Naming unique entities in the semantic variant of primary progressive aphasia and Alzheimer's disease: Towards a better understanding of the semantic impairment

Abstract

While the semantic variant of primary progressive aphasia (svPPA) is characterized by a predominant semantic memory impairment, episodic memory impairments are the clinical hallmark of Alzheimer's disease (AD). However, AD patients also present with semantic deficits, which are more severe for semantically unique entities (e.g. a famous person) than for common concepts (e.g. a beaver). Previous studies in these patient populations have largely focused on famous-person naming. Therefore, we aimed to evaluate if these impairments also extend to other semantically unique entities such as famous places and famous logos. In this study, 13 AD patients, 9 svPPA patients, and 12 cognitively unimpaired elderly subjects (CTRL) were tested with a picture-naming test of non-unique entities (Boston Naming Test) and three experimental tests of semantically unique entities assessing naming of famous persons, places, and logos. Both clinical groups were overall more impaired at naming semantically unique entities than non-unique entities. Naming impairments in AD and svPPA extended to the other types of semantically unique entities, since a CTRL>AD>svPPA pattern was found on the performance of all naming tests. Naming famous places and famous persons appeared to be most impaired in svPPA, and both specific and general semantic knowledge for these entities were affected in these patients. Although AD patients were most significantly impaired on famous-person naming, only their specific semantic knowledge was impaired, while general knowledge was preserved. Post-hoc neuroimaging analyses also showed that famous-person naming impairments in AD correlated with atrophy in the temporo-parietal junction, a region functionally associated with lexical access. In line with previous studies, svPPA patients' impairment in both naming and semantic knowledge suggest a more profound semantic impairment, while naming impairments in AD may arise to a greater extent from impaired lexical access, even though semantic impairment for specific knowledge is also present. These results highlight the critical importance of developing and using a variety of semantically-unique-entity naming tests in neuropsychological assessments of patients with neurodegenerative diseases, which may unveil different patterns of lexical-semantic deficits.

The relationship between response consistency in picture naming and storage impairment in people with semantic variant Primary Progressive Aphasia

“…In the present study, we address these issues by assessing item-by-item consistency within modality over repeated presentations in a case series of ten people with svPPA. Our sample size matches or even exceeds that of most studies which have previously studied consistency and storage impairments (e.g., Bozeat et al, 2000 (n = 10); Coughlan & Warrington, 1981 (n = 1); Hodges et al, 1995 (n = 1)) or other aspects of language production in svPPA (e.g., Marques & Charnallet, 2013 (n = 6); Montembeault et al, 2017 (n = 9)). We not only examined consistency between correct/incorrect responses but also between semantic errors and other error responses, while at the same time controlling for effects of psycholinguistic variables such as familiarity and frequency on naming.…”

Semantic Feature Training in Combination with Transcranial Direct Current Stimulation (tDCS) for Progressive Anomia

“…Such variability precludes the application of a one-size-fits-all approach to language intervention and its formal assessment (e.g., Montembeault et al, 2016). For example, treatments targeting motor speech fluency are not readily applicable for patients with svPPA whose output is typically fluent.…”

Connected Speech Features from Picture Description in Alzheimer’s Disease: A Systematic Review

“…In their picture descriptions, AD patients tend to use more high-frequency words than controls. In the studies surveyed, this effect appeared in overall lexical content [93] and specifically in verbs a matter of debate [16]. Alternatively, discourse efficiency has also been linked to executive function [117], which is known to be impaired in AD [118].…”