Functional changes in the brain associated with differences in cognitive performance

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2 Aging is associated with multiple changes in cognitive performance and brain function. Longitudinal studies show that interindividual differences in cognitive performance increases from early to late adulthood. However, it is less clear how these inter-individual differences in cognition are linked to differences in brain function. In the current study, we used fMRI to link differences in cognitive performance of a visual short-term memory task to differences in activation at a whole-brain level. We used a modularity maximization algorithm to identify brain networks that show similar inter-subject variability. Based on the activity patterns obtained in each of the networks, we used latent-profile analyses to identify subgroups with different profiles of brain activation. The modularity algorithm identified a set of 8 brain networks with different distinct levels of activation across subjects. We distinguished three subgroups of participants with different profiles of brain activation and different level of performance in the task. The first group (n=21) showed significantly lower activation in brain networks involving mostly regions associated with FPCN and FEN, and higher activation in regions involving the visual cortex and the cerebellum. A second group (n=15) showed an opposite pattern of results, displaying higher levels of activation in areas associated with FPCN and FEN and lower activation in visual processing areas and the cerebellum. Finally, the third group (n=66) showed a uniform pattern of brain activation across all the networks. Collectively, these data might suggest the use of different cognitive strategies by each subgroup. These changes in strategies might reflect an adaptation to a working memory cognitive system that is less able to manage representations in a top-down manner. Keywords: fMRI, inter-individual variability, working memory, fronto-parietal control network, visual networks, cognitive strategies.
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