Neuromodulation of Working Memory: Mechanisms, Targets, and Behavioral Outcomes

Working memory (WM) is a capacity-limited control system that maintains and updates task-relevant representations for goal-directed cognition. Because WM declines with aging and is disrupted across neuropsychiatric and neurodegenerative disorders, neuromodulation has emerged as both a causal probe of circuit function and a potential therapeutic adjunct. This mechanistic narrative review evaluates evidence across transcranial direct current stimulation, transcranial magnetic stimulation/theta-burst stimulation, transcranial alternating current stimulation, transcranial random noise stimulation, and deep brain stimulation. Rather than asking whether neuromodulation uniformly enhances WM, we examine when different modalities alter distinct WM subprocesses. Across modalities, effects are generally modest and heterogeneous, but the literature increasingly suggests that stimulation acts less by adding "capacity" than by biasing gain, timing, and plasticity-related control variables that shape WM trajectories. More precise dosing, targeting, and computation-aligned outcomes are needed to establish reproducible and mechanistically interpretable effects.