Reliability of tDCS Induced Corticomotor Excitability in Lower Limb Motor Cortex of Healthy Individuals

Noninvasive brain stimulation techniques, such as transcranial direct current stimulation (tDCS), have emerged as a promising tool to enhance motor function by modulating corticomotor excitability. Anodal tDCS has shown to modulate corticomotor excitability and improve motor function in those with neurological disease. However, there is limited information on the reliability of these effects. In order to increase the potential of tDCS as a clinical tool, it is important to be able to demonstrate that the effects of tDCS are reliable, and individuals respond to the intervention in a predictable manner when retested. The main purpose of this thesis was to explore the test-retest effects of transcranial direct current stimulation (tDCS) applied in conjunction with a skilled motor learning task versus when applied at rest. Fifteen healthy participants were recruited and tested under two stimulation conditions: 1) anodal tDCS during a motor task (tDCS-task) and 2) anodal tDCS at rest (tDCS-rest). The outcome measures evaluated were changes in the corticomotor excitability using single pulse transcranial magnetic stimulation. Results revealed that tDCS application during practice of a skilled motor task resulted in reduced variability in TMS measures compared to tDCS applied in the absence of motor practice. Testing at higher stimulus intensities (140% AMT) and examining input output response curves provided a more reliable method of testing the effects of tDCS.