Exploring the impact of intensified multiple session tDCS over the left DLPFC on brain function

Abstract Multimodal interventions combining transcranial direct current stimulation (tDCS) with cognitive training have shown promise in producing lasting cognitive improvements among healthy aging individuals and patients with mild cognitive impairment (MCI). In this 5-day double-blind randomized trial, we investigated the effects of intensified tDCS protocol involving two trains of stimulation per day on working memory (WM) enhancement in 35 MCI patients. Specifically, we focused on the top-down attentional control aspect of WM and hypothesized that intensified tDCS would enhance performance on a visual object matching task (VOMT) immediately after the stimulation regimen and at a 1-month follow-up. Additionally, we explored whether the stimulation would augment online visual working memory (VWM) training. We also aimed to elucidate the neural mechanisms underlying these effects by analyzing fMRI activations during VOMT. Our findings suggest that intensified tDCS holds potential for enhancing WM in individuals with MCI, particularly in tasks involving top-down attentional control, as indicated by behavioral and neural observations. While the current study demonstrated support for an online and immediate impact of intensified tDCS, there were no long-lasting effects. Furthermore, the observed neural activations in the right insula may indicate that intensified tDCS induced immediate alterations in brain plasticity in MCI patients.