Abstract :
[en] Older adults frequently experience difficulties in lexical retrieval, a phenomenon exacerbated in neurodegenerative disorders such as Alzheimer’s disease (AD). While semantic interference has been widely studied in healthy aging, its role in pathological aging remains less well understood. The present study investigates how semantic context modulates lexical access in aging, with a particular focus on distinguishing healthy elderly participants from those with early-onset AD. Two groups were tested: (1) 55 healthy older adults (33 women; Mage=77.0; MMMSE=29.07), and (2) 27 participants with AD (23 women; Mage=79.48; MMMSE=21.82). The experimental paradigm involved four conditions based on the semantic relation between a picture to be named and a written distractor word: taxonomic, thematic, unrelated, and control (a neutral symbol). Results revealed a main effect of group for both accuracy (F(1,80)=120.56,p<.001,ηp2=.601), and reaction times (F(1,80)=56.58,p<.001,ηp2=.414), with the AD group performing more slowly and less accurately. A main effect of condition was also observed for both measures (Acc: F(2.369,189.497)=18.136,p<.001,ηp2=.185; RTs: F(2.734,218.686)=27.988,p<.001,ηp2=.259) with the neutral condition yielding the fastest responses and the taxonomic condition being the slowest and least accurate. Importantly, an interaction emerged for accuracy (F(2.369,189.497)=8.95,p<.001,ηp2=.101). Taxonomic distractors led to significantly more errors in the AD group. For RTs, no interaction effect was observed but taxonomic distractors paradoxically led to faster responses in the AD group. These findings confirm that shared categorical features among distractors induce competition and slow lexical retrieval (Abdel Rahman & Melinger, 2009; Mcdonagh et al., 2020). Moreover, these insights suggest a possible degradation of the taxonomic conceptual structure in AD.
