Understanding age-related reductions in visual working memory capacity: Examining the stages of change detection

Abstract

Visual working memory (VWM) capacity is reduced in older adults. Research has shown age-related impairments to VWM encoding, but aging is likely to affect multiple stages of VWM. In the present study, we recorded the event-related potentials (ERPs) of younger and older adults during VWM maintenance and retrieval. We measured encoding-stage processing with the P1 component, maintenance-stage processing with the contralateral delay activity (CDA), and retrieval-stage processing by comparing the activity for old and new items (old–new effect). Older adults showed lower behavioral capacity estimates (K) than did younger adults, but surprisingly, their P1 components and CDAs were comparable to those of younger adults. This remarkable dissociation between neural activity and behavior in the older adults indicated that the P1 and CDA did not accurately assess their VWM capacity. However, the neural activity evoked during VWM retrieval yielded results that helped clarify the age-related differences. During retrieval, younger adults showed early old–new effects in frontal and occipital areas and a late central–parietal old–new effect, whereas older adults showed a late right-lateralized parietal old–new effect. The younger adults’ early old–new effects strongly resembled an index of perceptual fluency, suggesting that perceptual implicit memory was activated. The activation of implicit memory could have facilitated the younger adults’ behavior, and the lack of these early effects in older adults may suggest that they have much lower-resolution memory than do younger adults. From these data, we speculated that younger and older adults store the same number of items in VWM, but that younger adults store a higher-resolution representation than do older adults.

Multimodal coding and strategic approach in young and older adults’ visual working memory performance

“…However, the challenge may not simply be related to a reduced visual working memory storage capacity per se. Using behavioural and ERP methods to investigate the encoding, maintenance, and retrieval stages of a color change detection task, Ko et al (2014) found that older adults appeared to engage the same sensory encoding processes, and store the same number of objects during maintenance, as young adults. However, older adults retained stimuli at a lower resolution.…”

The effect of cognitive training on the subjective perception of well-being in older adults

“…Even normally aging older adults experience significant impairment in attentional tasks (Getzmann, Golob & Wascher, 2016; Sperduti, Makowski & Piolino, 2016), episodic memory (Manenti et al, 2016; Tromp et al, 2015) and working memory tasks (Jost et al, 2011; Ko et al, 2014), time perception (Turgeon, Lustig & Meck, 2016) and also speed of processing (Ball et al, 2013; Elgamal, Roy & Sharratt, 2011). If poorly prevented, these impairments might degrade the quality of life as well as the psychological well-being (Pusswald et al, 2015; Stogmann et al, 2015).…”

ERP C250 shows the elderly (cognitively normal, Alzheimer’s disease) store more stimuli in short-term memory than Young Adults do

“…Also, other researchers using different paradigms have found similar positive activity with a comparable component (Begleiter, Porjesz and Wang, 1993) concerning working memory storage occurring over prefrontal and anterior areas in young adults (Ko et al, 2014). The sturdiness of this relationship leads us to utilize C250 as an index of storage in short-term memory that can be applied to other subject groups to study how short-term storage might vary with aging and cognitive conditions.…”

“…They attribute this effect to excessive attention to distracting information, which they supported with EEG spectral analysis of signals from frontal regions. Ko et al (2014) suggested that visual working memory capacity is reduced by aging, but the complexities of the entire memory storage, maintenance, and retrieval processes must be studied to unravel how this occurs. Also, Jost et al (2011) studied the contralateral delay activity of the EEG and determined that early in the retention interval older adults showed smaller filtering scores, which was indicative of retaining task-irrelevant information.…”