title: Does trans-spinal direct current stimulation alter phrenic motoneurons and respiratory neuromechanical outputs in humans? A double-blind, sham-controlled, randomized, crossover study.
abstract: Although compelling evidence has demonstrated considerable neuroplasticity in the respiratory control system, few studies have explored the possibility of altering descending projections to phrenic motoneurons (PMNs) using noninvasive stimulation protocols. The present study was designed to investigate the immediate and long-lasting effects of a single session of transcutaneous spinal direct current stimulation (tsDCS), a promising technique for modulating spinal cord functions, on descending ventilatory commands in healthy humans. Using a double-blind, controlled, randomized, crossover approach, we examined the effects of anodal, cathodal, and sham tsDCS delivered to the C3-C5 level on (1) diaphragm motor-evoked potentials (DiMEPs) elicited by transcranial magnetic stimulation and (2) spontaneous ventilation, as measured by respiratory inductance plethysmography. Both anodal and cathodal tsDCS induced a progressive increase in DiMEP amplitude during stimulation that persisted for at least 15 min after current offset. Interestingly, cathodal, but not anodal, tsDCS induced a persistent increase in tidal volume. In addition, (1) short-interval intracortical inhibition, (2) nonlinear complexity of the tidal volume signal (related to medullary ventilatory command), (3) autonomic function, and (4) compound muscle action potentials evoked by cervical magnetic stimulation were unaffected by tsDCS. This suggests that tsDCS-induced aftereffects did not occur at brainstem or cortical levels and were likely not attributable to direct polarization of cranial nerves or ventral roots. Instead, we argue that tsDCS could induce sustained changes in PMN output. Increased tidal volume after cathodal tsDCS opens up the perspective of harnessing respiratory neuroplasticity as a therapeutic tool for the management of several respiratory disorders.
authors.affiliation: Sorbonne Universités, Université Pierre et Marie Curie (UPMC) Univ. Paris 06, UMR_S 1158, Neurophysiologie Respiratoire Expérimentale et Clinique, F-75005 Paris, France, Institut National de la Santé et de la Recherche Médicale (Inserm), UMR S 1158, Neurophysiologie Respiratoire Expérimentale et Clinique, F-75005 Paris, France.
authors.forename: Marie-Cécile
authors.initials: MC
authors.lastname: Niérat
authors.affiliation: Sorbonne Universités, Université Pierre et Marie Curie (UPMC) Univ. Paris 06, UMR_S 1158, Neurophysiologie Respiratoire Expérimentale et Clinique, F-75005 Paris, France, Institut National de la Santé et de la Recherche Médicale (Inserm), UMR S 1158, Neurophysiologie Respiratoire Expérimentale et Clinique, F-75005 Paris, France, Assistance Publique-Hôpitaux de Paris, Groupe Hospitalier Pitié-Salpêtrière Charles Foix, Service de Pneumologie et Réanimation Médicale (département R3S), F-75013 Paris, France, and.
authors.forename: Thomas
authors.initials: T
authors.lastname: Similowski
authors.affiliation: Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ. Paris 06, UMR S 1127, Institut du Cerveau et de la Moelle épinière, Centre de Neuro-imagerie de Recherche, F-75013 Paris, France jeancharles.lamy@gmail.com.
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Lamy
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D010791:Phrenic Nerve / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology*; D004561:Transcutaneous Electric Nerve Stimulation / Q000379:methods*; D055815:Young Adult
keywords: humans; phrenic motoneurons; plasticity; spinal DC stimulation