Investigation The Effect of Conventional Vs. Individualized tDCS Intensity to Achieve Uniform E-Fields

Inclusion Criteria: Right-handed volunteers, assessed by Edinburgh handedness inventory Normal or corrected-to-normal vision Greater than or equal to 18 years old Relapsing-remitting type of MS (RRMS) Moderate disability EDSS score ≤ 6.5 Free of relapsing attack at least a month before recruitment Exclusion Criteria: Subject recently had a seizure or epilepsy Subject is a habitual smoker; Subject has a history of any major disease that may interfere with the investigations (especially liver and kidney disease, upper limb pathologies, history of significant multiple traumas, or diabetes) or cancer; Subject has any history of a major neurological disorder in addition to MS (including previous severe brain trauma and cognitive impairment) or known cerebral structural abnormalities; Subject has a diagnosed mental disorder (e.g., depression, bipolar disorder, schizophrenia, psychoses); Subject is currently a user (including ''recreational use'') of any illicit drugs or has a history of drug or alcohol abuse; Subject has significant abnormalities on T1/T2 MRI scan; Subject has a contra-indication for MRI scanning or TMS measurements (see screening forms for MRI and TMS); Subject does not understand the study procedure; Subject is unwilling or unable to perform all study procedures, or is considered unsuitable in any way by the principal investigator; Subject is not able to perform the motor tasks; Subject is (potentially) pregnant (in case of doubt, hCG test will be conducted in female participants); subject is breastfeeding at the time of the study; Subject chronically uses medication, especially sedatives or sleep medication (contraceptives allowed). Other medication that is only taken as needed will be allowed at the investigator's discretion; Using TMS, no (sufficiently stable) MEPs can be evoked at left M1;