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.
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