Transspinal direct current stimulation with an intensity of 2.5 mA does not affect the corticospinal system excitability and motor skills
BACKGROUND: Noninvasive brain stimulation effectively affects movements, including the spinal cord level. Stimulation effects are very sensitive to montage and protocols of applied stimulation because they can involve different neuronal mechanisms. AIM: This study aimed to estimate the effect of anodal transspinal direct current stimulation (tsDCS) with an intensity of 2.5 mA applied at the spinal cord level (C7–Th1 segments) with cervical enlargement on the corticospinal system excitability and motor skills. METHODS: The study involved 54 healthy adults aged 21.19±3.2 years. The effect of tsDCS was assessed using motorevoked potentials from the first dorsal interosseous (FDI) muscle by transcranial magnetic stimulation in the primary motor cortex before stimulation, immediately after stimulation, and after 15 min. RESULTS: The application of an 11-min anodal tsDCS with a current value of 2.5 mA at the C7–Th1 level did not affect the motorevoked potentials of FDI. Statistically, changes in motorevoked potentials amplitudes did not differ between groups receiving anodal tsDCS and sham stimulation. In addition, anodal tsDCS did not affect motor skills. An individual’s ability to coordinate fingers and manipulate objects effectively (a measure of dexterity) in the nine-hole peg test and pressing a key in response to a visual stimulus in the serial reaction time task did not differ from that with sham stimulation. CONCLUSION: 2.5 mA anodal tsDCS on cervical enlargement does not affect the corticospinal system excitability or change motor skills associated with precise hand movements.