Effects of online prefrontal transcranial alternating current stimulation in the alpha and theta frequency bands on...

Executive functions (EFs) are high-level cognitive processes essential for adaptive, goal-directed behavior. They are supported by oscillatory neural activity, particularly in the alpha and theta frequency bands, across local and distributed brain networks involving prefrontal regions. Previous studies have used transcranial alternating current stimulation (tACS) to modulate such activity and have reported significant performance improvement on EF tasks. However, most relied on single-task scores as outcome measures, which may reflect not only domain-general executive functioning but also task-specific or lower-level processes. This double-blind sham-controlled within-subject study examined the effects of online prefrontal tACS at alpha (10 Hz) and theta (6 Hz) frequencies on EF performance, measured via latent-variable scores that capture shared variance across multiple EF tasks, in healthy individuals (n = 24). Outcome measures were derived using the NIH EXAMINER battery, yielding latent scores for four EF components (common EF, cognitive control, working memory, and fluency) as well as task scores. Linear mixed models revealed significantly higher common EF and cognitive control scores during alpha-tACS, with large effect sizes, and smaller, more limited stimulation effects on task scores. Exploratory analyses suggested biological sex-specific response to stimulation, with alpha-tACS effects observed primarily in females. These findings support a causal role for prefrontal alpha-band oscillations in EFs and underscore the value of latent-variable measures of executive functioning in neuromodulation research.