Universidad de Investigacion para la Generacion y Sintesis de Evidencia en Salud, Universidad San Ignacio de Loyola 1 article published in JoVE Neuroscience Measuring Contralateral Silent Period Induced by Single-Pulse Transcranial Magnetic Stimulation to Investigate M1 Corticospinal Inhibition Ingrid Rebello-Sanchez1, Joao Parente1, Kevin Pacheco-Barrios1,2, Anna Marduy1, Danielle Carolina Pimenta1, Daniel Lima1, Eric Slawka1, Alejandra Cardenas-Rojas1, Gleysson Rodrigues Rosa1, Kamran Nazim3, Abhishek Datta3,4, Felipe Fregni1 1Neuromodulation Center and Center for Clinical Research Learning, Spaulding Rehabilitation Hospital and Massachusetts General Hospital, Harvard Medical School, 2Universidad de Investigación para la Generación y Síntesis de Evidencia en Salud, Universidad San Ignacio de Loyola, 3Research and Development, Soterix Medical, 4City College of New York Contralateral silent period (cSP) assessment is a promising biomarker to index cortical excitability and treatment response. We demonstrate a protocol to assess cSP intended for studying M1 corticospinal inhibition of upper and lower limbs.