scholarly journals Theories of episodic memory

2001 ◽  
Vol 356 (1413) ◽  
pp. 1395-1408 ◽  
Author(s):  
Andrew R. Mayes ◽  
Neil Roberts
Keyword(s):  
Episodic Memory ◽  
Medial Temporal Lobe ◽  
Functional Neuroimaging ◽  
Memory Storage ◽  
Visual Object ◽  
Medial Temporal Lobes ◽  
Temporal Lobes ◽  
Episodic Information ◽  
Encoding And Retrieval

Theories of episodic memory need to specify the encoding (representing), storage, and retrieval processes that underlie this form of memory and indicate the brain regions that mediate these processes and how they do so. Representation and re–representation (retrieval) of the spatiotemporally linked series of scenes, which constitute an episode, are probably mediated primarily by those parts of the posterior neocortex that process perceptual and semantic information. However, some role of the frontal neocortex and medial temporal lobes in representing aspects of context and high–level visual object information at encoding and retrieval cannot currently be excluded. Nevertheless, it is widely believed that the frontal neocortex is mainly involved in coordinating episodic encoding and retrieval and that the medial temporal lobes store aspects of episodic information. Establishing where storage is located is very difficult and disagreement remains about the role of the posterior neocortex in episodic memory storage. One view is that this region stores all aspects of episodic memory ab initio for as long as memory lasts. This is compatible with evidence that the amygdala, basal forebrain, and midbrain modulate neocortical storage. Another view is that the posterior neocortex only gradually develops the ability to store some aspects of episodic information as a function of rehearsal over time and that this information is initially stored by the medial temporal lobes. A third view is that the posterior neocortex never stores these aspects of episodic information because the medial temporal lobes store them for as long as memory lasts in an increasingly redundant fashion. The last two views both postulate that the medial temporal lobes initially store contextual markers that serve to cohere featural information stored in the neocortex. Lesion and functional neuroimaging evidence still does not clearly distinguish between these views. Whether the feeling that an episodic memory is familiar depends on retrieving an association between a retrieved episode and this feeling, or by an attribution triggered by a priming process, is unclear. Evidence about whether the hippocampus and medial temporal lobe cortices play different roles in episodic memory is conflicting. Identifying similarities and differences between episodic memory and both semantic memory and priming will require careful componential analysis of episodic memory.

scholarly journals Delay-dependent contributions of medial temporal lobe regions to episodic memory retrieval

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Maureen Ritchey ◽  
Maria E Montchal ◽  
Andrew P Yonelinas ◽  
Charan Ranganath
Keyword(s):  
Episodic Memory ◽  
Medial Temporal Lobe ◽  
Functional Neuroimaging ◽  
Contextual Information ◽  
Medial Temporal Lobes ◽  
Temporal Lobes ◽  
Pattern Similarity ◽  
Delayed Recognition ◽  
Delay Dependent ◽  
Over Time

The medial temporal lobes play an important role in episodic memory, but over time, hippocampal contributions to retrieval may be diminished. However, it is unclear whether such changes are related to the ability to retrieve contextual information, and whether they are common across all medial temporal regions. Here, we used functional neuroimaging to compare neural responses during immediate and delayed recognition. Results showed that recollection-related activity in the posterior hippocampus declined after a 1-day delay. In contrast, activity was relatively stable in the anterior hippocampus and in neocortical areas. Multi-voxel pattern similarity analyses also revealed that anterior hippocampal patterns contained information about context during item recognition, and after a delay, context coding in this region was related to successful retention of context information. Together, these findings suggest that the anterior and posterior hippocampus have different contributions to memory over time and that neurobiological models of memory must account for these differences.

scholarly journals Hippocampal Volume Influences The Correlations Between White Matter Disruption and Tau Protein in aMCI and mild AD

2020 ◽  
Author(s):  
Thamires Naela Cardoso Magalhães ◽  
Raphael Fernandes Casseb ◽  
Christian Luiz Baptista Gerbelli ◽  
Luciana Ramalho Pimentel-Silva ◽  
Mateus Henrique Nogueira ◽  
...  
Keyword(s):  
White Matter ◽  
Medial Temporal Lobe ◽  
Hippocampal Volume ◽  
Tau Proteins ◽  
Cortical Atrophy ◽  
Medial Temporal Lobes ◽  
Temporal Lobes ◽  
Prodromal Ad ◽  
Transentorhinal Cortex

Abstract Background: Alzheimer’s disease (AD) is classically considered a grey matter (GM) disease that starts in the transentorhinal cortex and spreads to limbic and neocortical regions. However, white matter (WM) damage could be more severe and widespread than expected cortical atrophy. The role of AD biomarkers and WM integrity throughout the brain is unclear, especially in amnestic Mild Cognitive Impairment (aMCI) patients, a possible prodromal AD dementia stage. If WM damage can be detected even before the development of cortical atrophy and overt dementia and in the AD process, Aβ42 Tau (and its phosphorylated form) could directly affect WM. Methods: We analyzed in this study 183 individuals - 48 aMCI in the AD continuum (altered CSF Aβ42), 30 patients with very mild or mild AD dementia and 105 normal controls. All subjects underwent neuropsychological evaluation and MRI exams. aMCI and mild AD individuals were also submitted to CSF puncture to evaluate AD biomarkers.Results: We observed several significant differences in WM integrity regarding the DTI measures between individuals and we found significant correlations between fornix and right cingulum hippocampal tracts and Tau and p-Tau proteins. Conclusions: We hypothesize that significant correlations with tracts anatomically far from more well-established GM atrophic regions, like medial temporal lobes, would support a more direct effect of pathological proteins on WM, whereas medial temporal lobe (MTL) correlations would favor WD and/or a direct spreading of pathology from the hippocampus.

Imaging the Networks of Encoding, Consolidation, and Retrieval

2017 ◽  
Author(s):  
Andrew C. Papanicolaou ◽  
Nicole Shay ◽  
Christen M. Holder
Keyword(s):  
Neuronal Networks ◽  
Functional Neuroimaging ◽  
Medial Temporal Lobes ◽  
Temporal Lobes ◽  
Spontaneous Retrieval ◽  
Encoding And Retrieval

In this chapter, the authors examine the contributions of the functional neuroimaging literature to the specification of the neuronal networks of the mnemonic operations of encoding, consolidation, and retrieval. Although the most basic expectation regarding the involvement of parts of the medial temporal lobes, such as the hippocampus, in these operations was not consistently supported by the results of the neuroimaging studies reviewed, other expectations, such as the material-specific lateralization of activation were adequately supported. The several reasons that account for the limited contributions of neuroimaging to the neurophysiology of memory thus far, ranging from constraints imposed by the nature of the mnemonic operations (e.g., the fact that encoding and retrieval occur in tandem) to practical ones (e.g., difficulties in studying spontaneous retrieval), are outlined.

Does the Medial Temporal Lobe Bind Phonological Memories?

2001 ◽  
Vol 13 (5) ◽  
pp. 593-609 ◽  
Author(s):  
Raymond Knott ◽  
William Marslen-Wilson
Keyword(s):  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Lexical Representation ◽  
Phonological Memory ◽  
Distinctive Pattern ◽  
Medial Temporal Lobes ◽  
Phonological Representations ◽  
Temporal Lobes ◽  
Phonological Errors

The medial temporal lobes play a central role in the consolidation of new memories. Medial temporal lesions impair episodic learning in amnesia, and disrupt vocabulary acquisition. To investigate the role of consolidation processes in phonological memory and to understand where and how, in amnesia, these processes begin to fail, we reexamined phonological memory in the amnesic patient HM. While HM's word span performance was normal, his supraspan recall was shown to be markedly impaired, with his recall characterized by a distinctive pattern of phonological errors, where he recombined phonemes from the original list to form new response words. These were similar to errors observed earlier for patients with specifically semantic deficits. Amnesic Korsakoff's patients showed a similar, though much less marked, pattern. We interpret the data in terms of a model of lexical representation where temporal lobe damage disrupts the processes that normally bind semantic and phonological representations.

Visual Working Memory Is Impaired when the Medial Temporal Lobe Is Damaged

2006 ◽  
Vol 18 (7) ◽  
pp. 1087-1097 ◽  
Author(s):  
Ingrid R. Olson ◽  
Katherine Sledge Moore ◽  
Marianna Stark ◽  
Anjan Chatterjee
Keyword(s):  
Working Memory ◽  
Medial Temporal Lobe ◽  
Memory Load ◽  
Short Term ◽  
Medial Temporal Lobes ◽  
Temporal Lobes ◽  
Impaired Memory ◽  
Rehearsal Strategies ◽  
Verbal Component

The canonical description of the role of the medial temporal lobes (MTLs) in memory is that short-term forms of memory (e.g., working memory [WM]) are spared when the MTL is damaged, but longer term forms of memory are impaired. Tests used to assess this have typically had a heavy verbal component, potentially allowing explicit rehearsal strategies to maintain the WM trace over the memory delay period. Here we test the hypothesis that the MTL is necessary for visual WM when verbal rehearsal strategies are difficult to implement. In three patients with MTL damage we found impairments in spatial, face, and color WM, at delays as short as 4 sec. Impaired memory could not be attributed to memory load or perceptual problems. These findings suggest that the MTLs are critical for accurate visual WM.

scholarly journals Hippocampal Volume Influences the Correlations Between White Matter Disruption and Tau Protein in aMCI and mild AD

2020 ◽  
Author(s):  
Thamires Naela Cardoso Magalhães ◽  
Raphael Fernandes Casseb ◽  
Christian Luiz Baptista Gerbelli ◽  
Mateus Henrique Nogueira ◽  
Luciana Ramalho Pimentel-Silva ◽  
...  
Keyword(s):  
Medial Temporal Lobe ◽  
Hippocampal Volume ◽  
Cortical Atrophy ◽  
Medial Temporal Lobes ◽  
Temporal Lobes ◽  
Prodromal Ad ◽  
Transentorhinal Cortex ◽  
The Brain ◽  
Normal Controls

Abstract BackgroundAlzheimer’s disease (AD) is classically considered a grey matter (GM) disease that starts in transentorhinal cortex and spread to limbic and neocortical regions. However, withe matter (WM) damage could be more severe and widespread than expected cortical atrophy. It is not clear the role of AD biomarkers and WM integrity throughout the brain, especially including amnestic Mild Cognitive Impairment (aMCI) patients, a possible prodromal AD dementia stage, if WM damage can be detected even before the development of cortical atrophy and overt dementia and in AD process, Aβ42 Tau (and its phosphorylated form) could directly affect WM.MethodsWe analyzed in this study 183 individuals - 48 aMCI in the AD continuum (altered CSF Aβ42), 30 patients with very mild or mild AD dementia and 105 normal controls. All subjects underwent neuropsychological evaluation and MRI exam. aMCI and mild AD individuals were also submitted to CSF puncture to evaluate AD biomarkers.ResultsWe observed several significant differences in WM integrity regarding the DTI measures between individuals and we found significant correlations between fornix and right cingulum hippocampal tracts and Tau and p-Tau proteins.ConclusionsWe hypothesize that significant correlations with tracts anatomically far from more well-established GM atrophic regions, like medial temporal lobes, would support a more direct effect of pathological proteins on WM, whereas medial temporal lobe (MTL) correlations would favor WD and/or a direct spreading of pathology from hippocampus.

scholarly journals Medial Temporal Lobe Activity during Source Retrieval Reflects Information Type, not Memory Strength

2010 ◽  
Vol 22 (8) ◽  
pp. 1808-1818 ◽  
Author(s):  
Rachel A. Diana ◽  
Andrew P. Yonelinas ◽  
Charan Ranganath
Keyword(s):  
Medial Temporal Lobe ◽  
Declarative Memory ◽  
Memory Strength ◽  
Medial Temporal Lobes ◽  
Temporal Lobes ◽  
Parahippocampal Cortex ◽  
Episodic Information ◽  
Different Types ◽  
Contextual Association ◽  
Source Retrieval

The medial temporal lobes (MTLs) are critical for episodic memory but the functions of MTL subregions are controversial. According to memory strength theory, MTL subregions collectively support declarative memory in a graded manner. In contrast, other theories assert that MTL subregions support functionally distinct processes. For instance, one view is that perirhinal cortex (PRc) processes item information, parahippocampal cortex (PHc) processes context information, and the hippocampus binds item and context. Here, we report two experiments that tested competing predictions from these models. In these studies, subjects encoded color–word associations by imagining color either as a contextual association (context detail condition) or as a feature of the item to be encoded (item detail condition). Results showed that encoding color information as an item detail improved source recognition in amnesic patients with recollection deficits. Furthermore, event-related fMRI data from healthy subjects revealed PRc activation associated with successful retrieval of item details, whereas activation in the hippocampus and PHc was associated with recollection-based source retrieval. The qualitatively different patterns of results observed in PRc and hippocampus/PHc are inconsistent with a memory strength account and are consistent with the idea that different MTL regions process different types of episodic information.

scholarly journals Triple Dissociation in the Medial Temporal Lobes: Recollection, Familiarity, and Novelty

2006 ◽  
Vol 96 (4) ◽  
pp. 1902-1911 ◽  
Author(s):  
S. M. Daselaar ◽  
M. S. Fleck ◽  
R. Cabeza
Keyword(s):  
Medial Temporal Lobe ◽  
Memory Performance ◽  
Parahippocampal Gyrus ◽  
Medial Temporal Lobes ◽  
Temporal Lobes ◽  
Retrieval Processes ◽  
Individual Trial ◽  
Memory Signals ◽  
Magnetic Resonance Imaging Mri ◽  
Left Parietal Cortex

Memory for past events may be based on retrieval accompanied by specific contextual details (recollection) or on the feeling that an item is old (familiarity) or new (novelty) in the absence of contextual details. There are indications that recollection, familiarity, and novelty involve different medial temporal lobe subregions, but available evidence is scarce and inconclusive. Using functional magnetic resonance imaging (MRI), we isolated retrieval-related activity associated with recollection, familiarity, and novelty by distinguishing between linear and nonlinear oldness functions derived from recognition confidence levels. Within the medial temporal lobes (MTLs), we found a triple dissociation among the posterior half of the hippocampus, which was associated with recollection, the posterior parahippocampal gyrus, which was associated with familiarity, and anterior half of the hippocampus and rhinal regions, which were associated with novelty. Furthermore, multiple regression analyses based on individual trial activity showed that all three memory signals, i.e., recollection, familiarity, and novelty, make significant and independent contributions to recognition memory performance. Finally, functional dissociations among recollection, familiarity, and novelty were also found in posterior midline, left parietal cortex, and prefrontal cortex regions. This is the first study to reveal a triple dissociation within the MTL associated with distinct retrieval processes. This finding has direct implications for current memory models.

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