title: An unexpected target of spinal direct current stimulation: Interhemispheric connectivity in humans.
abstract: BACKGROUND
  Transcutaneous spinal Direct Current Stimulation (tsDCS) is a noninvasive technique based on the application of weak electrical currents over spinal cord.
  
  
  METHODS
  We studied the effects of tsDCS on interhemispheric motor connectivity and visual processing by evaluating changes in ipsilateral Silent Period (iSP), Transcallosal Conduction Time (TCT) and hemifield Visual Evoked Potentials (hVEPs), before (T0) and at a different intervals following sham, anodal and cathodal tsDCS (T9-T11 level, 2.0 mA, 20'). Motor Evoked Potentials (MEPs) were recorded from abductor pollicis brevis (APB), abductor hallucis (AH) and deltoid muscles. hVEPs were recorded bilaterally by reversal of a horizontal square wave grating with the display positioned in the right hemifield.
  
  
  RESULTS
  Anodal tsDCS increased TCT (p < 0.001) and the interhemispheric delay for both the main VEP components (N1: p = 0.0003; P1: p < 0.0001), dampening at the same time iSP duration (APB: p < 0.0001; AH: p = 0.0005; deltoid: p < 0.0001), while cathodal stimulation elicited opposite effects (p < 0.0001).
  
  
  CONCLUSIONS
  tsDCS modulates interhemispheric processing in a polarity-specific manner, with anodal stimulation leading to a functional disconnection between hemispheres. tsDCS would be a new promising therapeutic tool in managing a number of human diseases characterized by an impaired interhemispheric balance, or an early rehabilitation strategy in patients with acute brain lesions, when other non-invasive brain stimulation techniques (NIBS) are not indicated due to safety concerns.
authors.affiliation: Department of Clinical and Experimental Medicine, Unit of Neurology, Pisa University Medical School, Via P. Savi, n. 40, I 56126, Pisa, Italy; Department of Neurological and Neurosensorial Sciences, Neurology and Clinical Neurophysiology Section, Brain Investigation and Neuromodulation Lab., Azienda Ospedaliera Universitaria Senese, Siena, Italy.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Bocci
authors.affiliation: CNR Neuroscience Institute, Pisa, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Caleo
authors.affiliation: Department of Clinical and Experimental Medicine, Unit of Neurology, Pisa University Medical School, Via P. Savi, n. 40, I 56126, Pisa, Italy.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Vannini
authors.affiliation: Department of Neurological Sciences, University of Milan, Fondazione IRCCS Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Vergari
authors.affiliation: Department of Neurological Sciences, University of Milan, Fondazione IRCCS Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Cogiamanian
authors.affiliation: Department of Neurological and Neurosensorial Sciences, Neurology and Clinical Neurophysiology Section, Brain Investigation and Neuromodulation Lab., Azienda Ospedaliera Universitaria Senese, Siena, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Rossi
authors.affiliation: Department of Neurological Sciences, University of Milan, Fondazione IRCCS Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Priori
authors.affiliation: Department of Clinical and Experimental Medicine, Unit of Neurology, Pisa University Medical School, Via P. Savi, n. 40, I 56126, Pisa, Italy; CNR Neuroscience Institute, Pisa, Italy; Department of Clinical and Experimental Medicine, Cisanello Neurology Unit, Azienda Ospedaliera Universitaria Pisana, Pisa, Italy. Electronic address: ferdinando.sartucci@med.unipi.it.
authors.forename: Ferdinando
authors.initials: F
authors.lastname: Sartucci
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D004311:Double-Blind Method; D004599:Electric Stimulation Therapy / Q000379:methods*; D019054:Evoked Potentials, Motor / Q000502:physiology; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D011897:Random Allocation; D013116:Spinal Cord / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
keywords: Corpus callosum; Hemifield visual evoked potentials; Interhemispheric processing; Ipsilateral silent period; Supraspinal effects; Transcutaneous spinal direct current stimulation; Visual system; tsDCS