Improving cognitive performance in MS by transcranial alternating current brain stimulation (tACS); a pilot study

INTERVENTION: Transcranial alternating current stimulation (tACS) in theta range (6 Hz) applied over frontal and parietal regions synchronously CONDITION: Multiple sclerosis (MS) ; ; PRIMARY OUTCOME: 1. Trial endpoints in coherence of EEG signal in theta range; ; 2. Difference in reaction times on Vienna Reaction Time task.; ; SECONDARY OUTCOME: 1. baseline measures of cognitive performance and lesion load estimated from DTI and MTR measurements as predictors/covariates. ; ; 2.post ‐ vs pre –stimulation Neuropsychological evaluation (NPE) scores INCLUSION CRITERIA: ‐ MS patients with subjective complaints of cognitive impairment or on the recommendation of attending neurologist; ‐ age 30‐60 years; ‐ MRI compatible; ‐ decreased values (1.5 standard deviations below the normative control values or below cut‐off value for deviation) on at least 2 tests from NPE battery. ‐ Diagnosis of MS according to the 2010 McDonald criteria; ‐ No relapse in the last 3 months before the test; ‐ Signed written informed consent; ‐ Right handedness.