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IC‐P‐161: Semantic memory impairment in Alzheimer's disease and frontotemporal dementia is associated with semantic network degradation
Author(s) -
DomotoReilly Kimiko,
Sapolsky Daisy,
Brickhouse Michael,
Hollenbeck Mark,
Dickerson Brad
Publication year - 2011
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2011.05.175
Subject(s) - semantic dementia , semantic memory , psychology , atrophy , frontotemporal dementia , temporal lobe , episodic memory , dementia , semantics (computer science) , cognition , neuroscience , cognitive psychology , disease , computer science , medicine , pathology , epilepsy , programming language
Background: Semantic memory deficits in early AD are typically subtle, and overshadowed by other cognitive impairments such as problems with episodic memory. FTD, in contrast, can sometimes cause early, prominent semantic impairment. Ongoing debate regarding the localization of semantic memory has focused on whether there is a distributed set of brain regions with convergence zones in association cortices, or whether the anterior temporal lobes form a “hub” for centralizing conceptual processing. We performed a series of analyses to address this issue. First, we examined ADNI data to determine the correlation between regional cortical atrophy and degree of semantic impairment in early AD. Our group has previously demonstrated that AD affects a “signature set” of cortical regions, overlapping with the default mode network. We hypothesized that, if semantic memory is subserved primarily by a distributed set of brain regions, the degree of semantic impairment in AD would correlate with the degree of atrophy distributed throughout this large-scale network. In contrast, if access to semanticmemory requires a temporal pole hub, patients with greater semantic impairment would have greater atrophy in a pattern more consistent with a temporopolar network. Second, we analyzed FTD patients to identify brain regions associated with prominent semantic impairment. Methods: We extracted Boston Naming Test data from mild AD patients in ADNI. Cortical thickness analysis was performed, identifying areas in which cortical thinning was correlated with naming impairment, controlling for age, sex, education, and MMSE score. We performed a similar analysis of FTD patients (all subtypes).We then compared the thinningmaps associated with semantic impairment between the two diseases. Results: Naming impairment correlated strongly with left-lateralized anterior and lateral temporal cortical thinning, and not with thinning in the overall AD signature. This pattern was very similar in FTD.Conclusions:The basis for naming deficits in early AD appears to be neurodegeneration of temporal regions associated with lexico-semantic abilities. Semantic impairment in FTD follows a similar pattern: atrophy prominently affecting the ventral language network, with relative dorsal sparing. These findings provide further support that neurodegenerative diseases may target specific cognitive-behavioral brain networks, but demonstrate that distinct diseases may affect a single network. P4-094 A SPECIFIC RELATIONSHIP BETWEEN HIPPOCAMPAL CA1 SUBFIELD ATROPHYAND EPISODIC MEMORY ENCODING IN AMNESTIC MILD COGNITIVE IMPAIRMENT Marine Fouquet, B eatrice Desgranges, Renaud La Joie, Denis Rivi ere, Brigitte Landeau, Florence M ezenge, Vincent de La Sayette, Fausto Viader, Jean-François Mangin, Jean-Claude Baron, Francis Eustache, Ga€el Ch etelat, INSERM-EPHE-UCBN U923, Caen, France; CEA LNAO, Gif-sur-Yvette, France; University of Cambridge, Cambridge, United Kingdom.