Age Related Changes During Adulthood in Cognitive Processes Reliant on the Pre-Frontal Cortex: Attention, Inhibitory Control, Working Memory and Relational Processing

Abstract

The frontal lobe hypothesis of ageing proposes that cognitive functions associated with the prefrontal cortex (PFC) are more susceptible to age-related changes than those supported by other brain regions (e.g., Dempster, 1992; West, 1996). Age-related declines previously demonstrated in working memory (e.g., Bopp & Verhaeghen, 2005), inhibitory control (Dempster, 1992), executive attention (e.g., West, 2004) and fluid intelligence (Horn & Cattell, 1967), have been linked to changes in PFC functioning. Relational processing also depends on the integrity of the PFC (e.g., Christoff et al., 2001), but research on age-related declines in relational processing is limited (Andrews & Todd, 2008; Viskontas, Holyoak, & Knowlton, 2005; Viskontas, Morrison, Holyoak, Hummel, & Knowlton, 2004). Unlike previous research which tended to focus on a single construct, the current research investigated age-related changes in executive attention, inhibitory control, working memory and relational processing. Distinctions within three constructs were also of interest. Three aspects of inhibitory control (response inhibition, task-set switching and inhibition in memory retrieval) were examined. Relational processing was examined in four tasks, three of which involved items at two or more levels of complexity. Working memory was examined using simple span and complex span tasks. The test battery of 16 tasks assessed these constructs as well as speed of processing, crystallized and fluid intelligence, and frontal functioning (Tower of London). It was administered to a sample of 125 normally ageing adults who ranged in age from 18 years to 92 years with all age decades represented.