Although attention has a central role in age-related decline in cognitive abilities, a barrier to progress, in the cognitive neuroscience of aging, is that little is known regarding the age-related differences in brain structure and function that are relevant for attention. This research addresses the issue of age- related differences in visual attention, from two complementary perspectives: age-related differences in the neural mechanisms associated with visual attention, and the relative influence of different aspects of brain structure and function on age-related differences in measures of visual attention. The theoretical framework for this research proposes that age-related differences in behavioral (attentional) performance represent the combined influences of individual differences in several variables: a) the magnitude of task-related regional activation;b) the functional connectivity (FC) associated with the temporal coherence of the fMRI signal;and c) the integrity of white matter pathways. Five experiments are planned that will examine age-related differences in different aspects of visual search and discrimination. Each experiment will contain separate cohorts of healthy, community-dwelling adults from three age groups: 20-39, 40-59, and 60-79 years of age. Across the experiments, the research will address three specific aims.
The first aim i s to investigate age-related differences in the magnitude and FC of task-related activation. The hypothesis is that age-related differences in activation, within different components of the frontoparietal network, will vary in relation to: the requirement to combine visual features (Experiments 1-2), the selection of relevant features and resistance to attentional capture (Experiments 3-4), and the control of competing responses (Experiment 5).
The second aim i s to investigate age-related differences in resting-state (intrinsic) FC, in terms of the temporal coherence of the spontaneous, low-frequency fluctuations in the fMRI signal. Four intrinsic FC networks (default mode;dorsal and ventral attentional;visual sensory) will be investigated, with the hypothesis that age-related decline in intrinsic FC will vary in magnitude across the networks.
The third aim i s to identify the relative influence of task-related activation, FC, and white matter integrity (from DTI), as mediators of age-related differences in cognitive performance. The hypothesis is that although all of the variables will mediate the relation between age and visual attention, individual differences in white matter integrity have a more direct influence on intrinsic FC than on task-related FC. If the research aims are achieved, the results would impact the cognitive neuroscience of aging, by providing a new integration of neural and behavioral data relevant to visual attention. These data, from healthy individuals, is a necessary foundation for the diagnosis and treatment of cognitive impairments.
This research will yield new, empirical data, from structural and functional brain imaging, regarding age- related differences in the neural mechanisms of attention, in the context of visual detection and discrimination tasks. This research will be relevant to the public health by obtaining new information regarding age-related differences in healthy individuals, which is a necessary basis for the future development of procedures for diagnosing and treating age-related cognitive impairment.
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