Publicação
A multimodal neuroimaging approach to the interplay between stress and aging
| Resumo: | The new trend in modern societies includes changes in the aging and stress exposure profiles. As individuals get older, either healthy or pathologically, several changes occur in body systems, namely in the brain structure and function. This is obviously a complex process characterised by high inter- and intra-individual variability; such variability in the aging process may arise from the interaction of multiple factors, including exposure to stressful experiences across the lifespan. In the present work, using a multimodal neuroimaging and neurocognitive approaches, we characterized the effect of stress on the active and “resting” human brain and its interplay with mood during healthy aging. We explored the impact of stress on decision-making processes, on the activation/deactivation patterns of Resting State Networks (RSNs) and its interplay with mood, on brain structure and function during the aging process. Data shows that chronic stress biases decision-making strategies in humans towards habits, causing an imbalanced activation of the networks that govern decision processes, shifting the activation from the associative to the sensorimotor circuits. These functional changes are paralleled by atrophy of the medial prefrontal cortex and the caudate, and by an increase in the volume of the putamina. Importantly, we demonstrate that after a stress-free period, both the structural and functional changes triggered by stress are reversible and decisions become again goal-directed. Stress triggers also an increased functional connectivity of the default mode (DMN), dorsal attention (DAN), ventral attention (VAN), sensorimotor (SMN), and primary visual (VN) networks, paralleled by impairments in the deactivation patterns of the RSNs and by a constriction of the DMN volume. After recovering from stress, the individuals display a decreased resting functional connectivity in the DMN, VAN and SMN; however, this functional plastic recovery was only partial, as there were still areas of increased connectivity in DAN, SMN and primary VN. Additionally, these subjects display increased deactivations in the DMN, SMN, and auditory network (AN), showing a normalization of the deactivation pattern in RSNs after recovery from stress. Finally, we dissect the critical influence of stress and mood in brain structure and function, with these variables interacting with each other and acting as mediators across the lifespan. This interplay is most evident at combined high stress and depressive mood levels, accelerating the typical age-induced decline or alternatively reducing or even reversing the normal aging impact. In this thesis we reveal the effects of stress on the active and “resting” human brain and its interplay with mood during the healthy aging process. We conclude that stress biases decisionmaking strategies accompanied by brain structural and functional reorganizations, impacting on selective activation/deactivation patterns of RSNs with concomitant volumetric atrophies. Along with mood, stress has also a critical influence, in brain structure and function during the lifespan. The present study contributes to clarify combined stress and mood effects during the aging decline, paving the way for interventional therapies that empower stress coping mechanisms in different phases of life. |
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| Autores principais: | Soares, José Miguel |
| Assunto: | Ciências Médicas::Ciências da Saúde |
| Ano: | 2014 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | The new trend in modern societies includes changes in the aging and stress exposure profiles. As individuals get older, either healthy or pathologically, several changes occur in body systems, namely in the brain structure and function. This is obviously a complex process characterised by high inter- and intra-individual variability; such variability in the aging process may arise from the interaction of multiple factors, including exposure to stressful experiences across the lifespan. In the present work, using a multimodal neuroimaging and neurocognitive approaches, we characterized the effect of stress on the active and “resting” human brain and its interplay with mood during healthy aging. We explored the impact of stress on decision-making processes, on the activation/deactivation patterns of Resting State Networks (RSNs) and its interplay with mood, on brain structure and function during the aging process. Data shows that chronic stress biases decision-making strategies in humans towards habits, causing an imbalanced activation of the networks that govern decision processes, shifting the activation from the associative to the sensorimotor circuits. These functional changes are paralleled by atrophy of the medial prefrontal cortex and the caudate, and by an increase in the volume of the putamina. Importantly, we demonstrate that after a stress-free period, both the structural and functional changes triggered by stress are reversible and decisions become again goal-directed. Stress triggers also an increased functional connectivity of the default mode (DMN), dorsal attention (DAN), ventral attention (VAN), sensorimotor (SMN), and primary visual (VN) networks, paralleled by impairments in the deactivation patterns of the RSNs and by a constriction of the DMN volume. After recovering from stress, the individuals display a decreased resting functional connectivity in the DMN, VAN and SMN; however, this functional plastic recovery was only partial, as there were still areas of increased connectivity in DAN, SMN and primary VN. Additionally, these subjects display increased deactivations in the DMN, SMN, and auditory network (AN), showing a normalization of the deactivation pattern in RSNs after recovery from stress. Finally, we dissect the critical influence of stress and mood in brain structure and function, with these variables interacting with each other and acting as mediators across the lifespan. This interplay is most evident at combined high stress and depressive mood levels, accelerating the typical age-induced decline or alternatively reducing or even reversing the normal aging impact. In this thesis we reveal the effects of stress on the active and “resting” human brain and its interplay with mood during the healthy aging process. We conclude that stress biases decisionmaking strategies accompanied by brain structural and functional reorganizations, impacting on selective activation/deactivation patterns of RSNs with concomitant volumetric atrophies. Along with mood, stress has also a critical influence, in brain structure and function during the lifespan. The present study contributes to clarify combined stress and mood effects during the aging decline, paving the way for interventional therapies that empower stress coping mechanisms in different phases of life. |
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