Abstract
Aging of brain structure and function is a complex process characterized by high inter- and intra-individual variability. Such variability may arise from the interaction of multiple factors, including exposure to stressful experience and mood variation, across the lifespan. Using a multimodal neuroimaging and neurocognitive approach, we investigated the association of stress, mood and their interaction, in the structure and function of the default mode network (DMN), both during rest and task-induced deactivation, throughout the adult lifespan. Data confirmed a decreased functional connectivity (FC) and task-induced deactivation of the DMN during the aging process and in subjects with lower mood; on the contrary, an increased FC was observed in subjects with higher perceived stress. Surprisingly, the association of aging with DMN was altered by stress and mood in specific regions. An increased difficulty to deactivate the DMN was noted in older participants with lower mood, contrasting with an increased deactivation in individuals presenting high stress, independently of their mood levels, with aging. Interestingly, this constant interaction across aging was globally most significant in the combination of high stress levels with a more depressed mood state, both during resting state and task-induced deactivations. The present results contribute to characterize the spectrum of FC and deactivation patterns of the DMN, highlighting the crucial association of stress and mood levels, during the adult aging process. These combinatorial approaches may help to understand the heterogeneity of the aging process in brain structure and function and several states that may lead to neuropsychiatric disorders.
Highlights
Magnetic resonance imaging (MRI) studies, including volumetric, diffusion and functional analysis, have provided new insights into the structural and functional modulation of brain regions and networks across the lifespan
Using a multimodal neuroimaging and neurocognitive approach, we investigated the association of stress, mood and their interaction, in the structure and function of the default mode network (DMN), both during rest and taskinduced deactivation, throughout the adult lifespan
At rest, increased age was significantly correlated with less functional connectivity (FC) in the DMN, in the right anterior cingulate cortex, frontal medial orbitofrontal and precuneus relative to the normal global DMN signal (Table 2; Fig. 2a1)
Summary
Magnetic resonance imaging (MRI) studies, including volumetric, diffusion and functional analysis, have provided new insights into the structural and functional modulation of brain regions and networks across the lifespan. Prolonged stress exposure impairs spatial working memory, perceptual attention, behavioral flexibility and decision making both in rodents and humans in association with structural changes in several brain regions that are common to the DMN (Yuen et al 2012; Dias-Ferreira et al 2009; Soares et al 2012) Most of these maladaptive structural and functional responses to increased chronic stress were reported in young and middle-aged subjects and were in part shown to be reversible (Bian et al 2012; Soares et al 2012; Sousa et al 2000). Understanding the association between structural and functional brain alterations, in combination with life experiences, across the lifespan, may help to understand part of this variability, namely in cognitive performance We address this interaction using a neuroimaging approach to assess the individual and interactive association between aging, stress, mood and the DMN, both during rest and task-induced deactivation. We expect a significant interaction of higher stress (based on our previous studies) and mood levels on the normal aging DMN connectivity decrease pattern, especially due to their potential opposite effects
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