The effect of tDCS on the excitability level of the human motor cortex in young and healthy subjects.

Abstract

Background: Transcranial Direct Current stimulation (tDCS) is a brain stimulation technique that is capable of inducing excitability changes in the human motor cortex. Therefore tDCS is proving to be a promising tool for neurological and neuropsychiatric rehabilitation. Objective: To investigate the effect of different tDCS intensities on the cortical excitability level in young and healthy subjects. Methods: Thirteen healthy right-handed male subjects participated in the study. In a randomized order, tDCS of 2.5mA, 1mA and sham stimulation were applied for ten minutes and administered at three different days. The Recruitment Curve (RC) was measured at baseline (pre), immediately after (post), 30 minutes (post30) and 60 minutes (post60) after intervention, using Transcranial Magnetic Stimulation (TMS). The Area under the Recruitment Curve (AURC) was calculated to compare for differences between tDCS conditions and for differences over time within tDCS conditions. Results: Excitability changes were significant between the 1mA and 2.5mA intervention at the post60 point in time when we corrected for baseline differences. No differences in AURC were found between other tDCS interventions. Over time analysis revealed significant excitability elevations after 2.5mA tDCS for pre-post30, pre-post60 and post-post30 comparison. Conclusion: The cortical excitability level can be influenced by 2.5mA tDCS. More specifically we found differences between 2.5mA and 1mA stimulation at 60 minutes post intervention and over time after 2