked a leading question about the List 1 training experience. The no-reminder group was brought to a different context, with a different Experimenter, and was not asked about List 1 training. In the most recent of such work, these authors systematically manipulated the nature of the “reminders” available to the subjects prior to learning List 2. In one set of studies, only one of the three reminder cues was presented: the original training context, the original Experimenter, or the leading question about the basket in which List 1 objects were kept. Results revealed that only the group that received a context reminder showed the memory updating effect. The other two groups showed few if any intrusions of List 2 items into List 1 memory, thereby indicating that updating had not occurred in these groups.

Furthermore, in a second set of studies, two of the three cues were provided, either context plus Experimenter, context plus question, or Experimenter plus question, with the intention of investigating the possibility that the failure of the Experimenter or Question to initiate an updating process might have reflected that fact that these are weak cues compared to context, and that by combining these two weaker cues, updating would be demonstrated. Once again, only the provision of a context reminder, in combination with either the Experimenter or the Question, elicited updating.

[page 10]

We interpret these results as showing that the reminder prior to list 2 learning reactivates the memory of list 1, and triggers an “update” mechanism that causes the subject to conflate the list 2 and list 1 objects. Absent the reminder the subjects treat list 2 learning and list 1 learning as separate episodes and intrusions do not occur.

We have more recently started to explore exactly what kinds of reminders play a critical role in initiating this “update” mechanism (Hupbach et al., submitted). In the original study the reminder involved bringing the subject back to the same context, with the same experimenter, who asked a leading question about the list 1 training experience. The no-reminder group was

[page 11]

brought to a different context, with a different experimenter, and was not asked about list 1 training.

In our most recent work we systematically manipulated the nature of the “reminders” available to the subjects prior to learning list 2. In one set of studies we provided only one of the three reminder cues: the original training context, the original experimenter, or the leading question about the basket in which list 1 objects were kept. Figure 1-2A shows the results of these manipulations: only the group that received a context reminder showed the memory updating effect. The other two groups showed few if any intrusions of list 2 items into list 1 memory, indicating that updating had not occurred in these groups.

In a second set of studies we provided two of the three cues, either context plus experimenter, context plus question, or experimenter plus question. We wanted to explore the possibility that the failure of the Experimenter or Question to initiate an updating process might have reflected the fact that these are weak cues compared to context, and that by combining these two weaker cues we would be able to demonstrate updating. Figure 1-2B shows that this was not the case. Once again, only the provision of a context reminder, in combination with either the Experimenter or the Question, elicited updating.

Anmerkungen

It is clear from the text that here the work of Nadel et al. is described. It is not clear to the reader at all, that this description follows the structure and many formulations of Nadel (2008).

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(Hindemith) Schumann

[11.] Jm/Fragment 028 01 - Diskussion
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[That these conditions are effective is hardly] surprising since the previous study had shown that context alone is enough to trigger updating.

This set of experiments demonstrates that reconsolidation, as reflected in memory updating effects dependent upon reminding, can be observed in human learning. They further show that such updating only occurs when the context is part of the reminder manipulation, at least in the experimental conditions of these aforementioned studies. Nadel and colleagues conjecture that these results support the idea that context plays a unique role in determining how the memory system behaves. Thus, when in the same context – updating and transformation of an existing memory trace ensues, but when in a new context, an entirely new memory representation is formed.

Thus, it appears that context is an integral component of episodic memory. It is, however, more than just a component of such memory. It also seems to play a determining role in the dynamics of the episodic memory system as a whole. To the extent to which this is the case, further study concerning how context is represented physiologically should greatly enhance our understanding of human memory.

That these conditions are effective is hardly surprising since the previous study had shown that context alone is enough to trigger updating.

This set of experiments demonstrates that reconsolidation, as reflected in memory updating effects dependent upon reminding, can be observed in human learning. They further show that such updating only occurs when the context is part of the reminder manipulation, at least in the experimental conditions of our studies. We believe these results support the idea that context plays a unique role in determining how the memory system behaves. Put most directly: when in the same context, an existing representation is updated and transformed, but when the organism is in a new context, an entirely new representation is created.

CONCLUSIONS

Context is a critical component of episodic memory. It is, however, more than just a component of such memory. It also seems to play a determining role in the dynamics of the episodic memory system as a whole. To the extent to which this is the case, further study of how context is represented physiologically should greatly enhance our understanding of human memory.

Anmerkungen

While it is clear to the reader that the first two paragraphs are describing the work of Nadel et al. the third paragraph is presented to the reader as a conclusion of the author.

That the structure of all three paragraphs as well as many formulations are taken from Nadel (2008) is not clear to the reader at all.

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(Hindemith) Schumann

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