Cognitive enhancement through non-invasive brain stimulation has gained increasing attention, yet findings remain heterogeneous and often inconsistent. A key challenge is to disentangle genuine stimulation effects from practice or placebo-related improvements.

The present study investigates whether transcranial alternating current stimulation (tACS) in the individual theta range (4–7 Hz) enhances verbal working memory capacity. We employ a single-blind, within-subjects crossover design (N = 20) using the Running Span Task, a demanding paradigm shown to be largely resistant to unspecific training effects. Individual theta frequency is estimated from resting-state EEG, and participants complete active and control sessions while performing the task before and during stimulation.

Building on theoretical accounts linking slower theta oscillations to greater working-memory capacity via more efficient theta–gamma coupling, we test whether frontoparietal theta-tACS can improve verbal maintenance performance. Data collection is ongoing; preliminary results and implications for models of neural oscillatory mechanisms in working memory will be discussed.