Effets du vieillissement normal sur la mémoire de travail et ses composantes attentionnelles : déclin sur 5 ans et effets de réserve

With increasing life expectancy, it is becoming essential to better understand the cognitive changes associated with normal aging. Working memory (WM) is a limited capacity system that temporarily holds and manipulates a small amount of information; it is a particularly important cognitive function, involved in numerous complex daily activities. A WM impairment affects the whole cognitive functioning and thus has an impact on autonomy. This thesis assesses the age effects on WM and on attentional control functions (ACFs) that underlie this system: inhibition, shifting and updating. We are also interested in the effects of education and cognitively stimulating activities as protective factors on age-related WM decline. The first study (Chapter II) aimed at examining the age effects on WM and ACFs over a five-year period. Participants were evaluated twice over 5 years (Time 1; Sylvain-Roy, Lungu, & Belleville, 2015a) by three complex WM tasks (i.e., reading span, Brown-Peterson and alpha span) and multiple measures of inhibition, shifting and updating. In order to explore the possibility that decline over 5 years is modulated by age, we separated the participants into a “young-old” group (mean age at Time 1: 65.79) and an “old-old” group (mean age at Time 1: 75). Repeated analyses of variance were conducted in order to examine the effect of time and the interaction between time and group. Results showed a significant decline, over 5 years, for all three complex WM tasks and for measures of inhibition and shifting. Results showed no interaction between time and group, which indicated that the old-old group did not show a greater decline relative to young-old participants. This study shows that normal aging is marked by important and pervasive changes in WM and in most ACFs over a relatively short five-year period. Moreover, old-old and young-old participants show a similar rate of decline; theorical and clinical implications will be discussed. The second study (Chapter III) aimed at exploring effects of education and cognitively stimulating activities on WM decline. Simple and multiple linear regressions showed a protective effect of cognitively stimulating activities on decline for the Brown-Peterson task for all participants. Results also showed an interaction between age and education for baseline performances (Time 1) and for decline on the Brown-Peterson task. That is, only young-old participants seemed to benefit from education on baseline performances. This protective effect then recedes, leading to a greater decline over time for young-old compared to old-old participants. No interaction was found between education and cognitively stimulating activities. The other two WM tasks (i.e., reading span and alpha span) did not seem to benefit from protective effects of education or cognitively stimulating activities. This study shows a protective independent effect of education and the practice of cognitively stimulating activities on one complex WM task. Moreover, this study suggests that the impact of some protective factors could vary with age.

Keyphrases: aging, working memory, attentional control functions, education, cognitively stimulating activities