Age-related differences in working memory subprocesses decomposed by the reference-back paradigm

We used a data-driven approach to study the electrophysiological correlates of the working memory subprocesses revealed by the reference-back paradigm. In the absence of prior research, we focused on how aging affects the four subprocesses: updating, substitution, gate opening, and gate closing. We conducted our experiment with 25 younger adults (M=20.17{+/-}1.47) and 23 older adults (M=67.35{+/-}4.01) using the reference-back paradigm. Significant reaction time costs were observed for all four subprocesses, but age-related differences were found only in substitution, which was larger in older than younger adults, indicating it as being the most vulnerable subprocess in aging. Using difference waves, we identified event-related potential components that characterize the subprocesses we studied. Regarding updating: three occipital negativities between 80-180 ms, 300-400 ms, and 400-1,000 ms were observed, with only the latter range showing age group differences. Source analysis showed larger activity differences in the right frontal and temporal areas for younger adults. Regarding substitution: a frontal positivity between 250-600 ms emerged in younger adults, while a posterior positivity between 550-750 ms was found in older adults indicating different underlying processes supported by sLORETA results. Regarding gate opening: three parieto-occipital components were identified: a negativity between 150-250 ms, a positivity between 300-500 ms, and a positivity between 500-700 ms, all showing age-related differences. Regarding gate closing: we found an occipital negativity between 150-300 ms and a frontal positivity between 300-600 ms, neither of which changed between the age groups. From our findings, we conclude that the process of protecting information (gate closing) remains stable with age, despite older adults sensitivity to interference. Conversely, gate opening is sensitive to age-related changes, likely to be resulting in different brain activity patterns during substitution being the updating of working memory with new information.