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.
Highlights
Neuroanatomical correlations of naming and lexical-semantic memory are not yet fully understood
A diagnosis of amnestic mild cognitive impairment (aMCI) was determined if the clinical history and cognitive performance pointed to an exclusive memory deficit and Clinical Dementia Rating (CDR)[14] score of 0.5, with an obligatory and exclusive memory score of 0.5
With regard to Boston Naming Test (BNT) total score, Alzheimer’s disease (AD) patients performed worse than both aMCI patients and controls (p
Summary
Abstract – Neuroanatomical correlations of naming and lexical-semantic memory are not yet fully understood. Several hypotheses have been proposed to explain how lexical-semantic memory is processed and stored in the brain, and these have been guided by two main general models: a parallel distributed representation,[2] comprising a homogeneous network of equivalent neuronal units that process every aspect of semantics, and a center processing model, which assumes that all memory elements are encoded in a delimited area of the brain. The most striking evidence of deterioration of this generalizing capacity, manifested initially by semantic naming errors production, is semantic dementia (SD), in which there is a degeneration of the anterior portions of the temporal lobes, and is more intense on the left side These patients have difficulties in naming everyday objects and knowing their properties, with impairment of all kinds of concepts in the context of otherwise well-preserved cognition, including episodic memory. As proposed by other authors, the temporal lobe, its anterior part, may constitute a convergence zone for information coming from brain regions responsible for processing different aspects of knowledge.[4,5] It has been suggested that the temporal lobe object representation system may be organized hierarchically, with increasing convergence and integration of information occurring along its posterior to anterior axis.[6]
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