Preconditioning Repetitive Transcranial Magnetic Stimulation of Premotor Cortex Can Reduce But Not Enhance Short-Term Facilitation of Primary Motor Cortex

• Published in: Journal of neurophysiology 2008-02, Vol.99 (2), p.564-570
• Main Authors: Suppa, A, Bologna, M, Gilio, F, Lorenzano, C, Rothwell, J. C, Berardelli, A
• Format: Article
• Language: English
• Subjects: Adult; Analysis of Variance; Conditioning (Psychology); Dose-Response Relationship, Radiation; Electric Stimulation - methods; Electromyography - methods; Evoked Potentials, Motor - physiology; Evoked Potentials, Motor - radiation effects; Female; Humans; Male; Motor Cortex - physiology; Muscle, Skeletal - physiology; Muscle, Skeletal - radiation effects; Reaction Time - physiology; Reaction Time - radiation effects; Time Factors; Transcranial Magnetic Stimulation
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00753.2007

1 Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, United Kingdom; 2 Department of Neurological Sciences and 3 Neuromed Institute, University of Rome "La Sapienza," Rome, Italy Submitted 6 July 2007; accepted in final form 3 December 2007 Short trains of suprathreshold 5-Hz repetitive transcranial magnetic stimulation (rTMS) over primary motor cortex (M1) evoke motor potentials (MEPs) in hand muscles that progressively increase in amplitude via a mechanism that is thought to be similar to short-term potentiation described in animal preparations. Long trains of subthreshold rTMS over dorsal premotor cortex (PMd) are known to affect the amplitude of single-pulse MEPs evoked from M1. We tested whether PMd-rTMS affects short-term facilitation in M1. We also explored the effect of PMd-rTMS on M1 responses evoked by single-pulse TMS of different polarities. We tested in 15 healthy subjects short-term facilitation in left M1 (10 suprathreshold TMS pulses at 5 Hz) after applying rTMS to left PMd (1,500 subthreshold pulses at 1 and 5 Hz). In a sample of subjects we delivered single-pulse TMS with different polarities and paired-pulse TMS at short intervals (SICI) after PMd-rTMS. Short-term facilitation in M1 was reduced after applying 1 Hz to PMd, but was unaffected after 5-Hz PMd-rTMS. PMd-rTMS with 1 Hz reduced the amplitude of MEPs evoked by monophasic posteroanterior (PA) or biphasic anteroposterior (AP)–PA but had little effect on MEPs by monophasic AP or biphasic PA–AP single-pulse TMS. PMd-rTMS left SICI unchanged. PMd-rTMS (1 Hz) reduces short-term facilitation in M1 induced by short 5-Hz trains. This effect is likely to be caused by reduced facilitation of I-wave inputs to corticospinal neurons. Address for reprint requests and other correspondence: A. Berardelli, Dipartimento Scienze Neurologiche, Università di Roma "La Sapienza," Viale dell'Università, 30, 00185 Rome, Italy (E-mail: alfredo.berardelli{at}uniroma1.it )