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Larry R Squire - One of the best experts on this subject based on the ideXlab platform.
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Eye movements support the link between conscious memory and Medial Temporal Lobe function.
Proceedings of the National Academy of Sciences of the United States of America, 2018Co-Authors: Zhisen J. Urgolites, Christine N. Smith, Larry R SquireAbstract:When individuals select the recently studied (and familiar) item in a multiple-choice memory test, they direct a greater proportion of viewing time toward the to-be-selected item when their choice is correct than when their choice is incorrect. Thus, for both correct and incorrect choices, individuals indicate that the chosen item is old, but viewing time nevertheless distinguishes between old and new items. What kind of memory supports this preferential viewing effect? We recorded eye movements while participants made three-alternative, forced-choice recognition memory judgments for scenes. In experiment 1 (n = 30), the magnitude of the preferential viewing effect was strongly correlated with measures of conscious, declarative memory: recognition accuracy as well as the difference in confidence ratings and in response times for correct and incorrect choices. In four analyses that minimized the contribution of declarative memory in order to detect a possible contribution from other processes, the preferential viewing effect was absent. In experiment 2, five memory-impaired patients with Medial Temporal Lobe lesions exhibited a diminished preferential viewing effect. These patients also exhibited poor recognition accuracy and reduced differences in confidence ratings and response times for correct and incorrect choices. We propose that the preferential viewing effect is a phenomenon of conscious, declarative memory and is dependent on the Medial Temporal Lobe. The findings support the link between Medial Temporal Lobe function and declarative memory. When the effects of experience depend on the Medial Temporal Lobe, the effects reflect conscious memory.
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Intact working memory for relational information after Medial Temporal Lobe damage.
The Journal of Neuroscience, 2010Co-Authors: Annette Jeneson, Kristin N. Mauldin, Larry R SquireAbstract:Working memory has traditionally been viewed as independent of the hippocampus and related Medial Temporal Lobe structures. Yet memory-impaired patients with Medial Temporal Lobe damage are sometimes impaired at remembering relational information (e.g., an object and its location) across delays as short as a few seconds. This observation has raised the possibility that Medial Temporal Lobe structures are sometimes critical for maintaining relational information, regardless of whether the task depends on working or long-term memory. An alternative possibility is that these structures are critical for maintaining relational information only when the task exceeds working memory capacity and depends instead on long-term memory. To test these ideas, we drew on a method used previously in a classic study of digit span in patient HM that distinguished immediate memory from long-term memory. In two experiments, we assessed the ability of four patients with Medial Temporal Lobe lesions to maintain varying numbers of object-location associations across a 1 s retention interval. In both experiments, the patients exhibited a similar pattern of performance. They performed similarly to controls when only a small number of object-location associations needed to be maintained, and they exhibited an abrupt discontinuity in performance with larger set sizes. This pattern of results supports the idea that maintenance of relational information in working memory is intact after damage to the hippocampus and related Medial Temporal Lobe structures and that damage to these structures impairs performance only when the task depends on long-term memory.
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An animal model of recognition memory and Medial Temporal Lobe amnesia: History and current issues
Neuropsychologia, 2010Co-Authors: Robert E. Clark, Larry R SquireAbstract:The Medial Temporal Lobe includes a system of anatomically connected structures that are essential for declarative memory (conscious memory for facts and events). A prominent form of declarative memory is recognition memory (the ability to identify a recently encountered item as familiar). Recognition memory has been frequently assessed in humans and in the experimental animal. This article traces the successful development of an animal model of human Medial Temporal Lobe amnesia, which eventually identified the structures in the Medial Temporal Lobe important for memory. Attention is given to two prominent behavioral paradigms (delayed nonmatching to sample and tests of spontaneous novelty preference).
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Chapter 3.2 The Medial Temporal Lobe: visual perception and recognition memory
Handbook of Behavioral Neuroscience, 2008Co-Authors: Yael Shrager, Larry R SquireAbstract:Abstract The hippocampus and adjacent Medial Temporal Lobe structures support declarative memory. This chapter addresses two issues of recent interest concerning the function of Medial Temporal Lobe structures. The first issue concerns the proposal that the structures of the Medial Temporal Lobe support visual perception in addition to memory, which challenges the long-standing idea that the ability to acquire new memories is separable from other cognitive and perceptual functions. We describe a series of rigorous visual-perceptual experiments involving patients with damage to the Medial Temporal Lobe that revealed no evidence of visual-perceptual deficits. We conclude that the Medial Temporal Lobe is not necessary for visual perception. The second issue concerns the idea that the hippocampus might support recollection, whereas the adjacent Medial Temporal Lobe structures support familiarity. We describe a study involving patients with hippocampal lesions that found memory impairment in both recollection and familiarity, with no special impairment in recollection. We also describe a study with epileptic patients from a different laboratory that found neuronal responses associated with familiarity, even in the absence of recollection. We conclude that the hippocampus mediates both recollection and familiarity.
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New semantic learning in patients with large Medial Temporal Lobe lesions.
Hippocampus, 2008Co-Authors: Peter J. Bayley, Randall C. O'reilly, Tim Curran, Larry R SquireAbstract:Two patients with large lesions of the Medial Temporal Lobe were given four tests of semantic knowledge that could only have been acquired after the onset of their amnesia. In contrast to previous studies of postmorbid semantic learning, correct answers could be based on a simple, nonspecific sense of familiarity about single words, faces, or objects. According to recent computational models (for example, Norman and O'Reilly (2003) Psychol Rev 110:611-646), this character- istic should be optimal for detecting the kind of semantic learning that might be supported directly by the neocortex. Both patients exhibited some capacity for new learning, albeit at a level substantially below control performances. Notably, the correct answers appeared to reflect declarative memory. It was not the case that the correct answers simply popped out in some automatic way in the absence of any additional knowledge about the items. Rather, the few correct choices made by the patients tended to be accompanied by additional information about the chosen items, and the available knowledge appeared to be similar qualitatively to the kind of factual knowledge that healthy individuals gradually acquire over the years. The results are consistent with the idea that neocortical structures outside the Medial Temporal Lobe are able to support some semantic learning, albeit to a very limited extent. Alternatively, the small amount of learning detected in the present study could depend on tissue within the posterior Medial Temporal Lobe that remains intact in both patients. V C 2008 Wiley-Liss, Inc.
M. G. Baxter - One of the best experts on this subject based on the ideXlab platform.
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Visual perception and memory systems: From cortex to Medial Temporal Lobe
Cellular and Molecular Life Sciences, 2011Co-Authors: Zafar U. Khan, Elisa Martín-montañez, M. G. BaxterAbstract:Visual perception and memory are the most important components of vision processing in the brain. It was thought that the perceptual aspect of a visual stimulus occurs in visual cortical areas and that this serves as the substrate for the formation of visual memory in a distinct part of the brain called the Medial Temporal Lobe. However, current evidence indicates that there is no functional separation of areas. Entire visual cortical pathways and connecting Medial Temporal Lobe are important for both perception and visual memory. Though some aspects of this view are debated, evidence from both sides will be explored here. In this review, we will discuss the anatomical and functional architecture of the entire system and the implications of these structures in visual perception and memory.
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Involvement of Medial Temporal Lobe structures in memory and perception.
Neuron, 2009Co-Authors: M. G. BaxterAbstract:Beginning approximately a decade and a half ago, it was suggested that some structures that are considered to be part of the "Medial Temporal Lobe memory system" could play a role in perception as well. The implications of this view, interpreted broadly, are that Medial Temporal Lobe structures may be understood as an extension of the ventral visual stream and that their functions cannot be described exclusively in terms of memory. Considerable evidence now supports the view that Medial Temporal Lobe structures are involved in nonmnemonic aspects of cognition, such as perception. This discovery allows for a fuller understanding of the involvement of these structures in mental phenomena than does a purely mnemonic account of their function. See the related review by Suzuki, "Perception and the Medial Temporal Lobe: Evaluating the Current Evidence," in this issue of Neuron.
Philip Scheltens - One of the best experts on this subject based on the ideXlab platform.
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Medial Temporal Lobe atrophy and memory dysfunction as predictors for dementia in subjects with mild cognitive impairment
Journal of Neurology, 2017Co-Authors: Pieter Jelle Visser, Frans R.j. Verhey, Jelle Jolles, Philip Scheltens, Ben Schmand, Leonore J. Launer, Cees JonkerAbstract:To determine whether the Medial Temporal Lobe is atrophic in subjects with mild cognitive impairment, and whether atrophy of this structure is a better predictor of dementia than memory dysfunction. Forty-five noninstitutionalized subjects aged 65–85 years were randomly selected from a population based study to obtain a sample with Alzheimer’s disease (AD; n = 7), and a clinically nondemented sample (n = 38). Twenty of the latter subjects displayed some cognitive impairment and fulfilled CAMDEX criteria for “minimal dementia.” Coronal T1-weighted magnetic resonance imaging was used to visualize the Medial Temporal Lobe. The volume of the parahippocampal gyrus and hippocampus was measured, and Medial Temporal Lobe atrophy was assessed qualitatively. The memory subscore from the CAMCOG was used as a measure of memory functioning. The follow-up period was 3 years. Nine subjects who were diagnosed as being minimally demented at baseline met the criteria for AD during follow-up. At baseline the volume of the parahippocampal gyrus of these subjects was smaller than that of the other subjects with minimal dementia. The memory score was the best predictor of clinical outcome. All Medial Temporal Lobe measures increased the accuracy of prediction compared with only the memory score, by reducing the number of false-negative classifications of dementia. Severe Medial Temporal Lobe atrophy is present even in some subjects with mild cognitive impairment and is an indicator of subsequent AD. The absence of Medial Temporal Lobe atrophy, however, does not exclude the development of dementia. In the majority of subjects memory impairment was a better predictor of dementia than atrophy of the Medial Temporal Lobe. The combination of the two increased predictive accuracy. Nondemented subjects with severe atrophy of the Medial Temporal Lobe could be enrolled in drug trials aimed at slowing the progression of AD.
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visual rating and volumetry of the Medial Temporal Lobe on magnetic resonance imaging in dementia a comparative study
Journal of Neurology Neurosurgery and Psychiatry, 2000Co-Authors: Lars-olof Wahlund, Per Julin, Svenerik Johansson, Philip ScheltensAbstract:OBJECTIVES It has been shown that atrophy of Medial Temporal Lobe structures such as the hippocampus and entorhinal cortex shown on MRI may distinguish patients with Alzheimer9s disease from healthy controls. However, the diagnostic value of visual inspection and volumetry of Medial Temporal Lobe atrophy (MTA) on MRI in a clinical setting is insufficiently known. METHODS Medial Temporal Lobe atrophy in 143 patients was visually rated from hard copies, using a 0–4 rating scale and a comparison was made with the volumes (cm 3 ) of the Medial Temporal Lobe as estimated with volumetry, using a stereological method. All patients were recruited in an unselected way in a clinical setting in the centre for memory impairments at the Huddinge University Hospital. Patients with Alzheimer9s disease (n=41), patients with other dementias (vascular dementia, frontoTemporal dementia, and unspecified dementia; n=36) as well as non-demented subjects (n=66) were included. Medial Temporal atrophy and volumetry were evaluated as a diagnostic tool by performing logistic regression analysis including age, sex, and mini mental state examination (MMSE) score and calculating the sensitivity and specificity and percentage correct classification. RESULTS Visual and volumetric analysis yielded statistically significant differences between patients with Alzheimer9s disease and non-demented subjects, as well as between those with other dementias and non-demented subjects. Combining MMSE scores and visually rated MTA ratings yielded a sensitivity of 95% for Alzheimer9s disease, 85% for other dementias. Non-demented subjects were identified with a specificity of 96%. Volumetry did not have an added value over the MMSE score alone. CONCLUSIONS Visual rating of MTA is a clinically useful method for differentiating Alzheimer9s disease from controls and is both quicker and more accurate than volumetry.
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Visual assessment of Medial Temporal Lobe atrophy in demented and healthy control subjects: correlation with volumetry
Psychiatry Research-neuroimaging, 1999Co-Authors: Lars-olof Wahlund, Per Julin, Johan Lindqvist, Philip ScheltensAbstract:The present study evaluated the validity of visual rating of Medial Temporal Lobe atrophy on coronal magnetic resonance imaging scans in a population of demented and non-demented individuals. Medial Temporal Lobe atrophy in 194 subjects was visually rated from hard copies, using a 0-4 rating scale, and a comparison was made with the absolute volumes (ccm) of the Medial Temporal Lobe as estimated with volumetry, using a stereological method. We found a highly significant correlation between the estimated and stereologically measured volumes. There was a 10-fold difference in time spent on rating Medial Temporal Lobe atrophy (1-2 min) vs. time spent calculating the Medial Temporal Lobe volume (10-12 min) on a single subject. The diagnostic accuracy of both methods showed that visual rating was more efficient than volumetry in differentiating Alzheimer's disease from control subjects, We conclude that visual rating is a reliable and fast method to estimate Medial Temporal Lobe atrophy in demented subjects in a clinical setting.
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Parametric fMRI analysis of visual encoding in the human Medial Temporal Lobe
Hippocampus, 1999Co-Authors: Serge A.r.b. Rombouts, Philip Scheltens, Frederik Barkhof, Willem C.m. Machielsen, Frank G. C. Hoogenraad, Dick J. Veltman, Jaap Valk, Menno P. WitterAbstract:A number of functional brain imaging studies indicate that the Medial Temporal Lobe system is crucially involved in encoding new information into memory. However, most studies were based on differences in brain activity between encoding of familiar vs. novel stimuli. To further study the underlying cognitive processes, we applied a parametric design of encoding. Seven healthy subjects were instructed to encode complex color pictures into memory. Stimuli were presented in a parametric fashion at different rates, thus representing different loads of encoding. Functional magnetic resonance imaging (fMRI) was used to assess changes in brain activation. To determine the number of pictures successfully stored into memory, recognition scores were determined afterwards. During encoding, brain activation occurred in the Medial Temporal Lobe, comparable to the results obtained by others. Increasing the encoding load resulted in an increase in the number of successfully stored items. This was reflected in a significant increase in brain activation in the left lingual gyrus, in the left and right parahippocampal gyrus, and in the right inferior frontal gyrus. This study shows that fMRI can detect changes in brain activation during variation of one aspect of higher cognitive tasks. Further, it strongly supports the notion that the human Medial Temporal Lobe is involved in encoding novel visual information into memory.
Peter J. Bayley - One of the best experts on this subject based on the ideXlab platform.
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New semantic learning in patients with large Medial Temporal Lobe lesions.
Hippocampus, 2008Co-Authors: Peter J. Bayley, Randall C. O'reilly, Tim Curran, Larry R SquireAbstract:Two patients with large lesions of the Medial Temporal Lobe were given four tests of semantic knowledge that could only have been acquired after the onset of their amnesia. In contrast to previous studies of postmorbid semantic learning, correct answers could be based on a simple, nonspecific sense of familiarity about single words, faces, or objects. According to recent computational models (for example, Norman and O'Reilly (2003) Psychol Rev 110:611-646), this character- istic should be optimal for detecting the kind of semantic learning that might be supported directly by the neocortex. Both patients exhibited some capacity for new learning, albeit at a level substantially below control performances. Notably, the correct answers appeared to reflect declarative memory. It was not the case that the correct answers simply popped out in some automatic way in the absence of any additional knowledge about the items. Rather, the few correct choices made by the patients tended to be accompanied by additional information about the chosen items, and the available knowledge appeared to be similar qualitatively to the kind of factual knowledge that healthy individuals gradually acquire over the years. The results are consistent with the idea that neocortical structures outside the Medial Temporal Lobe are able to support some semantic learning, albeit to a very limited extent. Alternatively, the small amount of learning detected in the present study could depend on tissue within the posterior Medial Temporal Lobe that remains intact in both patients. V C 2008 Wiley-Liss, Inc.
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Detailed recollection of remote autobiographical memory after damage to the Medial Temporal Lobe
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: C. Brock Kirwan, Peter J. Bayley, Veronica Galvan, Larry R SquireAbstract:Previous findings of intact remote autobiographical memory in patients with Medial Temporal Lobe damage have been questioned on the grounds that the narrative recollections were impoverished and fact-like and that the methods were not sufficiently sensitive to detect an impairment. We adopted a newer method, the Autobiographical Interview [Levine B, Svoboda E, Hay JF, Winocur G, Moscovitch M (2002) Psychol Aging 17:677–689], which uses extensive probing to elicit an average of 50 or more details per memory (in contrast to the ≈20 details per memory elicited with previous methods). We found that autobiographical recollection was impaired in patients with Medial Temporal Lobe damage when memories were drawn from the recent past but fully intact when memories were drawn from the remote past. Impaired remote autobiographical memory, which has sometimes been reported with this and other tests, is likely caused by significant damage outside the Medial Temporal Lobe.
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The Fate of Old Memories after Medial Temporal Lobe Damage
The Journal of Neuroscience, 2006Co-Authors: Peter J. Bayley, Ramona O. Hopkins, Larry R SquireAbstract:Damage to the hippocampal region and related Medial Temporal Lobe structures (perirhinal, entorhinal, and parahippocampal cortices) impairs new learning (anterograde amnesia) as well as memory for information that was acquired before the damage occurred (retrograde amnesia). We assessed retrograde amnesia with the Autobiographical Memory Interview (AMI) and with a news events test in six patients with damage limited primarily to the hippocampal region (H group) and two patients with large Medial Temporal Lobe lesions (MTL group). On the news event test, the H group exhibited Temporally limited retrograde amnesia covering ∼5 years. On the same test, the MTL group exhibited an extensive retrograde amnesia covering decades. Nevertheless, performance was relatively spared for very remote time periods. On the AMI, all patients had intact remote autobiographical memory. Because our patients with hippocampal lesions, as well as our patients with large MTL lesions, performed normally on the AMI, patients who perform poorly on the same test presumably have damage beyond the hippocampus and related structures in the Medial Temporal Lobe. The findings emphasize the difference in the extent of retrograde amnesia associated with hippocampal lesions and large MTL lesions.
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The Medial Temporal Lobe and declarative memory
International Congress Series, 2003Co-Authors: Peter J. Bayley, Larry R SquireAbstract:Abstract The hippocampus is part of a system of anatomically related structures in the Medial Temporal Lobe that supports the capacity for conscious recollection (declarative memory). In three studies, we investigated memory functions in amnesic patients with bilateral damage limited primarily to the hippocampal region and in other patients with larger lesions of the Medial Temporal Lobe. The results support three conclusions about the neurological organization of human memory. First, to a limited degree, nondeclarative memory can substitute for declarative memory, but what is learned and stored in memory is substantially different depending on which memory system is used. Second, damage limited primarily to the hippocampal region impairs the learning of new facts (semantic memory), just as such damage impairs the learning of new events (episodic memory). Remote memory for factual knowledge is spared. Third, damage to the Medial Temporal Lobe spares remote memory for autobiographical events (episodic memory).
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successful recollection of remote autobiographical memories by amnesic patients with Medial Temporal Lobe lesions
Neuron, 2003Co-Authors: Peter J. Bayley, Ramona O. Hopkins, Larry R SquireAbstract:Abstract Current views about the organization of human memory make strikingly different predictions about the integrity of remote autobiographical memory following damage to the Medial Temporal Lobe. We have carried out a detailed analysis of narrative content in memory-impaired patients for whom neuropsychological and neuroanatomical information is available. All eight patients were able to recall detailed memories from their early lives. The recollections of the patients and the recollections of 25 matched controls contained the same number of details (±5%) and were also similar by several other measures. The results support the view that autobiographical memories eventually become independent of the Medial Temporal Lobe as time passes after learning. A number of other considerations suggest that the neocortex ultimately supports the capacity for recollecting remote autobiographical memory.
Anthony D. Wagner - One of the best experts on this subject based on the ideXlab platform.
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The Medial Temporal Lobe and Episodic Memory
Brain Mapping, 2015Co-Authors: Karen F. Larocque, Anthony D. WagnerAbstract:Memories for the events of one's personal past take multiple forms that are differentially enabled by distinct computations performed by the Medial Temporal Lobe (MTL). MTL cortex is posited to establish similar representations of similar events, enabling later recognition of single event attributes; the hippocampus is posited to establish distinct representations of similar events, enabling later memory for ensembles of co-occurring event attributes. These MTL contributions to episodic memory are situated within broader large-scale network interactions, including interactions with regions in the lateral prefrontal and lateral parietal cortices.
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imaging the human Medial Temporal Lobe with high resolution fmri
Neuron, 2010Co-Authors: Valerie A Carr, Jesse Rissman, Anthony D. WagnerAbstract:High-resolution functional MRI (hr-fMRI) affords unique leverage on the functional properties of human Medial Temporal Lobe (MTL) substructures. We review initial hr-fMRI efforts to delineate (1) encoding and retrieval processes within the hippocampal circuit, (2) hippocampal subfield contributions to pattern separation and pattern completion, and (3) the representational capabilities of distinct MTL subregions. Extant data reveal functional heterogeneity within human MTL and highlight the promise of hr-fMRI for bridging human, animal, and computational approaches to understanding MTL function.
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The Medial Temporal Lobe and memory
Neurobiology of Learning and Memory, 2007Co-Authors: Alison R. Preston, Anthony D. WagnerAbstract:Publisher Summary This chapter focuses on the role of Medial Temporal Lobe (MTL) structures—the hippocampus and surrounding parahippocampal, perirhinal, and entorhinal cortices—in memory processing and representation.. Particularly, bilateral damage to the MTL leads to impairments in declarative memory, long-term memory for general facts (semantic memory) and specific events (episodic memory). The MTL circuit is central to declarative memory, including the encoding, consolidation, and retrieval of episodic memories. The chapter focuses on the role of the MTL in episodic memory, first considering the relevant aspects of MTL anatomy and then considering neuropsychological and neuroimaging data in humans to understand the role of MTL in supporting memory for events. The chapter also illustrates neuropsychological and neuroimaging studies of human MTL that provides advanced understanding of the working of MTL in building memories of our daily experiences and subsequently, the retrieval of these memories to inform future goal-directed behavior.
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Multiple routes to memory: Distinct Medial Temporal Lobe processes build item and source memories
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Lila Davachi, Jason P. Mitchell, Anthony D. WagnerAbstract:A central function of memory is to permit an organism to distinguish between stimuli that have been previously encountered and those that are novel. Although the Medial Temporal Lobe (which includes the hippocampus and surrounding perirhinal, parahippocampal, and entorhinal cortices) is known to be crucial for recognition memory, controversy remains regarding how the specific subregions within the Medial Temporal Lobe contribute to recognition. We used event-related functional MRI to examine the relation between activation in distinct Medial Temporal Lobe subregions during memory formation and the ability (i) to later recognize an item as previously encountered (item recognition) and (ii) to later recollect specific contextual details about the prior encounter (source recollection). Encoding activation in hippocampus and in posterior parahippocampal cortex predicted later source recollection, but was uncorrelated with item recognition. In contrast, encoding activation in perirhinal cortex predicted later item recognition, but not subsequent source recollection. These outcomes suggest that the subregions within the Medial Temporal Lobe subserve distinct, but complementary, learning mechanisms.