Inter-individual variability in cognitive aging: Neural mechanisms, reserve processes and malleability of neuroprotective processes

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Canada's population of seniors is growing rapidly. By 2031, people over age 65 will represent 25% of the Canadian population. Understanding the cognitive and brain changes that occur during aging is thus critically important. Remarkably, some older adults are more resistant to brain aging. Our research team seeks to understand how and why this occurs. To answer these questions, we will rely on the cognitive reserve model, which proposes that differences in brain activation and/or connectivity allow some individuals to better maintain cognition despite the presence of neuropathology or structural brain changes. PART 1 will examine the brain mechanisms underlying inter-individual differences using functional magnetic resonance imaging, a technique that measures brain activation and connectivity between brain regions. Activation and connectivity will be compared as a function of older adults' level of education and their participation in cognitively stimulating activities over their lifetime. Brain function will be measured while participants complete inhibition or updating tasks. Inhibition refers to the ability to refrain from an action that is not appropriate to the task at hand, while updating refers to the ability to remove items from memory that are no longer useful. We will determine whether differences in brain activation or connectivity protect against the adverse effects of age-related changes in brain anatomy. PART 2 will examine the possibility of using cognitive training to create a reserve later in life. We will examine whether the brain changes induced by training updating or inhibition capacities differ according to an individual's level of education or lifelong levels of cognitive engagement. We will also assess whether cognitive training normalizes activation and connectivity in people with lower levels of education or engagement. Finally, PART 3 will focus on transfer, which is the ability of an intervention to improve abilities that have not been directly trained. Finding generalizability is of great importance because it helps demonstrate that cognitive training can be a relevant approach to improving cognitive health and quality of life in older adults. We will use immersive virtual reality as a training medium because there is strong evidence that transfer is optimal when the training reproduces the conditions in which transfer is expected. We will also develop a program based on the episodic specificity induction technique, which involves the detailed retrieval of a past experience. This will determine under which conditions the effects of interventions generalize to tasks that have not been directly trained. Overall, this research program will contribute to understanding how memory and the brain change and adapt with age and make novel prevention strategies available for older Canadians concerned about their cognitive health.