Entraîner le contrôle attentionnel chez la personne âgée : perspective comportementale et cérébrale

The main objective of this thesis was to evaluate the effect of cognitive interventions on attentional control using behavioral measures and functional magnetic resonance imaging (fMRI). The thesis comprises five empirical articles. The aim of the first study (Chapter II) was to examine the cause of age-related differences in attentional control. The results suggest that, compared to younger adults, older participants have more difficulty varying the level of attention to be allocated to each task according to the attentional focus that is required, reflecting a difficulty with attentional control. The second study (Chapter III) aimed to compare the effectiveness of three types of computerized attentionnal training in older adults. The results show specific effects depending on the type of training received. Only the older participants who followed the VARIABLEpriority training, in which they had to vary the level of attention allocated to each task across several blocks, showed improvement in their attentional control skills following training. This improvement cannot be explained by repeated practice in the tasks under focused attention or in the dual-task condition without attentional variation. The aim of the third study (Chapter IV) was to assess whether the benefits of VARIABLE-priority training could transfer to tasks similar to those trained and to tasks that are more representative of everyday life, using an immersive dual-task paradigm in virtual reality (VR). The results show that VARIABLE-priority training improves attentional control abilities and, for the first time, that the beneficial effects of this training can be transferred to a dual-task paradigm in VR in older adults. Furthermore, we show that older adults benefit as much, if not more than younger adults, from an intervention aiming to improve attentional control, and that age does not have an effect on the transfer effects observed. The fourth study assessed (Chapter V) the impact of attentional training on changes in fMRI activation. The results suggest that the brain is highly plastic, even in old age, and that the changes in activation are different depending on the type of intervention. VARIABLEpriority training, which aims to teach attentional control strategies and metacognitive abilities, is the only one that produces increases in activation in a frontal region involved in multitasking and attentional control. Repeated practice of a task under focused attention, on the other hand, causes decreases in activation in regions that were previously recruited. Finally, the aim of the fifth study (Chapter VI) was to evaluate the time course of activation changes across three fMRI sessions. An increase in activation followed by a plateau in regions related to the strategies learned for the VARIABLE-priority training is observed, while the activation changes following repeated practice are characterized by an inverse U-shape function. The results of the latter study show that activation changes are non-linear during training and, similarly to the results obtained in the fourth study, are modulated by the type of intervention followed.

Keyphrases: Normal aging, Cognitive training, Attentional control, Functional magnetic resonance imaging