This project investigated the role of executive function in mediating age-related differences in higher-order cognitive activities. The major research works completed in this project include two parts: behavioral study and event-related potentials (ERP) study.In the first part, a sample of 142 normal adults between 18 and 85 years of age performed a set of executive function (i.e. attention switching, memory updating, and inhibition of prepotent responses), processing speed (i.e. reaction time, psychophysical speed, and perceptual/motor speed), and several additional cognitive tasks. Hierarchical regression analyses indicated that the proportion of unique age-related variance in executive function measures was related to the complexity of processing speed measures. There was a larger proportion of unique age-related variance in executive function measures after controlling for the variance in simpler speed measures. Moreover, structural equation modeling showed that the mediation effects varied when different types of executive and/or speed variables were considered, and memory updating played an even larger role in mediating age-related differences in cognitive aging than did processing speed; when more complex speed variables were considered, executive variables played a lesser role in mediating age-related
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