Effects of paired transcutaneous electrical stimulation delivered at single and dual sites over lumbosacral spinal cord

Abstract

It was demonstrated previously that transcutaneous electrical stimulation of multiple sites over the spinal cord is more effective in inducing robust locomotor behavior as compared to the stimulation of single sites alone in both animal and human models. To explore the effects and mechanisms of interactions during multi-site spinal cord stimulation we delivered transcutaneous electrical stimulation to the single or dual locations over the spinal cord corresponding to approximately L2 and S1 segments. Spinally evoked motor potentials in the leg muscles were investigated using single and paired pulses of 1 ms duration with conditioning-test intervals (CTIs) of 5 and 50 ms. We observed considerable post-stimulation modulatory effects which depended on CTIs, as well as on whether the paired stimuli were delivered at a single or dual locations, the rostro-caudal relation between the conditioning and test stimuli, and on the muscle studied. At CTI-5, the paired stimulation delivered at single locations (L2 or S1) provided strong inhibitory effects, evidenced by the attenuation of the compound responses as compared with responses from either single site. In contrast, during L2-S1 paradigm, the compound responses were potentiated. At CTI-50, the magnitude of inhibition did not differ among paired stimulation paradigms. Our results suggest that electrical stimuli delivered to dual sites over the lumbosacral enlargement in rostral-to-caudal order, may recruit different populations of motor neurons initially through projecting sensory and intraspinal connections and then directly, resulting in potentiation of the compound spinally evoked motor potentials. The interactive and synergistic effects indicate multi-segmental convergence of descending and ascending influences on the neuronal circuitries during electrical spinal cord stimulation.

Current Principles of Motor Control, with Special Reference to Vertebrate Locomotion

“…Intrathecal electric stimulation of afferents and particularly the dorsal columns or peripheral stimulation have been shown to promote locomotor activity or facilitate other movements (19,88,89,241,243,330,404,405,462). Currently, this approach seems to be the most promising way to elevate the excitability in the spinal cord networks of spinal cord injury patients to a degree so that the remaining brain stem fibers from LGPi can initiate the locomotor activity, particularly if combined with locomotor training.…”

Multilevel Analysis of Locomotion in Immature Preparations Suggests Innovative Strategies to Reactivate Stepping after Spinal Cord Injury

“…In these preparations, electrical stimulation with stereotyped trains of square impulses triggered brief episodes of electrical oscillations, alternating between flexor and extensor motor pools on both sides of the cord (fictive locomotion rhythm, FL; [25]), when selectively delivered through tight fitting electrodes to either DRs [147] or sacrocaudal afferents [148]. In addition, activation of multiple DRs with staggered pulses [149,150] effectively generated FL, indicating a multi-segmental convergence of afferent inputs on neuronal circuits during electrical spinal cord stimulation, as also reported in both in vivo animals [151] and in humans [100,152].…”

Combination of Functional Electrical Stimulation and Noninvasive Spinal Cord Electrical Stimulation for Movement Rehabilitation of the Children with Cerebral Palsy

“…Previous studies have shown that improved locomotor performance is closely associated with improved coordination of motor pools [5]. TSCS at T11 and L1 vertebral levels of proximal and distal motor pools in paralyzed subjects are facilitated [24]. This effect is evident in spinal motor evoked potentials of proximal and distal leg muscles to single stimulation pulses [23].…”