Individualizing Transcranial Direct Current Stimulation to improve motor learning in stroke
Transcranial Direct Current Stimulation (tDCS) is an innovative treatment modality in which a small current is applied to the brain using surface electrodes. It has been shown to enhance motor learning in healthy subjects and stroke patients and is therefore considered a potential new clinical tool for rehabilitation after stroke. However, even though several studies in sub-acute and chronic stroke patients have shown highly promising results, other studies did not show added value of tDCS. The inconsistent results may largely be due to a lack of mechanistic understanding and tools to target tDCS to the individual patient.
The goal of the i-tDCS project is to develop monitoring tools of individual functional brain organisation of stroke patients that allow for individually targeted tDCS treatment for motor rehabilitation after stroke, integrated with a direct monitoring of its physiological and behavioural effects.
In this project, we developed a technique to estimate the conductivity of cortical stroke using a combination of tDCS and EEG. In addition, we developed a data analysis pipeline to generate head models of chronic stroke patients based on a single T1-weighted MRI. Moreover, for large lesions, we found a high sensitivity of the electric field distribution to the lesion conductivity value and location. In the stimulation studies, unfortunately, we found that tDCS does not have an effect on cortical excitability or on motor learning. Combining the different techniques that we developed, we found that conventional motor tDCS in stroke patients can have the inverse effect in local brain areas when not accound from brain anatomy and stroke lesions. Alternatively, individualisation of tDCS configurations in chronic stroke patients increases stimulation strength and prevents negative stimulation of cortical targets.