Background: Working memory, a fundamental short-term cognitive process, is known to decline with advanced age even in healthy older adults. Normal agerelated declines in working memory can cause loss of independence and decreased quality of life. Cognitive training has shown some potential at enhancing certain cognitive processes, although, enhancements are variable. Transcranial direct current stimulation (tDCS), a form of non-invasive brain stimulation, has shown promise at enhancing working memory abilities, and may further the benefits from cognitive training interventions. However, the neural mechanisms underlying tDCS brain-based enhancements remain unknown. Objective/Hypothesis: Assess the effects of a 2-week intervention of active-tDCS vs. sham paired with cognitive training on functional connectivity of the working memory network during an N-Back working memory task. Methods: Healthy older adults (N = 28; mean age = 74 ± 7.3) completed 10-sessions of cognitive training paired with active or sham-tDCS. Functional connectivity was evaluated at baseline and post-intervention during an N-Back task (2-Back vs. 0-Back). Results: Active-tDCS vs. sham demonstrated a significant increase in connectivity between the left dorsolateral prefrontal cortex and right inferior parietal lobule at postintervention during 2-Back. Target accuracy on 2-Back was significantly improved for active vs. sham at post-intervention. Conclusion: These results suggest pairing tDCS with cognitive training enhances functional connectivity and working memory performance in older adults, and thus may hold promise as a method for remediating age-related cognitive decline. Future studies evaluating optimal dose and long-term effects of tDCS on brain function will help to maximize potential clinical impacts of tDCS paired with cognitive training in older adults.

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The impact of cognitive aging on brain function and structure is complex, and the relationship between aging-related structural changes and cognitive function are not fully understood. Physiological and pathological changes to the aging brain are highly variable, making it difficult to estimate a cognitive trajectory with which to monitor the conversion to cognitive decline. Beyond the information on the structural and functional consequences of cognitive aging gained from brain imaging and neuropsychological studies, non-invasive brain stimulation techniques such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) can enable stimulation of the human brain in vivo, offering useful insights into the functional integrity of intracortical circuits using electrophysiology and neuromodulation. TMS measurements can be used to identify and monitor changes in cortical reactivity, the integrity of inhibitory and excitatory intracortical circuits, the mechanisms of long-term potentiation (LTP)/depression-like plasticity and central cholinergic function. Repetitive TMS and tDCS can be used to modulate neuronal excitability and enhance cortical function, and thus offer a potential means to slow or reverse cognitive decline. This review will summarize and critically appraise relevant literature regarding the use of TMS and tDCS to probe cortical areas affected by the aging brain, and as potential therapeutic tools to improve cognitive function in the aging population. Challenges arising from intra-individual differences, limited reproducibility, and methodological differences will be discussed.

Aim. Rasmussen encephalitis is associated with severe seizures that are unresponsive to antiepileptic drugs, as well as immunosuppressants. Transcranial direct current stimulation (t‐DCS) is a non‐invasive and safe method tried mostly for focal epilepsies with different aetiologies. To date, there is only one published study with two case reports describing the effect of t‐DCS in Rasmussen encephalitis. Our aim was to investigate the effect of t‐DCS on seizures in Rasmussen encephalitis and to clarify its safety. Methods. Five patients (mean age: 19; three females), diagnosed with Rasmussen encephalitis were included in this study. Patients received first cathodal, then anodal (2 mA for 30 minutes on three consecutive days for non‐sham stimulations), and finally sham stimulation with two‐month intervals, respectively. Three patients received classic (DC) cathodal t‐DCS whereas two patients received cathodal stimulation with amplitude modulation at 12 Hz. Afterwards, all patients received anodal stimulation with amplitude modulation at 12 Hz. In the last part of the trial, sham stimulation (a 60‐second stimulation with gradually decreasing amplitude to zero in the last 15 seconds) was applied to three patients. Maximum current density was 571 mA/m2 using 70 mm × 50 mm wet sponge electrodes with 2‐mA maximum, current controlled stimulator, and maximum charge density was 1028 C/m2 for a 30‐minute stimulation period. Results. After cathodal stimulation, all but one patient had a greater than 50% decrease in seizure frequency. Two patients who received modulated cathodal t‐DCS had better results. The longest positive effect lasted for one month. A second trial with modulated anodal stimulation and a third with sham stimulation were not effective. No adverse effect was reported with all types of stimulations. Conclusion. Both classic and modulated cathodal t‐DCS may be suitable alternative methods for improving seizure outcome in Rasmussen encephalitis patients.