title: Cathodal transcutaneous spinal direct current stimulation (tsDCS) improves motor unit recruitment in healthy subjects.
abstract: Transcutaneous spinal direct current stimulation (tsDCS) is a new promising technique for modulating spinal cord function in humans. However, its effects on corticospinal pathways and lower motorneuron excitability are poorly understood. We studied the effects of tsDCS on motor unit recruitment by evaluating changes in motor unit number (MUNE) and peripheral silent period (PSP) after sham (s-tsDCS), anodal (a-tsDCS) and cathodal (c-tsDCS) tsDCS applied either over the cervical or the lower thoracic spinal cord in healthy subjects. For the calculation of MUNE we used the multipoint incremental technique recording from either the ulnar nerve innervated abductor digiti minimi (ADM) or the median nerve innervated abductor pollicis brevis (APB) muscle. c-tsDCS dramatically increases MUNE values following cervical polarization, while sham and anodal polarization have no significant effect (APB: F(4,99)=26.4, p<0.001, two-way repeated measures ANOVA with "time" and "stimulation" as factors; ADM: F(4,99)=22.1, p<0.0001). At the same time, c-tsDCS dampened PSP respect to sham and anodal conditions (p<0.0001). Interestingly, also thoracic c-tsDCS significantly improved motor unit recruitment compared with both s-tsDCS and a-tsDCS (APB: F(4,99)=20.1, p<0.0001; ADM: F(4,99)=16.6, p<0.0001). Our data in healthy subjects suggest that tsDCS, possibly also through supraspinal effects, could provide a novel therapeutic tool in managing several pathological conditions characterized by reduced motor unit recruitment, such as stroke and spinal cord injuries.
authors: Department of Clinical and Experimental Medicine, Unit of Neurology, Pisa University Medical School, Pisa, Italy; Department of Neurological and Neurosensorial Sciences, Neurology and Clinical Neurophysiology Section, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
authors: Tommaso
authors: T
authors: Bocci
authors: Department of Clinical and Experimental Medicine, Unit of Neurology, Pisa University Medical School, Pisa, Italy.
authors: Beatrice
authors: B
authors: Vannini
authors: Department of Neurological and Neurosensorial Sciences, Neurology and Clinical Neurophysiology Section, Azienda Ospedaliera Universitaria Senese, Siena, Italy; Department of Clinical and Experimental Medicine, Cisanello Neurology Unit, Pisa University Medical School, Pisa, Italy.
authors: Antonio
authors: A
authors: Torzini
authors: Department of Clinical and Experimental Medicine, Cisanello Neurology Unit, Pisa University Medical School, Pisa, Italy; CNR Neuroscience Institute, Pisa, Italy.
authors: Andrea
authors: A
authors: Mazzatenta
authors: Department of Neurological Sciences, University of Milan, Fondazione IRCCS Ospedale Maggiore Policlinico, Milan, Italy.
authors: Maurizio
authors: M
authors: Vergari
authors: Department of Neurological Sciences, University of Milan, Fondazione IRCCS Ospedale Maggiore Policlinico, Milan, Italy.
authors: Filippo
authors: F
authors: Cogiamanian
authors: Department of Neurological Sciences, University of Milan, Fondazione IRCCS Ospedale Maggiore Policlinico, Milan, Italy.
authors: Alberto
authors: A
authors: Priori
authors: Department of Clinical and Experimental Medicine, Unit of Neurology, Pisa University Medical School, Pisa, Italy; Department of Clinical and Experimental Medicine, Cisanello Neurology Unit, Pisa University Medical School, Pisa, Italy; CNR Neuroscience Institute, Pisa, Italy. Electronic address: f.sartucci@neuro.med.unipi.it.
authors: Ferdinando
authors: F
authors: Sartucci
mesh_terms: D000328:Adult; D002574:Cervical Vertebrae; D004566:Electrodes; D005260:Female; D006801:Humans; D008297:Male; D011999:Recruitment, Neurophysiological; D013116:Spinal Cord / Q000502:physiology*; D013904:Thoracic Vertebrae; D004561:Transcutaneous Electric Nerve Stimulation; D055815:Young Adult
keywords: Motor system; Motor unit number estimation; Motor unit recruitment; Motorneuron excitability; Transcutaneous spinal direct current stimulation; tsDCS