Neuronal and behavioral effects of multi-day brain stimulation and memory training.

Strategies for memory enhancement, especially for the older population, are of great scientific and public interest. Here, we aimed at investigating neuronal and behavioral effects of transcranial direct current stimulation (tDCS) paired with memory training. Young and older adults were trained on an object-location-memory task on 3 consecutive days with either anodal or sham tDCS. Recall performance was assessed immediately after training, 1 day and 1 month later, as well as performance on trained function and transfer task. Resting-state functional magnetic resonance imaging was conducted at baseline and at 1-day follow-up to analyze functional coupling in the default mode network. Anodal tDCS led to superior recall performance after training, an associated increase in default mode network strength and enhanced trained function and transfer after 1 month. Our findings suggest that tDCS-accompanied multi-day training improves performance on trained material, is associated with beneficial memory network alterations, and transfers to other memory tasks. Our study provides insight into tDCS-induced behavioral and neuronal alterations and will help to develop interventions against age-related cognitive decline.