In the present proposal, we seek to integrate our years of behavioral work on the cognitive neuroscience of aging with our recent imaging work. The paradox we propose to investigate is as follows. It is the case that cognitive function declines reliably across the lifespan. Yet, rather than neural activations declining along with the cognitive behavior, many investigators have reported evidence for increased frontal activation and more distributed frontal activation with age, particularly bilateral activation. Despite the importance of the finding of increased and more distributed frontal recruitment with age, virtually nothing is known about the normative age when this shift to more distributed frontal lobe function occurs, and whether bilateral recruitment in middle-age is indicative of cognitive health or cognitive decline. We investigate in the present proposal whether middle-aged adults who show patterns of frontal recruitment more similar to elderly will have lower cognitive performance and show decreased function in other neural areas. A second focus of the proposed work relates to our recent findings where we have isolated 2 potential mechanisms (hippocampal function, and neural selectivity in the ventral visual cortex) that we believe to be important determinants of both frontal lobe function and memory performance in older adults. We have demonstrated, like others, that older adults recruit additional frontal areas relative to young on both working memory (Park et al., 2003) and long-term memory (Gutchess et al., 2005) tasks. We also have consistently noted decreased hippocampal function accompanying the increased frontal involvement, and found a direct relationship between the 2, leading us to propose that the increased frontal recruitment in old is at least partially due to decreased hippocampal engagement (Park &Gutchess, 2005). We also have found compelling evidence for decreased neural specialization in the ventral visual cortex with age (Park et al., 2004;Chee et al., in press), and we are able to develop a specific index of neural """"""""dedifferentiation"""""""" in ventral visual cortex. We hypothesize that this decreased specialization of sensory cortex is an important factor in enhanced frontal recruitment with age. In sum, in this new project, we propose to conduct the neuroimaging analog of the large lifespan behavioral studies that have come out of our lab (Park et al., 996, 2002). We propose to collect neural data on multiple cognitive tasks, as well as to characterize subjects with a behavioral battery. This work will provide what will be, perhaps, the first lifespan characterization of neurocognitive aging, through an integration of both neuroimaging and behavioral data. We will collect a sample of sufficient size to utilize an individual differences approach, paying particular attention to neural selectivity in ventral visual cortex and hippocampal function as predictors of behavioral performance as well as prefrontal activation. Finally, we propose to integrate structural measures of cortical thinning with behavioral and neural data, and expect that subjects who show cortical thinning in the sensory areas beginning in middle-aged, will be most likely to show neural recruitment patterns typical of older adults.
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