title: 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.
authors.affiliation: Spaulding Neuromodulation Center, Department of Physical Medicine &Rehabilitation, Spaulding Rehabilitation Hospital and Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.|Engineering Science, Loyola University Chicago, IL, USA.
authors.forename: Chiun-Fan
authors.initials: CF
authors.lastname: Chen
authors.affiliation: Department of Biomedical Engineering, The City College of the City University of New York, NY, USA.
authors.forename: Marom
authors.initials: M
authors.lastname: Bikson
authors.affiliation: Department of Physical Therapy and Assistive Technologies, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Li-Wei
authors.initials: LW
authors.lastname: Chou
authors.affiliation: Spaulding Neuromodulation Center, Department of Physical Medicine &Rehabilitation, Spaulding Rehabilitation Hospital and Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.|School of Rehabilitation Science, Shanghai University of Traditional Chinese Medicine, Shanghai, China.
authors.forename: Chunlei
authors.initials: C
authors.lastname: Shan
authors.affiliation: Department of Biomedical Engineering, The City College of the City University of New York, NY, USA.
authors.forename: Niranjan
authors.initials: N
authors.lastname: Khadka
authors.affiliation: Department of Physical Medicine and Rehabilitation, National Taiwan University College of Medicine and National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Wen-Shiang
authors.initials: WS
authors.lastname: Chen
authors.affiliation: Spaulding Neuromodulation Center, Department of Physical Medicine &Rehabilitation, Spaulding Rehabilitation Hospital and Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Felipe
authors.initials: F
authors.lastname: Fregni
mesh_terms: D000818:Animals; D003198:Computer Simulation; D004558:Electric Stimulation; D055724:Electrophysiological Phenomena; D008297:Male; D008959:Models, Neurological; D015233:Models, Statistical; D010525:Peripheral Nerves / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology*; D011817:Rabbits