title: Low-frequency rTMS inhibitory effects in the primary motor cortex: Insights from TMS-evoked potentials.
abstract: The neuromodulatory effects of repetitive transcranial magnetic stimulation (rTMS) have been mostly investigated by peripheral motor-evoked potentials (MEPs). New TMS-compatible EEG systems allow a direct investigation of the stimulation effects through the analysis of TMS-evoked potentials (TEPs). We investigated the effects of 1-Hz rTMS over the primary motor cortex (M1) of 15 healthy volunteers on TEP evoked by single pulse TMS over the same area. A second experiment in which rTMS was delivered over the primary visual cortex (V1) of 15 healthy volunteers was conducted to examine the spatial specificity of the effects. Single-pulse TMS evoked four main components: P30, N45, P60 and N100. M1-rTMS resulted in a significant decrease of MEP amplitude and in a significant increase of P60 and N100 amplitude. There was no effect after V1-rTMS. 1-Hz rTMS appears to increase the amount of inhibition following a TMS pulse, as demonstrated by the higher N100 and P60, which are thought to originate from GABAb-mediated inhibitory post-synaptic potentials. Our results confirm the reliability of the TMS-evoked N100 as a marker of cortical inhibition and provide insight into the neuromodulatory effects of 1-Hz rTMS. The present finding could be of relevance for therapeutic and diagnostic purposes.
authors.affiliation: Lifespan Cognitive Neuroscience Lab, Department of General Psychology, University of Padua, Via Venezia 8, Padua 35131, Italy; Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, Queen Square 33, London WC1N 3BG, UK. Electronic address: eliasc@live.it.
authors.forename: Elias P
authors.initials: EP
authors.lastname: Casula
authors.affiliation: Lifespan Cognitive Neuroscience Lab, Department of General Psychology, University of Padua, Via Venezia 8, Padua 35131, Italy.
authors.forename: Vincenza
authors.initials: V
authors.lastname: Tarantino
authors.affiliation: Faculty of Education, Free University of Bozen-Bolzano, Viale Ratisbona 16, 39042 Bressanone-Brixen, Italy; Centro di Neuroscienze Cognitive Applicate, Via Caio Manilio 30, Rome 00174, Italy.
authors.forename: Demis
authors.initials: D
authors.lastname: Basso
authors.affiliation: Lifespan Cognitive Neuroscience Lab, Department of General Psychology, University of Padua, Via Venezia 8, Padua 35131, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Arcara
authors.affiliation: Lifespan Cognitive Neuroscience Lab, Department of General Psychology, University of Padua, Via Venezia 8, Padua 35131, Italy.
authors.forename: Giuliana
authors.initials: G
authors.lastname: Marino
authors.affiliation: Department of Information Engineering, University of Padua, Via Gradenigo 6/B, Padua 35131, Italy.
authors.forename: Gianna Maria
authors.initials: GM
authors.lastname: Toffolo
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, Queen Square 33, London WC1N 3BG, UK.
authors.forename: John C
authors.initials: JC
authors.lastname: Rothwell
authors.affiliation: Lifespan Cognitive Neuroscience Lab, Department of General Psychology, University of Padua, Via Venezia 8, Padua 35131, Italy.
authors.forename: Patrizia S
authors.initials: PS
authors.lastname: Bisiacchi
mesh_terms: D000328:Adult; D004569:Electroencephalography; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009433:Neural Inhibition; D050781:Transcranial Magnetic Stimulation; D014793:Visual Cortex / Q000502:physiology*; D055815:Young Adult
keywords: EEG; GABAb; Inhibition; N100; TEPs; TMS