Optimizing tACS for working memory: differential outcomes in healthy aging and non-amnestic mild cognitive impairment
Abstract
Transcranial alternating current stimulation (tACS) in the theta frequency range has been shown to enhance working memory (WM) performance. However, no studies have directly compared the effects of theta tACS between cognitively healthy elderly (HE) subjects and subjects with non-amnestic mild cognitive impairment (MCI). Our proof-of-concept study investigated the effects of monofocal (frontal) and bifocal (frontoparietal) theta tACS on WM in two cognitive loads in HE subjects and in subjects with MCI. In this sham-controlled, single-blinded, repeated-measures study with counterbalanced stimulation order across subjects (n = 55), theta tACS (4.51 Hz, 1.5 mA, 20 min) was applied either over the frontal site alone or simultaneously over frontal and parietal sites. WM 2-back and 3-back tasks were performed during and after each stimulation session. In the HE group, both frontal and frontoparietal stimulations improved performance, albeit with load-dependent differences. Frontal stimulation was particularly effective in the higher cognitive load, enhancing accuracy (β = -3.87; p = .033) and reaction times (β = - .042; p = .002) in the 3-back task. Frontoparietal stimulation improved accuracy (β = -3.74; p = .027) but not reaction time (p > .22) in the 2-back task in the HE group. Frontoparietal stimulation enhanced accuracy in the 3-back task across all participants (β = 1.91; p = .043). In the MCI group, frontal stimulation led to faster reaction times in the 3-back task,…
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 55 participants or records.
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