Naming as a window to word retrieval changes in healthy and pathological ageing: Methodological considerations.

Abstract

Word retrieval skills change across the lifespan. Permanent alterations in the form of decreased accuracy or increased response time can be a consequence of both normal ageing processes or the presence of acquired and neurodegenerative disorders (e.g., aphasia and dementia). Despite the extensive literature exploring the neuroanatomical underpinnings of word retrieval, psycholinguistic, biolinguistic and theoretical explanations, and the vast amount of evidence from primary and secondary language disorders, the best approach to consistently capture these changes is yet to be discovered. The goal of this paper is to determine which method(s) stand(s) as the most suitable candidate(s) to provide an accurate picture of word retrieval in the oral production of different groups of adult speakers, including cases of healthy ageing, preclinical Alzheimer's disease (AD), mild cognitive impairment (MCI), aphasia and dementia. Using an integrative review of recent peer-reviewed journal articles, we provide an overview of the different behavioural methods traditionally used to measure oral naming skills in research-oriented and clinical protocols and discuss their main advantages and limitations. Most existing studies are based on the results of people with diagnosed language disorders. Despite the growing interest, the reliability of the majority of the tasks to detect subtle changes associated with healthy ageing, MCI and preclinical AD are yet to be demonstrated, and the delicate balance between informativeness and efficiency (especially in terms of administration time and variable control) in experimental protocols is yet to be achieved. In this article we propose the pursuit of an integrative overarching methodology to characterize all naming deficits (from anecdotal to permanent) and all adult populations (from healthy to pathological ageing). A combination of spontaneous speech data and results from structured tasks stands as the best approach to capture changes in word retrieval skills of adult speakers with and without observable deficits. This review can guide future reflections on the necessary prerequisites of purpose-oriented, sensitive and reliable protocols for the detection of incipient word retrieval problems, thus contributing to the early diagnosis and the design of personalized multicomponent treatments. What is already known on this subject Word retrieval skills change during adulthood as a consequence of the neurological degradation associated with ageing. These changes are more dramatic in the event of acquired and neurodegenerative disorders. Numerous studies based on people with observable language disorders have addressed the multiplicity of factors involved in word retrieval and provided evidence of potential loci of impairment from a neuroanatomical, cognitive and/or (psycho-)linguistic perspective. What this paper adds to existing knowledge This study focuses on methodological strategies to assess naming skills and provides a reflection on generally accepted good practices and unresolved challenges to inform task selection, emphasizing the necessity for a combination of methods to best capture the actual problems and needs of people confronting word retrieval difficulties in their daily lives. Task selection, variable control and administration time stand as key concepts to adjust to the requirements of research and clinical contexts. What are the potential or actual clinical implications of this work? The results of this review can orient future research towards the creation of sensitive, reliable and (ecologically) valid materials for the (early) detection of word retrieval deficits and for the customization of treatment protocols to alleviate or palliate their effects.