Tommaso Bocci1, Matteo Caleo2, Beatrice Vannini3, Maurizio Vergari4, Filippo Cogiamanian4, Simone Rossi5, Alberto Priori4, Ferdinando Sartucci6. 1. 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. 2. CNR Neuroscience Institute, Pisa, Italy. 3. Department of Clinical and Experimental Medicine, Unit of Neurology, Pisa University Medical School, Via P. Savi, n. 40, I 56126, Pisa, Italy. 4. Department of Neurological Sciences, University of Milan, Fondazione IRCCS Ospedale Maggiore Policlinico, Milan, Italy. 5. Department of Neurological and Neurosensorial Sciences, Neurology and Clinical Neurophysiology Section, Brain Investigation and Neuromodulation Lab., Azienda Ospedaliera Universitaria Senese, Siena, Italy. 6. 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.
Abstract
BACKGROUND: Transcutaneous spinal Direct Current Stimulation (tsDCS) is a noninvasive technique based on the application of weak electrical currents over spinal cord. NEW METHOD: 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). DISCUSSION: 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.
BACKGROUND: Transcutaneous spinal Direct Current Stimulation (tsDCS) is a noninvasive technique based on the application of weak electrical currents over spinal cord. NEW METHOD: 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). DISCUSSION: 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.
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