Effects of single/dual-target transcranial alternating current stimulation on working memory in healthy individuals

This study compared the effects of single- and dual-target high-definition transcranial alternating current stimulation(tACS) on working memory and explored the associated neural mechanisms using functional near-infrared spectroscopy(fNIRS). In a randomized, single-blind, sham-controlled design, 45 healthy participants received either dual-target stimulation, single-target stimulation, or sham stimulation, before and after which working memory performance was performed using n-back tasks with simultaneous fNIRS recording. Behavioral results showed that dual-target stimulation improved working memory performance, particularly under higher cognitive load, and yielded a greater proportion of responders when compared with sham stimulation, whereas single-target stimulation induced relatively limited effects. fNIRS findings indicated that dual-target stimulation modulated task-related cortical activation in prefrontal and temporal regions and enhanced both intra- and inter-hemispheric functional connectivity. Moreover, improvements in task accuracy were associated with strengthened functional connectivity within the frontoparietal and default mode networks. These findings suggest that dual-target tACS may be a promising strategy for enhancing working memory and highlight the importance of network-level modulation in cognitive enhancement.