Enhancing cerebellar-dependent motor learning by focalized tDCS

• Applicant: Professorin Dr. Dagmar Timmann-Braun
• Subject Area: Human Cognitive and Systems Neuroscience
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 467143400

There is significant interest to use cerebellar transcranial direct current stimulation (cerebellar tDCS) as a tool to understand cerebellar function and to treat cerebellar disease. Cerebellar tDCS effects, however, are often difficult to replicate even within the same laboratory, indicating considerable variability between individual participants and hampering more widespread use. The aim of the present project is to test whether focalized tDCS based on the individual cerebellar anatomy reliably enhances cerebellar-dependent motor learning, to understand the neuronal mechanisms underlying focalized cerebellar tDCS effects and to identify the predictors of individual cerebellar tDCS effects in a highly systematic and comprehensive manner. We will use eyeblink conditioning to study cerebellar tDCS effects on motor learning because it is strongly cerebellar-dependent and the associated cerebellar areas are well known. Furthermore, the ability to acquire conditioned eyeblink responses declines with increasing age and is impeded by cerebellar disease. Importantly, the initially described enhancing effects of anodal cerebellar tDCS on the acquisition of conditioned eyeblink responses were difficult to replicate in later studies. Therefore, eyeblink conditioning is an excellent model to optimize cerebellar stimulation protocols on an individual level in order to increase efficacy of the intervention, and to better understand possible predictors of cerebellar tDCS effects on motor learning in individual participants.Within the broader context of the RU, the present study (Project 6) 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 behavioral stimulation response not only within each project, but also across the different tasks and functional domains (in Project 9). The current project will complement the investigation of tDCS-induced enhancement of motor sequence learning in Project 5 that also investigates behavioral and neural modulation of individualized, focal tDCS in the motor domain, but with the primary motor cortex as the relevant hub in this paradigm. 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 Projects 9+10), thereby advancing future experimental and translational applications of tDCS in health and disease.

• DFG Programme: Research Units
• Subproject of: FOR 5429: Modulation of brain networks for memory and learning by transcranial electrical brain stimulation: A systematic, lifespan approach
• International Connection: Israel
• Cooperation Partner: Professor Dr. Opher Donchin
• Co-Investigator: Dr.-Ing. Andreas Deistung