Affiliations: [a] Department of Physical Medicine and Rehabilitation, University of Kentucky, Lexington, KY, USA
| [b] Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center, Houston, TX, USA
| [c] Department of Biostatistics, College of Public Health, University of Kentucky, Lexington, KY, USA
| [d]
Encompass Health Cardinal Hill Rehabilitation Hospital, Lexington, KY, USA
Correspondence:
[*]
Address for correspondence: Lumy Sawaki, Department of Physical Medicine and Rehabilitation, University of Kentucky, 2050 Versailles Road, Lexington, KY 40504, USA. Tel.: +1 859 323 6226; E-mail: lumy.sawaki@uky.edu.
Note: [1] These co-first authors contributed equally to this work.
Abstract: BACKGROUND:Non-invasive transcranial direct current stimulation has been shown to modulate cortical excitability in various studies. Similarly, recent preliminary studies suggest that transcutaneous spinal direct current stimulation (tsDCS) may engender a modulation effect on spinal and cortical neurons. OBJECTIVE:The purpose of this study was to evaluate the dose-response effects of tsDCS in healthy subjects and thereby lay groundwork for expanding treatment options for patients with spinal cord injury (SCI). METHODS:Nine healthy subjects received each of the following 2 tsDCS conditions: Anodal and cathodal, in random order with at least 1 week washout period between each session. In order to test safety and dose response, various current intensities were used (2, 2.5 and 3 mA) for 20 minutes. The active electrode was placed vertically over T10–T11, and the reference electrode was placed over the left shoulder. To evaluate corticospinal excitability, motor evoked potentials over soleus muscle elicited by transcranial magnetic stimulation were measured. To assess spinal cord excitability, H- and M- wave over soleus muscle to calculate Hmax/ Mmax ratio were measured. RESULTS:Linear regression showed a dose response with cathodal tsDCS on motor evoked potentials measured from the left leg as well as with anodal tsDCS on Hmax/ Mmax ratio measured from the left leg. CONCLUSIONS:These findings indicate tsDCS effects are dose-dependent. These effects should be investigated in a larger sample.
Keywords: Neuromodulation, transvertebral spinal direct current stimulation, spinal cord, neurorehabilitation
