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This Article Full Text Full Text (PDF) All Versions of this Article: 575/2/657    most recent jphysiol.2006.114025v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Quartarone, A. Articles by Roman Siebner, H. Search for Related Content PubMed PubMed Citation Articles by Quartarone, A. Articles by Roman Siebner, H. Related Collections Integrative

¹ Department of Neuroscience, Psychiatric and Anaethesiological Sciences, University of Messina, Italy
² Fondazione Istituto San Raffaele Giuseppe Giglio, Cefalù (PA), Italy
³ Department of Neurology, Christian-Albrechts-University, Kiel, Germany
⁴ NeuroImageNord, Hamburg-Kiel-Lübeck, Germany

Repetitive transcranial magnetic stimulation (rTMS) or repetitive electrical peripheral nerve stimulation (rENS) can induce changes in the excitability of the human motor cortex (M1) that is often short-lasting and variable, and occurs only after prolonged periods of stimulation. In 10 healthy volunteers, we used a new repetitive paired associative stimulation (rPAS) protocol to facilitate and prolong the effects of rENS and rTMS on cortical excitability. Sub-motor threshold 5 Hz rENS of the right median nerve was synchronized with submotor threshold 5 Hz rTMS of the left M1 at a constant interval for 2 min. The interstimulus interval (ISI) between the peripheral stimulus and the transcranial stimulation was set at 10 ms (5 Hz rPAS_10ms) or 25 ms (5 Hz rPAS_25ms). TMS was given over the hot spot of the right abductor pollicis brevis (APB) muscle. Before and after rPAS, we measured the amplitude of the unconditioned motor evoked potential (MEP), intracortical inhibition (ICI) and facilitation (ICF), short- and long-latency afferent inhibition (SAI and LAI) in the conditioned M1. The 5 Hz rPAS_25ms protocol but not the 5 Hz rPAS10_ms protocol caused a somatotopically specific increase in mean MEP amplitudes in the relaxed APB muscle. The 5 Hz rPAS_25ms protocol also led to a loss of SAI, but there was no correlation between individual changes in SAI and corticospinal excitability. These after-effects were still present 6 h after 5 Hz rPAS_25ms. There was no consistent effect on ICI, ICF and LAI. The 5 Hz rENS and 5 Hz rTMS protocols failed to induce any change in corticospinal excitability when given alone. These findings show that 2 min of 5 Hz rPAS_25ms produce a long-lasting and somatotopically specific increase in corticospinal excitability, presumably by sensorimotor disinhibition.

(Received 23 May 2006; accepted after revision 26 June 2006; first published online 6 July 2006)
Corresponding author A. Quartarone: Clinica Neurologica 2, Policlinico Universitario, 98125 Messina, Italy. Email: angelo.quartarone{at}unime.it

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