Modulating the motor system with tDCS to enhance post-stroke motor recovery mentored by Sook Lei Lieu, Ph.D. and Danny JJ Wang, Ph.D.
Stephanie Lefebvre is a Postdoctoral Researcher at USC’s Neural Plasticity and Neurorehabilitation Laboratory. Prior to this position, she completed a B.S. in Genetics and Biology from the UCBL (France), a MSc, in Biomedical Sciences from the UNIL (Switzerland), and a Ph.D. in Biomedical Sciences from the UCL (Belgium). She also completed a first Postdoctoral Fellowship at the University of Lille (France) and a second one at the CNRS, Lyon (France). Her main research interest is to promote the use of noninvasive brain stimulation to modulate neural plasticity to restore brain function after neurological disease.
In her previous work, she used transcranial direct stimulation (tDCS) to enhance motor skill learning and motor recovery in stroke patients. This work led to several publications in high-impact factor journals such as Brain (Lefebvre et al., 2014). However, according to recent meta-analyses, post-stroke motor improvements from tDCS are limited by substantial inter-individual variability (Lefebvre and Liew, 2017). A major issue limiting the use of tDCS in post-stroke recovery is the lack of understanding of how exactly tDCS works in the post-stroke brain to improve recovery. Studies have shown that tDCS not only modulates the local brain regions being stimulated but also global whole-brain networks (for a review, see Liew et al., 2014). Better understanding how tDCS affects the motor network in individuals after stroke could provide critical insight into how to maximize this promising technology for rehabilitation.
The present project focuses on determining the ideal tDCS parameters to enhance the reliability of tDCS in stroke recovery. Dr Lefebvre’s proposal includes a two-part experiment using both tDCS alone and simultaneous tDCS-fMRI to map the effects of tDCS on global brain networks in healthy individuals and individuals after stroke. In the first part, she proposes to examine the effects of tDCS on different neural targets on motor performance in individuals with chronic stroke and age-matched healthy adults. Specifically, tDCS will be applied over different neural targets (the primary motor area, and the premotor cortex). The impact of tDCS on motor learning will be compared between these proposed neural targets and groups (stroke, age-matched controls). Then, in a separate session with a subset of the same individuals, she proposes to perform a simultaneous tDCS-fMRI session in order to understand the effects of tDCS over these different neural targets on whole-brain network connectivity. The MRI session will also include diffusion MRI (structural connectivity), resting state fMRI (functional connectivity) and task-based fMRI (diffuse brain activity) to better understand how an individual’s structural and functional brain connectivity might predict the effects of tDCS.
Overall, this project will provide critical pilot data to support experiments looking at: 1) a determination of which neural targets will have the best potential in improving post-stroke motor recovery, 2) a better understanding of the mechanisms of action of tDCS on whole brain networks after stroke, and 3) the potential identification of robust biomarkers that can predict tDCS responsiveness across individuals.