RT Journal Article
SR Electronic
T1 Cortical and Subcortical Effects of Transcutaneous Spinal Cord Stimulation in Humans with Tetraplegia
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 2633
OP 2643
DO 10.1523/JNEUROSCI.2374-19.2020
VO 40
IS 13
A1 Francisco D. Benavides
A1 Hang Jin Jo
A1 Henrik Lundell
A1 V. Reggie Edgerton
A1 Yuri Gerasimenko
A1 Monica A. Perez
YR 2020
UL http://www.jneurosci.org/content/40/13/2633.abstract
AB An increasing number of studies supports the view that transcutaneous electrical stimulation of the spinal cord (TESS) promotes functional recovery in humans with spinal cord injury (SCI). However, the neural mechanisms contributing to these effects remain poorly understood. Here we examined motor-evoked potentials in arm muscles elicited by cortical and subcortical stimulation of corticospinal axons before and after 20 min of TESS (30 Hz pulses with a 5 kHz carrier frequency) and sham-TESS applied between C5 and C6 spinous processes in males and females with and without chronic incomplete cervical SCI. The amplitude of subcortical, but not cortical, motor-evoked potentials increased in proximal and distal arm muscles for 75 min after TESS, but not sham-TESS, in control subjects and SCI participants, suggesting a subcortical origin for these effects. Intracortical inhibition, elicited by paired stimuli, increased after TESS in both groups. When TESS was applied without the 5 kHz carrier frequency both subcortical and cortical motor-evoked potentials were facilitated without changing intracortical inhibition, suggesting that the 5 kHz carrier frequency contributed to the cortical inhibitory effects. Hand and arm function improved largely when TESS was used with, compared with without, the 5 kHz carrier frequency. These novel observations demonstrate that TESS influences cortical and spinal networks, having an excitatory effect at the spinal level and an inhibitory effect at the cortical level. We hypothesized that these parallel effects contribute to further the recovery of limb function following SCI.SIGNIFICANCE STATEMENT Accumulating evidence supports the view that transcutaneous electrical stimulation of the spinal cord (TESS) promotes recovery of function in humans with spinal cord injury (SCI). Here, we show that a single session of TESS over the cervical spinal cord in individuals with incomplete chronic cervical SCI influenced in parallel the excitability cortical and spinal networks, having an excitatory effect at the spinal level and an inhibitory effect at the cortical level. Importantly, these parallel physiological effects had an impact on the magnitude of improvements in voluntary motor output.