The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Mieke Verfaellie - One of the best experts on this subject based on the ideXlab platform.
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personal Semantic Memory insights from neuropsychological research on amnesia
Neuropsychologia, 2014Co-Authors: Matthew D Grilli, Mieke VerfaellieAbstract:Abstract This paper provides insight into the cognitive and neural mechanisms of personal Semantic Memory, knowledge that is specific and unique to individuals, by reviewing neuropsychological research on stable amnesia secondary to medial temporal lobe damage. The results reveal that personal Semantic Memory does not depend on a unitary set of cognitive and neural mechanisms. Findings show that autobiographical fact knowledge reflects an experience-near type of personal Semantic Memory that relies on the medial temporal lobe for retrieval, albeit less so than personal episodic Memory. Additional evidence demonstrates that new autobiographical fact learning likely relies on the medial temporal lobe, but the extent to which remains unclear. Other findings show that retrieval of personal traits/roles and new learning of personal traits/roles and thoughts/beliefs are independent of the medial temporal lobe and thus may represent highly conceptual types of personal Semantic Memory that are stored in the neocortex.
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interdependence of episodic and Semantic Memory evidence from neuropsychology
Journal of The International Neuropsychological Society, 2010Co-Authors: Daniel L Greenberg, Mieke VerfaellieAbstract:Tulving's (1972) theory of Memory draws a distinction between general knowledge (Semantic Memory) and Memory for events (episodic Memory). Neuropsychological studies have generally examined each type of Memory in isolation, but theorists have long argued that these two forms of Memory are interdependent. Here we review several lines of neuropsychological research that have explored the interdependence of episodic and Semantic Memory. The studies show that these forms of Memory can affect each other both at encoding and at retrieval. We suggest that theories of Memory should be revised to account for all of the interdependencies between episodic and Semantic Memory; they should also incorporate forms of Memory that do not fit neatly into either category.
John R. Hodges - One of the best experts on this subject based on the ideXlab platform.
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The human perirhinal cortex and Semantic Memory
European Journal of Neuroscience, 2004Co-Authors: R. Rhys Davies, Kim S. Graham, John H. Xuereb, Guy B. Williams, John R. HodgesAbstract:Studies in macaque monkeys indicate that the perirhinal cortex in the temporal lobe participates in object Memory. This function may be analogous to aspects of human Semantic Memory (knowledge of objects, concepts, faces and words). To date, the status of perirhinal cortex has not specifically been investigated in patients with Semantic deficits as seen in Semantic dementia, the temporal lobe variant of frontotemporal dementia. High-resolution three-dimensional magnetic resonance imaging was performed in subjects with Semantic dementia and Alzheimer's disease (characterized in its early stages by selective episodic Memory impairment) and in healthy age-matched controls. Hippocampal, perirhinal, temporopolar and entorhinal cortex volumes were measured by outlining areas on successive scan slices according to recognized landmarks. The entorhinal and hippocampal regions were further subdivided into anterior and posterior parts. In keeping with the hypothesized contribution of the perirhinal cortex to Semantic Memory function, we found greater involvement of this region, together with the temporopolar and anterior entorhinal cortices, in Semantic dementia than in either Alzheimer's disease patients or control subjects. Performance on a range of Semantic tests also correlated with perirhinal volume. Bilateral reduction in hippocampal volume compared with controls was seen in Alzheimer's disease. In conclusion, atrophy of the human perirhinal cortex, and of directly connected areas, was associated with Semantic Memory impairment but not episodic Memory impairment, as predicted from the primate work.
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Insights from Semantic dementia on the relationship between episodic and Semantic Memory
Neuropsychologia, 2000Co-Authors: Kim S. Graham, Karalyn Patterson, Jon S. Simons, Katherine H. Pratt, John R. HodgesAbstract:An influential theory of long-term Memory, in which new episodic learning is dependent upon the integrity of Semantic Memory, predicts that a double dissociation between episodic and Semantic Memory is not possible in new learning. Contrary to this view, we found, in two separate experiments, that patients with impaired Semantic Memory showed relatively preserved performance on tests of recognition Memory if the stimuli were perceptually identical between learning and test. A significant effect of Semantic Memory was only seen when a perceptual manipulation was introduced in the episodic task. To account for these findings, we propose a revision to current models of long-term Memory, in which sensory/perceptual information and Semantic Memory work in concert to support new learning.
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Semantic Memory disorders.
Trends in Cognitive Sciences, 1997Co-Authors: John R. Hodges, Karalyn PattersonAbstract:Semantic Memory encompasses knowledge of objects, facts and words. A number of brain regions are probably involved, but the left infero-lateral temporal lobe appears to play a key role. The separability of Semantic Memory from episodic (or autobiographical) Memory is a focus of current debate. Impaired Semantic Memory is a common feature of Alzheimer's disease but is invariably overshadowed by a profound deficit in episodic Memory. In Semantic dementia, a rarer disorder associated with focal temporal-lobe atrophy, there is selective loss of Semantic Memory, characterized by preservation of superordinate knowledge of words, and objects, but loss of finer-grained information. This pattern can be interpreted as a degradation of features from a distributed network of Semantic representations. Following Herpes simplex encephalitis, patients sometimes show disproportionate loss of knowledge for natural kinds (e.g. animals) with relative preservation of knowledge about artefacts, this may reflect differential damage to neural systems critical for perceptual as opposed to functional features, perceptual properties being more salient in knowledge about natural kinds.
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A COMPARISON OF Semantic Memory IN VASCULAR DEMENTIA AND DEMENTIA OF ALZHEIMER'S TYPE
International Journal of Geriatric Psychiatry, 1997Co-Authors: Peter Bentham, Stephen Jones, John R. HodgesAbstract:Objective. To determine whether Semantic Memory is impaired in vascular dementia and to assess the utility of Semantic Memory measures in differentiating vascular dementia from dementia of Alzheimer's type (DAT). Design. Case-control study. Patients. Ten patients with Cambridge Mental Disorders in the Elderly (CAMDEX) diagnosis of ‘definite’ mild or moderate vascular dementia (mean age 77) were individually matched with 10 patients with a CAMDEX diagnosis of ‘definite’ DAT on the basis of age, education, sex, premorbid IQ (as measured by the National Adult Reading Test) and performance on the Cambridge Cognitive Examination (CAMCOG). In addition, 10 age, sex and education matched volunteer or relative controls were assessed. Outcome measures. A detailed Semantic Memory test battery consisting of five subtests: category fluency, picture naming, picture sorting, word–picture matching and generation of verbal definitions. Results. Compared to normal controls, both patient groups were impaired on all subtests of the Semantic battery with the exception of the word–picture matching test. No differences were found between the vascular dementia and DAT groups on any of the measures. Conclusions. Impairment of Semantic Memory is a feature of both vascular dementia and DAT. Tests of Semantic Memory appear, therefore, of little value in differentiating between these two major causes of dementia. Further work is required to determine whether the nature of the processing deficit is the same in these conditions. © 1997 John Wiley & Sons, Ltd.
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Semantic Memory is impaired in schizophrenia.
Biological Psychiatry, 1996Co-Authors: A. Paula Mckay, Peter J. Mckenna, Peter Bentham, Ann M. Mortimer, Alison Holbery, John R. HodgesAbstract:Memory is emerging as a key area of neuropsychological deficit in schizophrenia, with evidence suggesting that the impairment is restricted to long-term Memory. Semantic Memory, the component of long-term Memory containing stored representations of the meanings of words and knowledge about the world, was examined in 46 schizophrenic patients and 40 normal controls using a recently devised battery of tests. Evidence of Semantic Memory impairment was found which was wide ranging and substantial; in some cases it approached the levels seen in a group of 22 patients with mild-to-moderate Alzheimer's disease. Both group analysis and a more detailed examination of two single cases suggested that Semantic Memory impairment represents a disproportionate and possibly specific neuropsychological deficit in schizophrenia.
Matthew D Grilli - One of the best experts on this subject based on the ideXlab platform.
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personal Semantic Memory insights from neuropsychological research on amnesia
Neuropsychologia, 2014Co-Authors: Matthew D Grilli, Mieke VerfaellieAbstract:Abstract This paper provides insight into the cognitive and neural mechanisms of personal Semantic Memory, knowledge that is specific and unique to individuals, by reviewing neuropsychological research on stable amnesia secondary to medial temporal lobe damage. The results reveal that personal Semantic Memory does not depend on a unitary set of cognitive and neural mechanisms. Findings show that autobiographical fact knowledge reflects an experience-near type of personal Semantic Memory that relies on the medial temporal lobe for retrieval, albeit less so than personal episodic Memory. Additional evidence demonstrates that new autobiographical fact learning likely relies on the medial temporal lobe, but the extent to which remains unclear. Other findings show that retrieval of personal traits/roles and new learning of personal traits/roles and thoughts/beliefs are independent of the medial temporal lobe and thus may represent highly conceptual types of personal Semantic Memory that are stored in the neocortex.
Howard Chertkow - One of the best experts on this subject based on the ideXlab platform.
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Semantic Memory.
Current neurology and neuroscience reports, 2002Co-Authors: Daniel Saumier, Howard ChertkowAbstract:Our concepts about objects, states, and events are stored in a cognitive structure termed Semantic Memory. There are several types of neurologic disorders that may cause impairments of Semantic Memory. Clinical evaluations of these impairments are complex, because Semantic Memory is linked to other cognitive systems that, when damaged, may produce related syndromes or difficulties. In an attempt to gain further understanding of these breakdown patterns, we review data from both neuropsychologic and brain activity research that have been concerned with how object concepts are represented and localized in the brain. Although these data have spawned varying and controversial views regarding the content and organization of Semantic knowledge, converging evidence suggests that Semantic Memory is mainly localized in the posterior region of the left temporal lobe, and that particular categories of knowledge may be represented in different but overlapping regions within this area.
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Semantic Memory loss in dementia of Alzheimer's type. What do various measures measure?
Brain, 1990Co-Authors: Howard Chertkow, Daniel BubAbstract:This paper examines three methodological issues concerning the measurement of Semantic Memory impairment in brain-damaged patients. Ten carefully selected patients with dementia of Alzheimer's type (DAT) and anomia were studied. A battery of perceptual tests and direct tests of Semantic Memory led to the conclusion that these patients represented a homogeneous group having a prominent deterioration of their Semantic Memory store without visual perceptual deficits. The first issue addressed in this patient group was whether verbal fluency impairment accurately reflected the loss of Semantic Memory. It was found that verbal fluency (generation of Semantic category lists) was impaired due to two major constraints: deterioration of Semantic Memory store, and variable difficulties in Semantic search. Verbal fluency, therefore, reflects Semantic Memory loss to some degree, but is not a direct test of Semantic Memory store in DAT. The second issue was whether Semantic Memory impairment in our patients conformed to the ‘Semantic storage disorder’ syndrome hypothesized by Shallice (1987). It was shown that, consistent with this hypothesis, the patients demonstrated co-occurrence of consistency of errors, loss of Semantic cueing, and preserved superordinate knowledge with loss of detailed knowledge of concept items. The third issue was whether Semantic cueing and Semantic priming, are altered in a similar manner in DAT. It demonstrated that Semantic cueing and Semantic priming, using the same words whose concepts were degraded in Semantic Memory, yielded an entirely different pattern of results. Cueing and priming therefore may not be used interchangeably in the study of Semantic loss after brain damage.
James L Mcclelland - One of the best experts on this subject based on the ideXlab platform.
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a computational model of Semantic Memory impairment modality specificity and emergent category specificity
Journal of Experimental Psychology: General, 1991Co-Authors: Martha J Farah, James L McclellandAbstract:It is demonstrated how a modality-specific Semantic Memory system can account for categoryspecific impairments after brain damage. In Experiment I, the hypothesis that visual and functional knowledge play different roles in the representation of living things and nonliving things is tested and confirmed. A parallel distributed processing model of Semantic Memory in which knowledge is subdivided by modality into visual and functional components is described. In Experiment 2, the model is lesioned, and it is confirmed that damage to visual Semantics primarily impairs knowledge of living things, and damage to functional Semantics primarily impairs knowledge of nonliving things. In Experiment 3, it is demonstrated that the model accounts naturally for a finding that had appeared problematic for a modality-specific architecture, namely, impaired retrieval of functional knowledge about living things. Finally, in Experiment 4, it is shown how the model can account for a recent observation of impaired knowledge of living things only when knowledge is probed verbally. How is Semantic Memory organized? Two general answers to this question have been proposed. One is that Semantic Memory is organized by taxonomic category, such that different parts of the system represent knowledge about objects from different categories. Alternatively, Semantic Memory could be subdivided by modality of knowledge, such that one component is responsible for visual information about objects, another for auditory information , and so on. Patients with selective losses of knowledge after brain damage appear to provide a direct source of evidence on the organization of Semantic Memory. Unfortunately, this evidence yields conflicting answers. In most cases , the losses appear to be tied to specific modalities , resulting in impaired recognition of objects in just one modality (e. , visual or auditory agnosia) or in impaired manipulation of objects with specific uses, despite intact recognition of them (apraxia; e. g., a key might be pulled, rather than turned). These observations are consistent with recent neurophysiological data showing that most cortical neurons are modality-specific, even in regions that were traditionally viewed as supramodal association areas (e. , Sereno & Allman, 1991). In some cases, however, brain damage seems to cause category-specific losses of knowledge, which cut across different modalities. Specifically, there are patients who seem to have lost their knowledge of living things, and others who seem to have lost their knowledge of nonliving things. These observations suggest that the architecture of Semantic Memory incorporates at least
