Understanding the neural mechanism by which neurostimulation drives visual working memory: An inside view of neurostimulation decay
Hector Arciniega1, Marian Berryhill1; 1University of Nevada, Reno,
Working memory (WM) permits the maintenance of information over brief delays and is an essential executive function. Unfortunately, WM performance declines with age. Some evidence indicates that pairing WM tasks with transcranial direct current stimulation (tDCS) improves WM in some participant populations after a single session. Yet, the neural mechanism(s) by which tDCS elicits these effects are poorly understood. Here, we tested two tDCS montages that we previously applied to healthy older adults, and included offline HD-EEG. We sought to clarify the neural mechanism by which different tDCS montages improved WM performance in participant subgroups. The first montage targeted right prefrontal cortex and posterior parietal sites (anode PFC- cathode PPC). Previously, this montage selectively improved WM performance in low WM capacity older participants. The second montage was right PFC alone (anode PFC – cathode contralateral cheek). Highly educated older adults showed WM benefit using this montage in previous work. Participants completed 3 counterbalanced sessions (PFC-PPC, PFC, sham; 20 minutes, 2 mA). After tDCS, participants performed a visual WM task while HD-EEG data was collected. Older adults with more education showed a tDCS-linked WM benefit after either tDCS montage compared to sham tDCS. However, the results revealed that behavioral effects dissipated quickly (~12 minutes). This made HD-EEG data analysis underpowered. We confirm that group differences are essential to consider in tDCS studies of WM. The quickly decaying effects prevented further clarification of mechanism from the HD-EEG data.
Topic Area: EXECUTIVE PROCESSES: Working memory