Abstract
Non-invasive, weak direct current stimulation can induce changes in excitability of underlying neural tissue. Many studies have used transcranial direct current stimulation to induce changes in the brain, however more recently a number of studies have used transcutaneous spinal direct current stimulation to induce changes in the spinal cord. This study further characterises the effects following cervical transcutaneous spinal direct current stimulation on motor pathways supplying the upper limb. In Study 1, on two separate days, participants (n = 12, 5 F) received 20 minutes of either real or sham direct current stimulation at 3 mA through electrodes placed in an anterior-posterior configuration over the neck (anode anterior). Biceps brachii, flexor carpi radialis and first dorsal interosseous responses to transcranial magnetic stimulation (motor evoked potentials) and cervicomedullary stimulation (cervicomedullary motor evoked potentials) were measured before and after real or sham stimulation. In Study 2, on two separate days, participants (n = 12, 7 F) received either real or sham direct current stimulation in the same way as for Study 1. Before and after real or sham stimulation, median nerve stimulation elicited M waves and H reflexes in the flexor carpi radialis. H-reflex recruitment curves and homosynaptic depression of the H reflex were assessed. Results show that the effects of real and sham direct current stimulation did not differ for motor evoked potentials or cervicomedullary motor evoked potentials for any muscle, nor for H-reflex recruitment curve parameters or homosynaptic depression. Cervical transcutaneous spinal direct current stimulation with the parameters described here does not modify motor responses to corticospinal stimulation nor does it modify H reflexes of the upper limb. These results are important for the emerging field of transcutaneous spinal direct current stimulation.
Highlights
Transcranial direct current stimulation is a well-documented technique involving the application of weak, non-invasive currents to the scalp to induce changes in the excitability of underlying neural tissue
There were no significant differences in baseline cervicomedullary MEPs (CMEPs) or motor evoked potentials (MEPs) elicited prior to the delivery of real or sham transcutaneous spinal direct current stimulation (tsDCS) for any muscle (Table 1; p > 0.05)
Cervical tsDCS had no effect on CMEPs in any muscle
Summary
Transcranial direct current stimulation (tDCS) is a well-documented technique involving the application of weak, non-invasive currents to the scalp to induce changes in the excitability of underlying neural tissue (for review see: [1]). Cervical transcutaneous spinal direct current stimulation collection and analysis, decision to publish, or preparation of the manuscript
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