Higher-order power harmonics of pulsed electrical stimulation modulates corticospinal contribution of peripheral nerve stimulation

Abstract

It is well established that electrical-stimulation frequency is crucial to determining the scale of induced neuromodulation, particularly when attempting to modulate corticospinal excitability. However, the modulatory effects of stimulation frequency are not only determined by its absolute value but also by other parameters such as power at harmonics. The stimulus pulse shape further influences parameters such as excitation threshold and fiber selectivity. The explicit role of the power in these harmonics in determining the outcome of stimulation has not previously been analyzed. In this study, we adopted an animal model of peripheral electrical stimulation that includes an amplitude-adapted pulse train which induces force enhancements with a corticospinal contribution. We report that the electrical-stimulation-induced force enhancements were correlated with the amplitude of stimulation power harmonics during the amplitude-adapted pulse train. In an exploratory analysis, different levels of correlation were observed between force enhancement and power harmonics of 20–80 Hz (r = 0.4247, p = 0.0243), 100–180 Hz (r = 0.5894, p = 0.0001), 200–280 Hz (r = 0.7002, p < 0.0001), 300–380 Hz (r = 0.7449, p < 0.0001), 400–480 Hz (r = 0.7906, p < 0.0001), 500–600 Hz (r = 0.7717, p < 0.0001), indicating a trend of increasing correlation, specifically at higher order frequency power harmonics. This is a pilot, but important first demonstration that power at high order harmonics in the frequency spectrum of electrical stimulation pulses may contribute to neuromodulation, thus warrant explicit attention in therapy design and analysis.

Electrical impulse effects on degenerative human annulus fibrosus model to reduce disc pain using micro-electrical impulse-on-a-chip

“…Additionally, ES influences the polarization state of the cell membrane, causing changes in the cellular microenvironment 25 . The human body generates bioelectricity through ion channels, which perform various biological processes, in the range of 100–300 Hz 26–28 . ES has been applied to spinal cord injuries in an attempt to develop clinical therapies 29 .…”

Transcranial direct current stimulation enhances recovery from motor deficits following hypoxia-ischemia in neonatal rats

“…There is much debate about the underlying mechanisms behind the effects of tDCS [20]. There has been growing knowledge of how peripheral nerve stimulation can affect the CNS reportedly producing many similar effects to that of tDCS [21]. The data suggesting a high percentage of current shunting through the highly conductive scalp may suggest that the main mechanism of tDCS depends on the nerves under the skin [22].…”

The effect of combined transcranial pulsed current stimulation and transcutaneous electrical nerve stimulation on lower limb spasticity in children with spastic cerebral palsy classified on Gross Motor Function Classification System (GMFCS) levels III–V: a randomized and controlled clinical study

“…On the spine, we applied two pairs of electrodes on the cervicothoracic and thoracolumbar regions following evidence in transpinal studies [34,35] that stimulating these regions could affect ipsilateral and contralateral actions of corticospinal neurons to enhance corticospinal excitability; On the lower limbs, three pairs of 400 Hz TENS electrodes were applied directly on agonist spastic muscles (adductor longus, rectus femoris, and gastrocnemius), supported by evidence that high frequency (³ 99 Hz) TENS on the periphery could recruit larger diameter afferent during stimulation to relieve spasticity that was accompanied by a decrease on H-reflex amplitude, which was not observed when lower frequencies (<50 Hz) were used [71][72][73]. In fact, 400 Hz stimulation frequency was applied for all six pairs of electrodes to maximize force enhancement during stimulation to increase effects on corticospinal neuromodulation, following evidence [74] that observed the induced force enhancement during tPCS stimulation was most highly correlated with higher order power harmonics of the stimulation waveform at 400-480 Hz.…”