Changes in H-Reflex Recruitment After Trans-Spinal Direct Current Stimulation With Multiple Electrode Configurations

Abstract

Trans-spinal direct current stimulation (tsDCS) is an electro-modulatory tool with possible application in the rehabilitation of spinal cord injury. TsDCS generates a small electric field, aiming to induce lasting, functional neuromodulation in the targeted neuronal networks. Earlier studies have shown significant modulatory effects after application of lumbar tsDCS. However, for clinical application, a better understanding of application specific factors is required. Our goal was to investigate the effect of different electrode configurations using lumbar spinal tsDCS on spinal excitability. We applied tsDCS (2.5 mA, 15 min) in 10 healthy subjects with three different electrode configurations: (1) Anode and cathode placed over vertebra T11, and the posterior left shoulder respectively (LSC-S) (one polarity), and (2) Both electrodes placed in equal distance (ED) (7 cm) above and below vertebra T11, investigated for two polarities (ED-Anodal/Cathodal). The soleus H-Reflex is measured before, during and after tsDCS in either electrode configuration or a sham condition. To account for genetic predispositions in response to direct current stimulation, subject BDNF genotype was assessed. Stimulation in configuration ED-Cathodal induced an amplitude reduction of the H-reflex, 30 min after tsDCS with respect to baseline, whereas none of the other configurations led to significant post intervention effects. BDNF genotype did not correlate with post intervention effects. Furthermore, we failed to replicate effects shown by a previous study, which highlights the need for a better understanding of methodological and subject specific influences on tsDCS outcome. The H-reflex depression after tsDCS (Config. ED-Cathodal) provides new insights and may foster our understanding of the working mechanism of tsDCS.

Modulation of torque evoked by wide-pulse, high-frequency neuromuscular electrical stimulation and the potential implications for rehabilitation and training

“…In the tsDCS trial there were also no changes in the H-reflex/M max ratio, consistent with previous studies in which anodal tsDCS applied for 15 min at the 11th thoracic vertebrae did not alter the soleus maximal H-reflex amplitude/M max ratio 20 , 52 . In contrast, Winkler, et al 20 reported that anodal tsDCS induced a lasting decrease in H-reflex post-activation depression, which may alter excitatory post-synaptic potentials.…”

The plasticity of nerve fibers: the prolonged effects of polarization of afferent fibers

“…142) and were only rarely compatible with an increase in the excitability of group Ia afferents. The positive results of Lamy et al (143) and some other studies might nevertheless be most relevant (36,144,145) and (37) in humans and (33) in mice. Lamy et al (143) demonstrated that anodal tsDCS (2.5 mA applied for 15 min at Th11) was followed by ".…”

Curated Model Development Using NEUROiD: A Web-Based NEUROmotor Integration and Design Platform

“…Frequency and intensity of stimulation is known to affect the recruitment patterns of neuronal cells (Courtine et al, 2016). Stimulus received by spinal cord elements are intricately related to cell sizes, orientations, and positions with respect to the electrodes, anatomy, cellular and synaptic electrophysiology and morphology of spinal cord (Kuck et al, 2017, 2018).…”