Tan, Davynn G.H.Davynn G.H.TanFu, Yvette YumiaoYvette YumiaoFuDr. LAM Lok-hang, TommyTommyDr. LAM Lok-hangChin, Hiu FunHiu FunChinLi, Charmaine K.Y.Charmaine K.Y.LiTsui, Winky W.K.Winky W.K.Tsui2026-09-052026-09-052025Tan, D. G. H., et al. (2025). Effect of HD-tDCS on ageing working memory: Practice-dependent influence. In Brain Stimulation, vol. 18(1). 6th International Brain Stimulation Conference, Kobe, Japan (pp. 376). Elsevier BV.1935-861X1876-4754http://hdl.handle.net/20.500.11861/29073Open accessIntroduction: High-definition transcranial current stimulation (HD-tDCS) shows promise for improving ageing working memory. However, prior task activity may affect the HD-tDCS after-effect according to the activity-dependent model [1]. This preliminary study investigated the practice-dependent effects of HD-tDCS on working memory in healthy older adults.<br> Methods: Ten healthy older adults (7 male) with a mean age of 64.6 ± 2.1 years were recruited and received 10 minutes of either 2mA anodal or sham HD-tDCS to the left dorsolateral prefrontal cortex over 2 sessions that were one week apart. One block of two-back task was performed before and after the stimulation in every session with each block consisting of 200 trials. Participants in the less-practice group (n=6) received anodal stimulation with less task experience (1 task block before stimulation) whereas those in more-practice group (n=4) received anodal stimulation with more task experience (3 task blocks before stimulation). Two-way ANOVA was conducted on the behavioural measure (change in d-prime, or Δd’) and the amplitude change in event-related potentials (ERPs) N200 and P300. Results: Significant interaction between stimulation (anodal vs. sham) and prior practice (less vs more) revealed that individuals with less prior practice had greater Δd’ (F(1,8)=21.310, p=.002) and greater ΔN200 amplitude at left frontal area (F(1,8)=7.642, p=.025) after anodal HD-tDCS relative to more-practice group (p=.008), as well as compared to after sham stimulation (p=.008). A greater ΔN200 amplitude at the left frontal region for target trials after anodal stimulation was found to be positively correlated with enhanced task performance (r=0.627, p=.052). Discussion/Conclusion: The pilot findings suggest that less prior practice amplifies the beneficial effects of HD-tDCS, potentially due to the brain's regulatory mechanisms adjusting plasticity thresholds based on previous activities, or meta-plasticity. This has important implications for the design of tDCS/HD-tDCS research and clinical application.enHD-TDCSActivity-DependentWorking MemoryAgeingConference Paper10.1016/j.brs.2024.12.483