Working memory training in older adults: Load- and phase-dependent changes in brain activation

It has been demonstrated that cognitive training can improve working memory task performance in older adults; however, less is known about the associated brain changes. This study examines how brain activation changes in older adults as a function of working memory training improvement and how this relationship is influenced by task load and training phase. Participants were 58 cognitively healthy older and 28 younger adults from the Attentional Control Training for Older People (ACTOP) study. Older participants completed either working memory training or an active control condition (inhibition training) and received fMRI scans while completing an N-back task at low (1-back) and high (2-back) load before training (PRE), after 6 (MID) and 12 (POST) training sessions. Younger participants served as an age comparison for brain activation. Working memory training improvement was associated with an early (PRE to MID) decrease in activity in frontoparietal regions during the 1-back condition, followed by a late-phase (MID to POST) increase in activity in the frontal lobe during the 2-back condition. There were no significant associations in the control group. Furthermore, there was a significant difference in load-related activation (2>1 back) between older and younger adults at PRE, which was no longer observed at POST within the medial and left hemisphere, suggesting that training restores older adults' load-related modulation of activation to more youthlike levels. These results suggest that working memory training gain in older adults is associated with more efficient brain activation for low-load tasks and a greater ability to recruit neural resources as tasks become more demanding.