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Objective: This study aimed to test whether the level of cognitive resources explain the engagement in physical activity across aging and whether the age-related decline of cognitive resources precede the decline in physical activity. Methods: Data from 105,206 adults aged 50 to 90 years from the Survey of Health, Ageing and Retirement in Europe (SHARE) were used in adjusted linear mixed models to examine whether the engagement in moderate physical activity and its evolution across aging was dependent on cognitive resources. Cognitive resources and physical activity were measured 5 times over a 12-year period. Delayed recall, verbal fluency, and the level of education were used as indicators of cognitive resources. The frequency of engagement in moderate physical activity was self-reported. Dynamic structural equation models (SEM) were used to assess the temporal precedence of changes in cognitive resources and physical activity. Results: Results showed that lower cognitive resources were associated with lower levels and steeper decreases in moderate physical activity across aging. Results further revealed a time-ordered effect with a stronger influence of cognitive resources (delayed recall and verbal fluency) on subsequent changes in moderate physical activity than the opposite. Conclusion: These findings suggest that, after age 50, the level of engagement in moderate physical activity and its trajectory depend on the availability of cognitive resources.

Adverse childhood experiences, depression, and functional dependence are inter-related. However, mechanisms underlying this relation remain unclear. Here, we investigated the potential of depression to mediate the effect of adverse childhood experiences on functional dependence in older age and whether physical activity moderated this mediation. Data from 25,775 adults aged 62±9 years from the Survey of Health Ageing and Retirement in Europe (SHARE) was used in adjusted linear mixed-effect models to test whether depression mediated the associations between adverse childhood experiences and functional dependence in activities of daily living (ADL) and instrumental activities of daily living (IADL) and whether physical activity moderated these mediations. As expected, adverse childhood experiences were positively associated with ADL (b = .040 for 0 vs. 1 and b = .067 for 0 vs. ≥2 adverse childhood experiences) and IADL (b = .046 for 0 vs. 1 and b = .076 for 0 vs. ≥2 adverse childhood experiences). Both associations were mediated by depression. Physical activity reduced the effect of adverse childhood experiences on depression (b = -.060 for 0 vs. 1 and b = -.135 for 0 vs. ≥2 adverse childhood experiences) and canceled the effect of depression on functional dependence in ADL (b = .073) and IADL (b = .100), thereby eliminating the effect of adverse childhood experiences on functional dependence. Physical activity cancels the impact of adverse childhood experiences on functional dependence. In inactive individuals, the effect of adverse childhood experiences on functional dependence (ADL and IADL) is mediated by depression.

Humans can navigate through challenging environments (e.g., cluttered or uneven terrains) by modifying their preferred gait pattern (e.g., step length, step width, or speed). Growing behavioral and neuroimaging evidence suggests that the ability to modify preferred step patterns requires the recruitment of cognitive resources. In children, it is argued that prolonged development of complex gait is related to the ongoing development of involved brain regions, but this has not been directly investigated yet. Here, we aimed to elucidate the relationship between structural brain properties and complex gait in youth aged 9 - 18 years. We used volumetric analyses of cortical grey matter (GM) and whole brain voxel-wise statistical analyses of cortical white matter (WM), and utilized a treadmill-based precision stepping task to investigate complex gait. Moreover, precision stepping was performed on step targets which were either unperturbed or perturbed (i.e., unexpectedly shifting to a new location). Our main findings revealed that larger unperturbed precision step error was associated with decreased WM microstructural organization of tracts that are particularly associated with attentional and visual processing functions. These results strengthen the hypothesis that precision stepping on unperturbed step targets is driven by cortical processes. In contrast, no significant correlations were found between perturbed precision stepping and cortical structures, indicating that other (neural) mechanisms may be more important for this type of stepping. ispartof: Brain Structure and Function vol:223 issue:4 pages:2039-2053 ispartof: location:Germany status: published

There is a convergence in the literature toward a critical role for the basal ganglia in action selection. However, which substructures within the basal ganglia fulfill this role is still unclear. Here we used shape analyses of structural magnetic resonance imaging data to determine the extent to which basal ganglia structures predict performance in easy and complex multilimb reaction-time tasks in young and old adults. Results revealed that inward deformation (i.e., local atrophy) of the nucleus accumbens and caudate were predictive of longer action selection times in complex conditions, but not in easy conditions. Additionally, when assessing the relation between behavioral performance and the shape of the left nucleus accumbens in the two age groups separately, we found a significant performance-structure association in old, but not young adults. This result suggests that the relevance of the nucleus accumbens for the process of action selection increases with age. Hum Brain Mapp 37:4629-4639, 2016. © 2016 Wiley Periodicals, Inc. ispartof: Human Brain Mapping vol:37 issue:12 pages:4629-4639 ispartof: location:United States status: published

As outlined by strong and unexplained discrepancies in the literature, whether proprioceptive control of movement is altered in physiological adult ageing is still under debate. In an attempt to unify these previous results, the three studies of the present thesis proposed to test the effects of muscle, attentional and temporal stresses on the proprioceptive control of movement, respectively. The common task of these three studies was an ankle contralateral concurrent matching task. To test the effects of muscle, cognitive and temporal stresses on the proprioceptive control performance of older and young adults, participants performed the matching task in fatigue and no-fatigue, single and dual task, and self-paced and fast speed conditions, respectively. To assess participants' proprioceptive performance, error, temporal and kinematic variables were analysed. The results of the first study showed that performance in the matching task was altered by muscle fatigue only when the reference was actively maintained. To avoid confounding fatigue effects with other effects, the second and third studies assessed the matching task with a reference passively maintained. The results of these studies first showed that end-point performance in the matching task was similar in young and older adults in the absence of cognitive and temporal stress. However, the strategies the participants used to reach the end-point position were different in young and older adults. Second, the addition of a cognitive or temporal stress degraded the proprioceptive control performance in older adults as compared to the young ones. Taken together, these results emphasize a decreased resilience to stressors in older adults as compared to young ones and highlight the age-related alteration in proprioceptive control of movement., Comme l'indiquent les divergences observées dans la littérature, la question de l'existence d'une modification du contrôle proprioceptif du mouvement au cours du vieillissement physiologique de l'adulte fait encore débat. Pour mieux comprendre ces divergences, trois études ont été réalisées afin de tester les effets de contraintes d'origines musculaire, attentionnelle et temporelle sur le contrôle proprioceptif du mouvement. La tâche commune à ces trois études était une tâche d'estimation active directe controlatérale de la position de la cheville. Les effets de contraintes musculaire, cognitive et temporelle sur les performances de contrôle proprioceptif ont été respectivement testés dans les conditions de fatigue et non fatigue, de simple et double tâche, et de vitesses libre et rapide. Pour évaluer la performance de contrôle proprioceptif, les erreurs totale, variable et constante ainsi que des variables temporelles et cinématiques ont été analysées. Chez les participants jeunes, les résultats de la première étude ont montré que la fatigue musculaire altère la performance d'estimation de position lorsque la cheville de référence est maintenue activement en position mais pas lorsqu'elle est maintenue passivement. Afin d’éviter de confondre un effet de la fatigue musculaire éventuellement induite par la répétition de la tâche d'estimation de position, les deuxième et troisième études ont été réalisées avec la référence maintenue passivement en position. Les résultats de ces deux études ont montré qu'en l'absence de contraintes cognitive et temporelle, la performance de positionnement final dans la tâche proprioceptive est comparable entre les adultes jeunes et âgés. Cependant, la stratégie utilisée pour atteindre cette position est différente selon l'âge. Les résultats ont également montré que l'adjonction d'une contrainte cognitive ou temporelle produit une dégradation de la performance de contrôle proprioceptif des adultes âgés par rapport aux adultes jeunes. Dans l’ensemble, ces résultats montrent que la capacité des adultes âgés à résoudre les problèmes posés par les contraintes environnementales est inférieure à celle des adultes jeunes et mettent en évidence la modification de contrôle proprioceptif du mouvement qui s'opère au cours du vieillissement physiologique.

International audience; The present paper tried to provide a review of the different works investigating the attentional cost of postural control. Within the context of a double task, the attentional demand associated to postural control depends on various factors such as (1) the automatic or voluntary focalisation of attention on postural control, (2) the available sensory information, (3) the nature and complexity of the postural task, (4) the subjects' age, and/or (5) the level of subjects' sensory-motor expertise or deficits. Following a brief presentation of the double task paradigm in the context of postural control, the effects of these different factors are analysed more specifically.

International audience; L'objectif de cette étude est de déterminer l'effet d'un exercice musculaire fatigant les fléchisseurs plantaires sur les capacités proprioceptives au niveau de la cheville. Pour ce faire, 20 sujets ont participé soit à une tâche de positionnement comparé de la cheville, soit à une tâche de force comparée dans les conditions de Non fatigue et de Fatigue des fléchisseurs plantaires de la cheville dominante. Les résultats montrent des performances dégradées en condition Fatigue. Dans ce contexte, il est possible que l'instabilité posturale observée en condition de fatigue musculaire localisée au niveau des fléchisseurs plantaires dans de récentes études résulte d'une altération des capacités proprioceptives au niveau de la cheville.