A unified framework for the functional organization of the medial temporal lobes and the phenomenology of episodic memory

Hippocampus ◽  
2010 ◽  
Vol 20 (11) ◽  
pp. 1263-1290 ◽  
Author(s):  
Charan Ranganath
Keyword(s):  
Episodic Memory ◽  
Functional Organization ◽  
Unified Framework ◽  
Medial Temporal Lobes ◽  
Temporal Lobes

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 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.

Recall, recognition, and the medial temporal lobes

1999 ◽  
Vol 22 (3) ◽  
pp. 455-456 ◽  
Author(s):  
Barbara J. Knowlton
Keyword(s):  
Episodic Memory ◽  
Current Evidence ◽  
Medial Temporal Lobes ◽  
Temporal Lobes

Aggleton & Brown predict that recognition and episodic recall depend on different brain systems and can thus be dissociated from one another. However, intact recall with impaired recognition has not yet been demonstrated if the same type of information is used in both tests. Current evidence suggests that processes underlying familiarity-based recognition are redundant with processes underlying episodic memory.

scholarly journals Preservation of episodic memory in semantic dementia: The importance of regions beyond the medial temporal lobes

2016 ◽  
Vol 81 ◽  
pp. 50-60 ◽  
Author(s):  
Muireann Irish ◽  
Steffie Bunk ◽  
Sicong Tu ◽  
Jody Kamminga ◽  
John R. Hodges ◽  
...  
Keyword(s):  
Episodic Memory ◽  
Semantic Dementia ◽  
Medial Temporal Lobes ◽  
Temporal Lobes

The reliability of fMRI activations in the medial temporal lobes in a verbal episodic memory task

NeuroImage ◽  
2005 ◽  
Vol 28 (1) ◽  
pp. 122-131 ◽  
Author(s):  
Kathrin Wagner ◽  
Lars Frings ◽  
Ansgar Quiske ◽  
Josef Unterrainer ◽  
Ralf Schwarzwald ◽  
...  
Keyword(s):  
Episodic Memory ◽  
Memory Task ◽  
Medial Temporal Lobes ◽  
Temporal Lobes ◽  
Verbal Episodic Memory

Evidence for a gradient within the medial temporal lobes for flexible retrieval under hierarchical task rules

Hippocampus ◽  
2021 ◽  
Author(s):  
Thackery I. Brown ◽  
Qiliang He ◽  
Irem Aselcioglu ◽  
Chantal E. Stern
Keyword(s):  
Medial Temporal Lobes ◽  
Temporal Lobes

Structural Changes in Thalamic Nuclei Across Prodromal and Clinical Alzheimer’s Disease

2021 ◽  
pp. 1-11
Author(s):  
Adam S. Bernstein ◽  
Steven Z. Rapcsak ◽  
Michael Hornberger ◽  
Manojkumar Saranathan ◽  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Large Scale ◽  
Structural Changes ◽  
Thalamic Nuclei ◽  
Medial Temporal Lobes ◽  
Cognitive Changes ◽  
Temporal Lobes ◽  
Medial Geniculate ◽  
Healthy Control

Background: Increasing evidence suggests that thalamic nuclei may atrophy in Alzheimer’s disease (AD). We hypothesized that there will be significant atrophy of limbic thalamic nuclei associated with declining memory and cognition across the AD continuum. Objective: The objective of this work was to characterize volume differences in thalamic nuclei in subjects with early and late mild cognitive impairment (MCI) as well as AD when compared to healthy control (HC) subjects using a novel MRI-based thalamic segmentation technique (THOMAS). Methods: MPRAGE data from the ADNI database were used in this study (n = 540). Healthy control (n = 125), early MCI (n = 212), late MCI (n = 114), and AD subjects (n = 89) were selected, and their MRI data were parcellated to determine the volumes of 11 thalamic nuclei for each subject. Volumes across the different clinical subgroups were compared using ANCOVA. Results: There were significant differences in thalamic nuclei volumes between HC, late MCI, and AD subjects. The anteroventral, mediodorsal, pulvinar, medial geniculate, and centromedian nuclei were significantly smaller in subjects with late MCI and AD when compared to HC subjects. Furthermore, the mediodorsal, pulvinar, and medial geniculate nuclei were significantly smaller in early MCI when compared to HC subjects. Conclusion: This work highlights nucleus specific atrophy within the thalamus in subjects with early and late MCI and AD. This is consistent with the hypothesis that memory and cognitive changes in AD are mediated by damage to a large-scale integrated neural network that extends beyond the medial temporal lobes.

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