Holding On to the Past: Older Adults Show Lingering Neural Activation of No-Longer-Relevant Items in Working Memory

Abstract

Goal-relevant information can be maintained in working memory over a brief delay interval to guide an upcoming decision. There is also evidence suggesting the existence of a complementary process: namely, the ability to suppress information that is no longer relevant to ongoing task goals. Moreover, this ability to suppress or inhibit irrelevant information appears to decline with age. In this study, we compared younger and older adults undergoing fMRI on a working memory task designed to address whether the modulation of neural representations of relevant and no-longer-relevant items during a delay interval is related to age and overall task performance. Following from the theoretical predictions of the inhibitory deficit hypothesis of aging, we hypothesized that older adults would show higher activation of no-longer-relevant items during a retention delay compared to young adults and that higher activation of these no-longer-relevant items would predict worse recognition memory accuracy for relevant items. Our results support this prediction and more generally demonstrate the importance of goal-driven modulation of neural activity in successful STM maintenance. Furthermore, we showed that the largest age differences in the regulation of category-specific pattern activity during working memory maintenance were seen throughout the medial temporal lobe and prominently in the hippocampus, further establishing the importance of “long-term memory” retrieval mechanisms in the context of high-load STM tasks that place large demands on attentional selection mechanisms.

Effects of age on goal-dependent modulation of episodic memory retrieval

“…The concept of age deficits in inhibitory control has received much attention in the past, especially given the evidence that older adults' working memory performance is disproportionately impacted by the presence of distractors (for review see Lustig et al, 2007). This wealth of behavioral studies motivated recent fMRI research which employed working memory paradigms to demonstrate that older adults show less down-regulation of cortical activity in regions responsive to task-irrelevant stimuli (Chadick & Gazzaley, 2011;Chadick et al, 2014;Gazzaley et al, 2005Gazzaley et al, , 2008Weeks et al, 2020).…”

“…However, despite the wealth of behavioral studies examining age deficits in WM, neuroimaging evidence for the inhibitory deficit hypothesis is relatively sparse. Nonetheless, extant findings suggest that older adults demonstrate reduced ability to strategically downregulate cortical activity in regions selectively responsive to specific classes of perceptual information (Chadick & Gazzaley, 2011;Chadick et al, 2014;Gazzaley et al, 2005Gazzaley et al, , 2008Weeks et al, 2020). For example, Chadick et al (2014) reported that when participants were presented with overlapping images of a face and a scene in a delayed match to sample task, younger adults demonstrated attenuated activity in the parahippocampal cortex (relative to a 'no-task' baseline) when the scenes were task-irrelevant, and enhanced activity in the same region when they were task-relevant.…”

The influence of long-term memory on working memory: Age-differences in proactive facilitation and interference

“…In these cases, the interference may be occurring entirely within working memory, as information from previous trials has not been sufficiently removed or inhibited from active maintenance (see also Oberauer et al, 2017 ). Previous work has demonstrated that older adults are less efficient than younger adults at inhibiting no-longer-relevant information (Hasher et al, 2007 ; Lustig et al, 2001 ; Oberauer, 2001 , 2005 ; also, see Weeks et al, 2020 , for recent fMRI evidence of this), but whether or not previously learned information is more likely to interfere with older adults’ performance on a working memory task is, arguably, a separate issue. Oberauer et al ( 2017 ) also make this point about the wider literature where many instances of supposed interference from long-term memory in working memory tasks could instead be attributable to insufficient removal of information from working memory between trials.…”

Reduced Attentional Control in Older Adults Leads to Deficits in Flexible Prioritization of Visual Working Memory

“…Older adults' tendency to report the salient, but no longer relevant, cued item may reflect their lessened ability to inhibit previously attended information when it becomes task irrelevant, a process that is sometimes referred to as deletion or working memory updating [39,40,62,70,71]. In line with this proposal, older adults have recently been shown to display greater neural activation for no-longer-relevant items during working memory maintenance, an effect that predicts worse recall performance for relevant items [72]. Thus, older adults may have difficulty inhibiting irrelevant items especially when they were once assigned higher priority.…”