Abstract
Debate persists regarding the nature of age-related deficits in inhibition, and whether inhibitory functioning depends on working memory systems. The current research aimed to measure age-related differences in inhibition and working memory, characterize the relationship between inhibitory functions and working memory performance, and determine how these relationships are affected by age. Toward these ends, we measured performance on a range of established paradigms in 60 young adults (18-30 years) and 60 older adults (60-88 years). Our findings support age-related increases in reflexive inhibition (based on the fixation offset effect and inhibition of return) and age-related decrements in volitional inhibition (based on several paradigms: antisaccade, Stroop, flanker, and Simon). This evidence of stronger reflexive inhibition combined with weaker volitional inhibition suggests that age-related deterioration of cortical structures may allow subcortical structures to operate less controlled. Regarding working memory, older adults had lower backward digit scores and lower forward and backward spatial scores. However, of the 32 analyses (16 in each age group) that tested for dependence of inhibitory functioning on working memory functioning, only one (in young adults) indicated that inhibition performance significantly depended on working memory performance. These results indicate that inhibition and working memory function largely independently in both age groups, and age-related working memory difficulties cannot account for age-related declines in inhibitory control.
This study indicates that, compared to young adults, older adults have difficulties with both working memory and volitional inhibition but show stronger reflexive inhibition.
The pattern of age differences shown in this study suggests that the balance of power shifts from cortical to subcortical brain structures as we age, which may reflect cortical brain regions deteriorating more rapidly as we age, thus limiting their ability to control subcortical brain regions.
In contrast to current theory, in this study the difficulties that older adults showed with volitional inhibition could not be explained by failing working memory systems, and both young and older adults showed very limited evidence that inhibitory functioning depends on working memory.