Functional connectivity of resting-state, working memory and inhibition networks in perceived stress.

Experimental imaging studies on the effects of acute stress have revealed functional changes in the amygdalae, hippocampi and medial frontal cortices. However, much less is known about the association between perceived stress and neurological function which may have implications for the development of stress related disorders. Participants completed a working-memory task and an inhibition task whilst undergoing a functional magnetic resonance imaging (fMRI) scan. Task related and resting-state fMRI data from 22 women and 24 men were analysed to investigate changes in task activations and functional connectivity associated with perceived stress over the past month. Analyses were stratified by gender due to gender differences in the stress response. Stress was associated with faster working memory response time in women, but not men. Stress was not associated with any differences in task activations in either gender. There were many significant associations between stress and connectivity: findings in women were consistent with increased emotional regulation; men exhibited decreases in connectivity between affective processing areas during the tasks and showed no relation between perceived stress and resting-state connectivity; very few of the within gender differences were significantly different between gender. Dysregulated connectivity between areas involved in the neural stress response and self-referential thoughts (e.g. the default mode network) suggests that perceived stress may have a subtle impact on cognitive processing and neural correlates.

Working memory, age and education: A lifespan fMRI study.

Ageing is associated with grey matter atrophy and changes in task-related neural activations. This study investigated the effects of age and education on neural activation during a spatial working memory task in 189 participants aged between 20-80 years old, whilst controlling for grey matter density. Age was related to linear decreases in neural activation in task activated areas, and this effect was no longer significant when adjusting for education or accuracy. Age was also related to cubic increases in neural activation in non-task related areas, such as the temporal gyrus, cuneus and cerebellum when adjusting for accuracy and education. These findings support previous lifespan datasets indicating linear age-related decreases in task activation, but non-linear increases in non-task related areas during episodic memory tasks. The findings also support past studies indicating education offers a form of cognitive reserve through providing a form of neural compensation and highlights the need to consider education in ageing studies.

A Comprehensive Analysis of Connectivity and Aging Over the Adult Life Span.

Aging has been associated with decreased intra- and internetwork connectivity during rest and task. Recent work has shown the influential role of the salience network over the default mode network (DMN) and executive control network (ECN). This study comprehensively investigates age-related changes in intra- and internetwork connectivity and effective connectivity between the DMN, ECN, and salience network across the adult life span. Two hundred ten participants completed a working memory task, an inhibition task, and a resting-state functional magnetic resonance imaging scan. Networks were extracted using independent component analysis; then, regression analyses and t-tests between three age groups, 21-40 (younger), 41-60 (middle), and 61-80 (older), were conducted. Older age was associated with decreased intranetwork connectivity. Functional network connectivity analyses revealed older age was associated with increased internetwork connectivity between the salience network and the ECNs and DMNs. In both cases, the effects were more pronounced in the tasks compared to resting state. Granger causality analyses indicated the salience network was influenced by the DMN and ECN in all age groups during both tasks, but not rest. However, middle adults showed increased influence from the salience network to the right ECN compared to younger adults during the flanker task. Taking everything into account, these findings indicate the role of the salience network changes over the life span, which may have implications for the early detection of pathophysiology in older adults.