Optimization of focal brain stimulation by individualized electric field simulations: Implementation and assessment of effects across sites and functional domains

点击翻译按钮获取中文摘要

Advanced computational modeling approaches have been developed to estimate the strength and distribution of the electric field induced by brain stimulation. By using magnetic resonance imaging (MRI) based head models, these approaches allow individualized simulations of current flow. Previous studies have revealed considerable inter-individual variability in the strength and distribution of the electric field induced in the brain and have linked it to the variability of the stimulation outcome. Similarly, functional and microstructural properties of the stimulation targets were linked to variable stimulation effects. However, the predictive value of individually induced electric fields in the human brain for behavioral and neurophysiological stimulation outcomes and their variability still needs to be established. Additionally, while methods for tDCS current flow optimization are being developed, current knowledge about dose-response relationships is rudimentary and little is known about potential differences between cortical areas, functional domains, changes across the healthy human lifespan and other modulating factors. This will be addressed for the first time by the highly coordinated and optimized stimulation approach implemented in the Research Unit (RU).To meet these challenges, Project 9 (P9) of the RU will (A) fulfill a service function for the empirical projects (P1-8) by providing the methodology required for a reliable personalized targeting. Based on structural MRI data acquired in the empirical projects, we will develop an individualized and focal stimulation approach to enable optimized and coordinated stimulation protocols in P1-8 of the RU. Further, we will complement research in these individual projects by examining sources of variability in behavioral and neural tDCS responses using a hypothesis-driven approach within and across projects: (B.1) collaborating with P1-8 to determine the effect of simulated electric fields on behavioral and neuronal outcomes in a domain specific way (within projects), and (B.2) investigating cross-project consistency of the effects, thereby leveraging the unique large and coordinated dataset that will be acquired by the RU, to assess the relationship between inter-individual variability in electric fields and stimulation effects across brain sites and functional domains. In the long run, this project will enable future studies to systematically plan and implement individually optimized tDCS interventions. Moreover, the potential second phase of the RU will explore how age-associated brain changes impact cortical-dose relationships as well as their mediators. Therefore, the results of the project will lay the foundation for individually optimized stimulation protocols across the human lifespan, with the ultimate goal to optimize stimulation outcome for the individual.