Transcranial direct current stimulation (tDCS) in cognitively symptomatic older adults

Background tDCS offers an inexpensive, portable, well‐tolerated, and safe approach to neuromodulation. These benefits led to a rapid increase in its use as a potential treatment for those with Alzheimer’s disease and related dementias (ADRD), yet were accompanied by a number of methodological gaps that limit its current translational potential. This session will introduce and evaluate several such methodological factors including potential mechanisms of action, dose‐response relationships, session frequency and duration, and individual factors that may account for variable treatment response. Method Data from over 300 participants across the ADRD spectrum and 2,500 tDCS sessions who were enrolled at the Research Program on Cognition and Neuromodulation Based Interventions will be used to demonstrate the potential impact of the above noted methodological factors. Structural and functional neuroimaging data will be included to demonstrate both theoretical and empirical effects of tDCS. Result Across studies, our results demonstrate that targeted, multi‐electrode tDCS can alter underlying neurotransmitter levels and potentially “normalize” patterns of “activation” and functional connectivity in those with cognitive impairment. However, there is remarkable variability in the amount of electrical current delivered to the brain across participants (>600%) as well as the targeted brain region, which require reconsideration of the traditional dosing at the scalp approach. Moreover, there are apparent polarity‐dependent effects as well as differences between passive versus active (i.e., cognitive task performance) measurements. Ongoing work evaluates the additional impact and nature of disease pathology on these factors. Conclusion The combination of results highlights the complex and multifaceted nature of tDCS and may translate to other forms of neuromodulation.