Executive function is higher-order, strategic cognitive activity which controls and integrates other cognitive actions. This thesis investigated the role of executive function in cognitive aging and included two parts: behavioral study and event-related potentials (ERP) study.
In the first part, the reliability of nine measures, and the construct validity of three underlying executive functions (i.e. task switching, inhibition of prepotent responses, and memory updating) was verified. Then, the role of different kinds of executive function in cognitive aging was explored using structural equation modeling (SEM) methods, and the relative contribution of executive function and mental speed to cognitive aging was compared. Based on the result of behavioral study, in the second part, the relevant ERP components according to memory updating, and age-related changes were explored subsequently.
The main findings of the behavioral part were that: First, the referring nine executive measures were highly reliable. Confirmatory factor analysis also implied that three underlying executive functions were clearly separable. Second, it is found that the roles of executive function and mental speed were variable in the model of cognitive aging, when different kinds of executive function and mental speed were chosen. Furthermore, the relations between mental speed and both age and other measures of cognition were enhanced, as measures of mental speed become more complex and comprising more executive components. These results indicated that the role of executive function (especially for memory updating) should be reconsidered in cognitive aging, as well as giving a beneficial supplement for processing speed theory.
The main findings of the ERP studies were that: First, in the condition of updating, an attenuated left posterior P250 and an enhanced anterior P300 effect were found when the serial position increased. Second, elderly participants had increased updating-related activity with an enhanced serial effect over frontal regions. In addition, the latency of P300 was prolonged in the elderly. Taken together, these results suggested that two mechanism (inhibitory and retrieval) were needed in memory updating processes, which consistent with interaction between prefrontal cortical areas of updating/retrieval processes and posterior cortical areas o.f stimulus temporal storage. Compare to younger participants, memory updating processes of older participants rely more on frontal resources.