Effect of tsDCS applied with different electrode configurations on the lumbar spinal circuits

Spinal Cord Injury (SCI) is a severe injury to the central nervous system (CNS) which, despite a heavy post injury rehabilitation regime, often leaves patients bound to a wheelchair or with other impairments diminishing their quality of life. Trans-spinal direct current stimulation (tsDCS) is a promising new technique for the treatment of SCI. During tsDCS a small direct current is applied to the spinal cord via two or more stimulation electrodes, placed over the backbone of a subject. The technique aims to alter the response of the neural pathways in the spinal cord, which is hypothesized to have a positive effect on the recovery of the damaged spinal cord neuronal networks. The objective of this study, is to assess how tsDCS modulates the excitability of the spinal cord and whether this modulation is dependent on the electrode placement configurations. The primary goal is to compare a new electrode placement configuration with one that is commonly used in previous tsDCS studies. This is assessed using the H- Reflex, whereby the novel configuration is hypothesized to have a larger modulatory effect on the spinal circuits. The two different configurations are: 1) cathode and anode placed on the T11 vertebra and the left shoulder blade respectively (commonly used) and 2) the two electrodes placed over the spinal cord, 7 centimeters apart and centered around the 11 thoracic vertebra. TsDCS is applied on the lumbar spinal cord for a period of 15 minutes with a current of 2,5mA. The ascending part of the H-reflex recruitment curve is measured before, during and after tsDCS. We hereby present the outcome of the aforementioned study as well as the current progress of our laboratory with respect to the effect of tsDCS on the spinal circuits. We hope that our work will be able to contribute to the effectivity of tsDCS, which could possibly be applied in the rehabilitation of spinal cord injured subjects in the future.