Investigating the shifting architectures of brain and cognition in older adulthood

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Psychological and neuroscience studies of cognitive aging are disproving the fallacy that cognitive aging equals cognitive decline. The true story of cognitive aging is one of both gains as well as losses. With age comes an expanding repertoire of knowledge and life experience that can help navigate the routines - and the surprises - of daily life. When and how past knowledge is accessed to guide behavior can influence how successfully older adults are able to reason, problem-solve, and plan in their everyday lives. Within the brain, complex cognitive abilities such as reasoning and problem-solving engage frontal cortices and functionally connected regions that together form an `executive network'. However, accessing one's store of prior knowledge, including representations of oneself and the world engages a different set of regions known as the `default network'. It is well known that complex cognitive abilities decline over the adult lifespan. However, evidence is beginning to suggest that older adults may be able to leverage their relatively larger store of knowledge and experiences to mitigate these declines. But how this happens in the brain is not well understood. My work has shown that one potential neural mechanism that may support the engagement of prior knowledge during complex cognitive tasks is the interaction of brain networks supporting complex cognition (i.e. the executive network) and activation of stored knowledge representations (i.e. the default network). In other words, increased default-executive coupling may serve as a neural conduit allowing prior knowledge to influence cognitive functioning in later life. My colleague and I have labeled this the `Default-Executive Coupling Hypothesis of Aging (DECHA). The goal of this research proposal is to directly test the DECHA model using functional neuroimaging (fMRI) and neurostimulation (transcranial magnetic stimulation - TMS) methods. We will examine patterns of default-executive coupling associated with performance on tasks where prior knowledge is known to either (i) facilitate or (ii) hinder task performance. We predict that neural markers of DECHA (derived from fMRI and neurostimulation-based studies) will be associated with better task performance for older adults when prior knowledge is relevant, and worse performance when it is irrelevant, to task goals. This proposal will interrogate a novel theory of neurocognitive aging that may serve to reconcile patterns of age-related brain and behavioural change. If the hypotheses are realized, this research will identify the DECHA as a candidate neural mechanism underlying greater reliance on prior knowledge to support cognitive functioning in older adulthood. Further, these findings would provide the first network neuroscience model to predict the full spectrum of neurocognitive aging, encompassing both cognitive gains and losses.