| The particular vulnerability of the prefrontal cortex to age-related deterioration has been frequently posited as an explanation for functional decline in aging. West's (1996) prefrontal cortex function theory of cognitive aging maintains that age-related decline in cognitive processes supported by the prefrontal cortex emerge at an earlier age and are of greater magnitude than age-related declines observed in cognitive processes supported by nonfrontal regions. In this study, four specific processes underlying prefrontal cortex function (prospective memory, retrospective memory, interference control, and inhibitory control) were theorized to account for age-related declines in a number of cognitive functions, including verbal memory. This study investigated to what extent these four prefrontal cortex processes were discernable and the mediating role they played between age and verbal memory. One hundred nine healthy older adults, aged 55–88 years, completed multiple performance measures thought to evaluate prefrontal cortex function, verbal memory, and depression. Exploratory factor analyses indicated a two-factor model of prefrontal cortex function that was only marginally consistent with West's proposed model. These two factors were: (1) a factor containing measures of interference control, sustained attention, processing speed, and inhibitory control; and (2) a working memory factor. Structural equation modeling analyses indicated that this two-factor measurement model strongly mediated the relationship between age and verbal memory performance. Verbal memory performance decreased as a result of poorer prefrontal cortex function performance with older age. Results suggested that despite difficulties in the specific and selective measurement of prefrontal cortex function, there is strong support for the hypothesis that cognitive aging is highly dependent on the integrity of prefrontal cortex functions. |
