Transcranial direct current stimulation selectively improves temporal working memory

Abstract

Temporal working memory (WM)—the ability to temporarily store and manipulate temporal information—is constrained by a storage capacity threshold of approximately 2–3 s. Transcranial direct current stimulation (tDCS), an emerging non-invasive intervention, holds potential for enhancing temporal WM. We investigated whether anodal tDCS over key WM regions (right prefrontal cortex, PFC; posterior parietal cortex, PPC) could improve temporal WM capacity specifically for durations exceeding the critical threshold. We used a matching-to-sample paradigm with sample durations encompassing the threshold (1, 2, 3, 4 s); improvement in temporal WM capacity was operationally defined specifically as enhanced accuracy for supra-threshold durations (3 and 4 s). Fifty-six healthy participants were randomly assigned to receive either actual or sham stimulation over PFC or PPC, and completed the matching-to-sample task once before and once immediately after stimulation. Results showed that anodal stimulation over the PFC selectively enhanced performance at the 3 s duration, with no significant effects at other durations or with PPC stimulation. These findings provide causal evidence underscoring the crucial role of the PFC—rather than the PPC—in supporting temporal WM, with the effect of the single-session tDCS protocol being specific to the 3 s duration, which represents the critical threshold point.