Enhancing verbal working memory by focalized tDCS

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Verbal working memory, the temporary maintenance of verbal information, is a key capacity of human cognition which is particularly relevant for successful and efficient every-day communication. This faculty is often affected by normal aging and in neurological and psychiatric disorders. The planned project will investigate the neural mechanisms and predictors underlying enhancement of verbal working memory by individualized, focal transcranial direct current stimulation (tDCS). To this end, we will combine individualized tDCS with a well-established n-back paradigm in healthy volunteers. We will complement univariate functional neuroimaging analyses with advanced functional and effective connectivity measures as well as graph theoretical approaches to map stimulation induced changes at the neural network level and relate them to behavioral changes. A better understanding of the neural underpinnings of modulatory tDCS effects on verbal working memory function will help to refine current models of verbal working memory and ultimately increase treatment efficacy of neurostimulation protocols in individuals with verbal working memory deficits.Within the broader context of the Research Unit (RU), the present study is one of eight projects investigating tDCS effects on learning and memory formation across functional domains (Projects 1-8) and the healthy human lifespan. The highly systematic and coordinated approach pursued by these empirical projects will allow for the first time analyzing the underlying neural mechanisms and predictors of behavioural stimulation response not only within each project, but also across the different tasks and functional domains (in Project 9).The current project will contribute unique information on how tDCS modulates verbal working memory, thereby complementing the investigation of tDCS-induced enhancement of verbal episodic memory formation in Project 3 (PI Meinzer). Collectively, the results of the empirical projects of the RU will increase our current understanding of tDCS-induced neural network effects, their regional specificity, the mechanisms underlying inter-individual variability of stimulation effects, and potential changes due to chronological age. From a methodological point of view, data acquired in these projects will contribute to optimizing and validating biophysical models of current flow (in P9+10), thereby advancing future experimental and translational applications of tDCS in health and disease.