Working memory and aging : cognitive processes

Normal aging, in absence of evidence of mild cognitive impairment (MCI) or dementia, is associated with a variety of changes in cognitive capacities, one of which is an overall decline in working memory performance. Importantly, information to be processed in working memory may be separated into distinct components including verbal, visual and spatial information, and, over the years, a number of experimental studies have reported evidence supporting the view that different types of information may be processed by different temporary storage systems. Accordingly, it is appropriate to evaluate whether age-related declines in working memory performance differ based on the type of information to be remembered. Indeed, previous studies have found that the age-related decline in working memory performance may differentially affect the maintenance of verbal, visual and spatial information.

It is important to note, however, that previous studies assessing visuo-spatial working memory in aging have utilized classical neuropsychological paradigms in which stimuli are presented on computer screens. They were thus limited to the assessment of egocentric spatial representations, which differ from allocentric spatial representations which are the type of spatial representations an individual may build when moving about in a real-world environment.

Our investigations into the allocentric spatial memory capacities of healthy young (20-30-years-old) and older (65-75-year-old) adults has shown that whereas older adults perform worse than young adults on both color and allocentric spatial memory tasks, their performance is particularly poor on working memory tasks. Some measures of performance suggest that spatial working memory may be more affected than color working memory. In contrast, other measures suggest that spatial and color working memory were equally affected. Altogether, our findings suggests that age-related declines in working memory may appear greater for spatial information because allocentric spatial memory may have quantitatively greater representational demands (i.e., require more bits of information) than color memory.