title: Frequency-dependent tuning of the human motor system induced by transcranial oscillatory potentials.
abstract: Different corticothalamic brain modules intrinsically oscillate at a "natural frequency" in a topographically organized manner. In "quiescent" human sensorimotor regions, the main detectable oscillatory activity peaks at ∼20 Hz, and partly contributes to determine the state of corticospinal excitability. Here, we showed that the transcranial application of an imperceptible, short-lasting (90 s) electric field oscillating at a physiological range increases corticospinal excitability online, with well defined frequency dependence and regional specificity. Indeed, the size of motor evoked potentials (MEPs) induced by navigated single-pulse TMS over the motor cortex significantly increased only during the local application of transcranial alternating current stimulation (tACS) at 20 Hz (β range). Other tACS frequencies (5, 10, and 40 Hz) applied on the motor cortex did not impact MEPs' size. Moreover, tACS applied on a control site (parietal cortex) and on a peripheral site (ulnar nerve) also failed to modulate MEPs. These results help clarifying the functional significance of the 20 Hz idling β rhythm of sensorimotor regions and suggest potential clinical applications of this approach.
authors.affiliation: Dipartimento di Neuroscienze, Sezione Neurologia e Neurofisiologia Clinica, Azienda Ospedaliera-Universitaria Senese, Policlinico Le Scotte, I-53100 Siena, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Feurra
authors.forename: Giovanni
authors.initials: G
authors.lastname: Bianco
authors.forename: Emiliano
authors.initials: E
authors.lastname: Santarnecchi
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Del Testa
authors.forename: Alessandro
authors.initials: A
authors.lastname: Rossi
authors.forename: Simone
authors.initials: S
authors.lastname: Rossi
mesh_terms: D000328:Adult; D004525:Efferent Pathways / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000166:cytology / Q000502:physiology*; D010296:Parietal Lobe / Q000166:cytology / Q000502:physiology; D011712:Pyramidal Tracts / Q000166:cytology / Q000502:physiology*; D013003:Somatosensory Cortex / Q000166:cytology / Q000502:physiology*; D013788:Thalamus / Q000166:cytology / Q000502:physiology; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D014459:Ulnar Nerve / Q000502:physiology; D055815:Young Adult