Neural correlates of lexical-semantic memory: A voxel-based morphometry study in mild AD, aMCI and normal aging

Abstract

Neuroanatomical correlations of naming and lexical-semantic memory are not yet fully understood. The most influential approaches share the view that semantic representations reflect the manner in which information has been acquired through perception and action, and that each brain area processes different modalities of semantic representations. Despite these anatomical differences in semantic processing, generalization across different features that have similar semantic significance is one of the main characteristics of human cognition.MethodsWe evaluated the brain regions related to naming, and to the semantic generalization, of visually presented drawings of objects from the Boston Naming Test (BNT), which comprises different categories, such as animals, vegetables, tools, food, and furniture. In order to create a model of lesion method, a sample of 48 subjects presenting with a continuous decline both in cognitive functions, including naming skills, and in grey matter density (GMD) was compared to normal young adults with normal aging, amnestic mild cognitive impairment (aMCI) and mild Alzheimer’s disease (AD). Semantic errors on the BNT, as well as naming performance, were correlated with whole brain GMD as measured by voxel-based morphometry (VBM).ResultsThe areas most strongly related to naming and to semantic errors were the medial temporal structures, thalami, superior and inferior temporal gyri, especially their anterior parts, as well as prefrontal cortices (inferior and superior frontal gyri).ConclusionThe possible role of each of these areas in the lexical-semantic networks was discussed, along with their contribution to the models of semantic memory organization.

Functional changes in the cortical semantic network in amnestic mild cognitive impairment.

“…In contrast, semantic impairment represents one of the earliest features of cognitive decline in neurodegenerative diseases such as Alzheimer’s disease (AD; Adlam, Bozeat, Arnold, Watson, & Hodges, 2006; Amieva et al, 2008; Duong, Whitehead, Hanratty, & Chertkow, 2006; Joubert et al, 2010; Joubert et al, 2008; Libon et al, 2013; Wilson, Leurgans, Boyle, & Bennett, 2011). Studies on amnestic Mild cognitive impairment (aMCI), a condition considered by many authors to reflect a transitional stage between healthy aging and AD, have shown that although episodic memory deficits characterize this condition, aMCI patients also have deficits in SM (Adlam et al, 2006; Ahmed, Arnold, Thompson, Graham, & Hodges, 2008; Ally, 2012; Balthazar et al, 2011; Barbeau et al, 2012; Brambati, Peters, Belleville, & Joubert, 2012; Carter et al, 2012; Dudas, Clague, Thompson, Graham, & Hodges, 2005; Estévez-González et al, 2004; Joubert et al, 2010; Kirchberg et al, 2012; van der Meulen et al, 2012; Verma & Howard, 2012; Vogel, Gade, Stokholm, & Waldemar, 2005). Among the various types of knowledge investigated, knowledge of famous persons appears particularly prone to conceptual breakdown in this condition (Estévez-González et al, 2004; Joubert et al, 2008, 2010; Vogel et al, 2005).…”

fMRI Investigation of Semantic Lexical Processing in Healthy Control and Alzheimer’s Disease Subjects Using Naming Task: A Preliminary Study

“…While episodic memory loss is the most common syndrome in AD, language impairment is a common problem and an early sign of AD; naming and fluency deficits are particularly prevalent [11][12][13][14][15]. In the early stage of AD, word retrieval, and semantic-and episodic-memory impairment have been identified [16].…”

“…Semantic memory is critical for investigation since it is related to general facts and knowledge, and could affect the daily activities of patients and their personal relationship with people around them (e.g., their family). While much research [7,14,[18][19][20][21][22] strongly supports that AD patients have impairment in semantic processing, there are still many knowledge gaps that require further study to fill. The nature is still actively debated particularly concerning where the semantic impairment was caused by the loss of specific knowledge or impairment of access to the knowledge itself [11,19] Therefore, the scope of this research involves observing the semantic-lexical processing utilized by the naming task among AD and HC subjects.…”