Centre Hospitalier Le Vinatier 1 article published in JoVE Neuroscience Combining a Breath-Synchronized Olfactometer with Brain Simulation to Study the Impact of Odors on Corticospinal Excitability and Effective Connectivity Cécilia Neige1,2, Laetitia Imbert1,2, Maylis Dumas1,2, Anna Athanassi3, Marc Thévenet3, Nathalie Mandairon3, Jérôme Brunelin1,2 1PSYR2, Centre de Recherche en Neurosciences de Lyon, Institut National de la Santé et de la Recherche Médicale U1028, Centre National de la Recherche Scientifique UMR5292, Université Claude Bernard Lyon 1, 2Centre Hospitalier Le Vinatier, 3NEUROPOP, Centre de Recherche en Neurosciences de Lyon, Institut National de la Santé et de la Recherche Médicale U1028, Centre National de la Recherche Scientifique UMR5292, Université Claude Bernard Lyon 1 This paper describes using a breath-synchronized olfactometer to trigger single- and dual-coil transcranial magnetic stimulation (TMS) during odorant presentation synchronized to human nasal breathing. This combination allows us to objectively investigate how pleasant and unpleasant odors impact corticospinal excitability and brain-effective connectivity in a given individual.