Olfactory performance and linguistic ability in Alzheimer's disease
Résumé
Background Olfactory dysfunction and language impairment has been frequently reported to occur in the early stages of Alzheimer's disease. The purpose of this study is to investigate (a) effect of Alzheimer's disease on the processing of odour ; (b) influence of olfactory stimulation on spontaneous spoken language. Methods 17 patients with Alzheimer's disease and 17 age-, sex-, education-matched normal controls participated in this study. 3 odorants (strawberry, mint, fish) were presented. For each odour, the participants were asked to rate pleasantness, intensity, and familiarity. Then, they produced spontaneous discourse about their memories, feelings, psycho-physical impressions relative to presented ordour. Finally, the subjects were asked to identify odour by using a board containing four pictures (target item, semantic distractor, phonological distractor, unrelated distractor). Results The results show that (i) the intensity scores were lower in Alzheimer patients than healthy control subjects (p < 0.001). (ii) no difference between the two groups for pleasantness and familiarity (iii) a significant decrease in odor identification with Alzheimer's disease (p < 0.01). We observed also different patterns of language between Alzheimer's and control's discourse. While lexical richness did not differ significantly between the two groups, patient's discourse is marked by use of high frequency lexical. And, only the normal subjects employed hyponyms. Conclusions In this paper, we discuss the prospect of the use of olfactory assessment for early detection of the disease and the contribution of linguistic to a better understanding of Alzheimer's disease.