Aging, cognitive strategy variations and brain reorganisations – StratAgHem

Age-related declines in cognitive performance have been consistently found in memory and problem solving. However, cognitive performance in older adults sometimes can also match that of young adults. This suggests cognitive and neural compensatory mechanisms. Neuroimaging studies have documented age-related differences in brain activations that are associated with behavioral performance. In particular, older adults sometimes display activations in regions that are not activated by younger adults performing the same tasks. This has been observed using fMRI and ERP techniques. Such age-related brain overactivations have emerged as an important unexpected finding as aging may reveal an enduring neural capacity for functional redistribution of resources in response to neurobiological declines. Determining whether this phenomenon corresponds to processes that are beneficial, detrimental, or inconsequential to cognitive function is a current challenging issue. There is some evidence suggesting that additional recruitment is functional and supportive of cognition in older adults. However, because studies linking age-related differences in brain overactivations to cognitive performance remains spare, and because some results do not support the compensation hypothesis, the question of the functional significance of age-related brain overactivations remains under debate. Another interesting observation is that brain overactivation may appear particularly in effortful task conditions, both in younger and older adults. This suggests that pattern of brain overactivation could be a “normal” way to cope with task difficulty, not specific to the aging brain. However, studies addressing this issue are also spare. Finally, although the compensation hypothesis predicts that the capacity to optimize performance by recruiting alternative brain networks may reflect the use of different cognitive strategies, unknown is the nature of cognitive mechanisms that underlie such postulated compensatory processes. The present project addresses these different issues by focusing on the relationship between aging brain activation and cognitive strategies in memory and arithmetic problem solving, and executive functioning in order to elucidate the functional significance of age-related brain overactivation. In both domains, the general hypothesis under test states that age-related differences observed in brain overactivations are mediated by changes in task specific cognitive strategies and in executive functions. To answer this issue, two series of experiments will be conducted. The first will study the relationship between behavioural memory strategies, executive functioning measures and brain activity measured with ERP technique. The second, addressed the same issue in arithmetic problem solving by using fMRI technique. A variety of behavioral data (memory and arithmetic problem solving strategies, executive functions), and brain-imaging data (fMRI, ERPs) in normal young and older adults will be collected, and related by using both experimental and/or correlational analyses. This will enable us to understand brain activation-related differences as a function of task strategy constraints, participants’ age and executive functioning. The present data should yield answers to at least three challenging issues in the field of aging at the overlap of cognition and neurocognition: (1) to determine first the functional significance of the pattern of brain overactivation observed in aging and more specifically whether it constitutes a compensatory or a detrimental phenomenon, (2) to determine whether the pattern of brain overactivation observed in aging is specific to the aging brain, or a general brain feature to cope with resource-consuming conditions, and (3) to precise the cognitive mechanisms underlying age-related brain overactivation, focusing on the role of memory and arithmetic strategy, and executive functioning.