Speech and language production in Alzheimer’s disease

This special issue presents papers on the characteristics of speech and language production in Alzheimer’s disease (AD), ranging from the level of the single word to discourse. Although language deficits were not historically considered a hallmark of AD, recent updates to diagnostic criteria for AD recognize word-finding difficulties as an early sign, reflecting research findings of the past two to three decades. The papers presented have implications for both theoretical models of production and for clinical assessment. Three main themes emerge from the five papers of this special issue of Aphasiology. First, the studies presented here demonstrate that the investigation of language difficulty in AD has moved beyond the single word level. Whereas anomia has been long identified as an indicator of language difficulties in AD, researchers today recognize the need to examine word-finding difficulties in the context of communication in connected speech. This approach is evident in Abdalla, Rudzicz, and Hirst (this issue), and in Kavé and Goral (this issue). In addition, characterizing lexical retrieval difficulties beyond the single word level extends also to understanding phonetic, phonological, semantic, and morphological aspects of word retrieval, as addressed in the papers of Cera, Ortiz, Bertolucci, and Minett (this issue), Fyndanis et al. (this issue), and Kavé and Goral (this issue). A second, related, theme is the call for automated analysis of language production. If the language abilities and disabilities of individuals with AD are to be analysed in the context of connected speech production, automated analyses could alleviate some of the challenges associated with analysing connected speech, such as the time-consuming and error-prone nature of the work. Both Kavé and Dassa (this issue), and Abdalla et al. address this exciting development. A third theme that emerges from the works presented here concerns stages of severity of the disease. The progressive changes associated with AD are inherent to the nature of the dementia. A challenge that researchers of AD face is determining the extent to which language impairment associated with AD can be examined across a range of individuals and severity levels. Two studies address this issue directly, Fyndanis et al. and Kavé and Dassa (this issue), and other studies have wrestled with it as the authors define their study population. Beyond these themes, each paper contributes to our understanding of specific aspects of language changes in AD. Indeed, in Kavé and Goral’s paper, the manifestation of word finding difficulties in connected speech production are investigated in a meta-analysis. This analysis was conducted on the performance of over one thousand individuals with AD and over one thousand healthy controls. The findings indicate that lexical retrieval difficulties are present in the connected speech deficits found in AD patients. The nature of many of these lexical retrieval difficulties (e.g., use of pronouns, paraphasias), is further characterized in this investigation. The paper by Cera and colleagues addresses whether the underlying nature of word production errors is more properly characterized by motor level (i.e., phonetic) or APHASIOLOGY, 2018 VOL. 32, NO. 1, 1–3 https://doi.org/10.1080/02687038.2017.1390206