Are Old Adults Just Like Low Working Memory Young Adults? Filtering Efficiency and Age Differences in Visual Working Memory

Abstract

While it is well known that working memory functions decline with age, the functional reasons for this decline are not well understood. A factor that has proven critical for general individual differences in visual working memory capacity is the efficiency of filtering irrelevant information. Here, we examine to what degree this factor is also responsible for age differences in working memory. Young and old participants performed a change-detection task where some items in the encoding display were marked as irrelevant. The contralateral delay activity of the electroencephalogram was used to assess individual participants' filtering efficiency (see Vogel EK, McCollough AW, Machizawa MG. 2005. Neural measures reveal individual differences in controlling access to working memory. Nature. 438:500-503.). Older adults showed smaller filtering scores than young adults, but only early in the retention interval, suggesting that efficient filtering was delayed. In contrast, age-independent individual differences in filtering were reflected primarily later in the retention interval. Thus, age and individual differences in filtering are reflected in different ways showing that old adults are not simply like less efficiently performing young adults.

Working memory, long-term memory, and medial temporal lobe function

“…Typically, such a group has a mean age .60 years and, on average, ,16 years of education. Memory capacity is smaller for older adults than for undergraduate students (Jost et al 2011). Furthermore, estimates of visual working memory capacity in change-detection tasks are typically obtained by assessing performance after delays of 1 sec (e.g., 900 msec in Luck and Vogel 1997; average delay of 1.1 sec [average of 300, 900, and 2000 msec] in Eng et al 2005), and therefore do not provide suitable estimates of working memory capacity in tests given after delays of 4 sec or longer (as in the studies of Nichols et al 2006;Olson et al 2006a).…”

Inter-individual performance differences in younger and older adults differentially relate to amplitude modulations and phase stability of oscillations controlling working memory contents

“…This theoretical proposition is supported by recent studies that observed a selective age deficit in the NeuroImage 60 (2012) [71][72][73][74][75][76][77][78][79][80][81][82] suppression of irrelevant information in particular during early stages of WM encoding (Gazzaley et al, , 2008. These studies suggest that inhibitory control of WM contents may not be disabled completely in older adults, but rather delayed in time (Jost et al, 2011;Zanto et al, 2010). In addition, the robustness of inhibitory mechanisms depends on the task difficulty and the individual performance level.…”

Age-related changes in working memory and the ability to ignore distraction

“…A specific impairment in suppressing distractor representations in older adults has been linked to reduced WMC (5). Typically distractors are presented either with the items to be remembered (encoding distraction, ED, e.g., 6,7) or while these items are held in mind (delay distraction, DD, e.g., 5,8). We recently highlighted a distinction between the effects of these two types of distraction in younger adults (9).…”

“…Here we examine the well-known age-related reduction in WMC. Previous work has identified an age-related delay in ED filtering (7) and an early age-related deficit in DD suppression (8). We directly compare the age-related decline in ED and DD to assess whether an ability to ignore a distraction at encoding or at delay provides the best predictor of general WMC.…”