Investigation of a Model-Based Working Memory Training With and Without Distractor Inhibition and Its Comparative Efficacy: A Randomized Controlled Trial on Healthy Old Adults.

: Various working memory (WM) trainings have been tested, but differences in experimental designs, the lack of theoretical background, and the need of identifying task-related processes such as filtering efficiency limit conclusions about their comparative efficacy. : In this study, we compared the efficacy of a model-based WM training with (MB) and without (MB) distractor inhibition on improving WM capacity to a dual and active control condition. : This randomized clinical trial included 123 healthy elderly adults (78 women, 45 men; aged 64.1 ± 8.3 years). All groups underwent 12 40-min training sessions over 3 weeks and four cognitive testing sessions. The first two sessions served as double baseline to account for practice effects. Primary outcome was WM capacity post-training measured by complex span tasks. Near and far transfer was assessed by simple span, n-back, visuospatial and verbal learning, processing speed, and reasoning tasks. : Due to preliminary termination (COVID-19), 93 subjects completed the post-training and 60 subjects the follow-up session. On a whole group level, practice effects occurred from prebaseline to baseline in WM capacity ( = 4.85, = 4.01, < 0.001, = 0.37). Linear mixed-effects models revealed a difference in WM capacity post-training between MB and MB ( = -9.62, = -2.52, = 0.014, = 0.27) and a trend difference between MB and dual ( = -7.59, = -1.87, = 0.065, = 0.20) and control training ( = -7.08, = -1.86, = 0.067, = 0.20). Univariate analyses showed an increase between pre- and post-training for WM capacity within MB ( = -3.34, < 0.05) only. There was no difference between groups pre- and post-training regarding near and far transfer. Univariate analyses showed improved visuospatial learning within MB ( = -3.8, < 0.05), improved processing speed ( = 2.19, < 0.05) and -back performance ( = 2.12, < 0.05) in MB, and improved -back performance ( = 3.83, < 0.001) in the dual -back training. : A model-based WM training including filtering efficacy may be a promising approach to increase WM capacity and needs further investigation in randomized controlled studies.