Transspinal direct current stimulation with an intensity of 2.5 mA does not affect the corticospinal system excitability and motor skills

Abstract

BACKGROUND: Non-invasive brain stimulation is an effective way to affect movement production, including the spinal cord level. It is known, that the stimulation effects are very sensitive to montage and protocols of applied stimulation, because it can involve different neuronal mechanisms. 
 AIM: The purpose of the study was to estimate the effect of anodal transspinal direct current stimulation (tsDCS) with intensity 2,5 mA applied at the level of the cervical enlargement of the spinal cord (C7-Th1 segments) on the corticospinal system (CSS) excitability and motor skills. 
 METHODS: The study involved 54 healthy adults aged 21,19 3,2 years. The effect of tsDCS was assessed using motor evoked potentials (MEP) from the first dorsal interosseous (FDI) muscle by transcranial magnetic stimulation in the primary motor cortex before stimulation, immediately after stimulation, and after 15 minutes.
 RESULTS: Our results showed that the application of an 11-minute anodal tsDCS at the level of the cervical spine C7-Th1 with a current value of 2.5 mA does not affect the MEP of FDI. The statistical analysis demonstrated that the dynamics of MEP amplitudes did not differ between groups receiving anodal tsDCS and sham stimulation. Also, anodal tsDCS did not affect motor skills. An individual's ability to coordinate fingers and manipulate objects effectively (a measure of dexterity) in 9-HPT, and pressing a key in response to a visual stimulus in SRT, did not differ from sham stimulation. 
 CONCLUSION: Therefore, it can be assumed that 2.5 mA anodal tsDCS on the cervical enlargement of the spinal cord does not affect the CSS excitability or change motor skills associated with precise hand movements.