HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 96/3/1337    most recent 01140.2005v1 Alert me when this article is cited Alert me if a correction is posted Citation Map 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 Web of Science (9) Citing Articles via Google Scholar Google Scholar Articles by Kujirai, K. Articles by Rothwell, J. C. Search for Related Content PubMed PubMed Citation Articles by Kujirai, K. Articles by Rothwell, J. C.

Associative Plasticity in Human Motor Cortex During Voluntary Muscle Contraction

¹Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark; and ²Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College of London, London, United Kingdom

Submitted 20 October 2005; accepted in final form 16 May 2006

TMS pulses over the hand area of motor cortex activate different subpopulations of synaptic connections if the direction of the induced current in the brain is reversed from posterior-anterior (PA) direction to anterior-posterior (AP). We tested whether this also made a difference to the after-effects of paired associative stimulation (PAS: ulnar nerve stimulation followed 25 ms later by a transcranial magnetic stimulation pulse). If 50 pairs of stimuli (0.1 Hz) were applied using conventional suprathreshold PA-PAS in resting subjects, there was no effect on motor-evoked potentials (MEPs) in the first dorsal interosseous muscle. In contrast if the same number of pulses were given while subjects made a small tonic (5% maximum) contraction, MEPs were facilitated and resting motor threshold reduced when AP but not PA pulses were used. Subsequent experiments employed subthreshold TMS (95% of the active motor threshold) during voluntary muscle contraction. MEP facilitation accompanied by reduced AP threshold occurred when PAS was given using AP pulses (AP-Sub-PAS), whereas PAS using PA pulses (PA-Sub-PAS) had no excitatory effect. There was no facilitation if the ulnar nerve stimulus was replaced by digital nerve stimulation. There was a tendency for short interval intracortical inhibition (SICI) to decrease and intracortical facilitation (ICF) to increase after AP-Sub-PAS. We propose that the increased effectiveness of AP-Sub-PAS over PA-Sub-PAS is due to the fact that AP TMS more readily activates I3 inputs to corticospinal neurons and hence that these are an important component of associative plasticity in the human motor cortex.

This article has been cited by other articles:

				P. Jung and U. Ziemann Homeostatic and Nonhomeostatic Modulation of Learning in Human Motor Cortex J. Neurosci., April 29, 2009; 29(17): 5597 - 5604. [Abstract] [Full Text] [PDF]

				V. Di Lazzaro, M. Dileone, F. Pilato, P. Profice, A. Oliviero, P. Mazzone, A. Insola, F. Capone, F. Ranieri, and P.A. Tonali Associative Motor Cortex Plasticity: Direct Evidence in Humans Cereb Cortex, January 28, 2009; (2009) bhn255v1. [Abstract] [Full Text] [PDF]

				M. V. Sale, M. C. Ridding, and M. A. Nordstrom Cortisol Inhibits Neuroplasticity Induction in Human Motor Cortex J. Neurosci., August 13, 2008; 28(33): 8285 - 8293. [Abstract] [Full Text] [PDF]

				J. Reis, O. B. Swayne, Y. Vandermeeren, M. Camus, M. A. Dimyan, M. Harris-Love, M. A. Perez, P. Ragert, J. C. Rothwell, and L. G. Cohen Contribution of transcranial magnetic stimulation to the understanding of cortical mechanisms involved in motor control J. Physiol., January 15, 2008; 586(2): 325 - 351. [Abstract] [Full Text] [PDF]

				F. D. Roy, J. A. Norton, and M. A. Gorassini Role of Sustained Excitability of the Leg Motor Cortex After Transcranial Magnetic Stimulation in Associative Plasticity J Neurophysiol, August 1, 2007; 98(2): 657 - 667. [Abstract] [Full Text] [PDF]

				S. Meunier, H. Russmann, M. Simonetta-Moreau, and M. Hallett Changes in Spinal Excitability After PAS J Neurophysiol, April 1, 2007; 97(4): 3131 - 3135. [Abstract] [Full Text] [PDF]

				N. Mrachacz-Kersting, M. Fong, B. A. Murphy, and T. Sinkjaer Changes in Excitability of the Cortical Projections to the Human Tibialis Anterior After Paired Associative Stimulation J Neurophysiol, March 1, 2007; 97(3): 1951 - 1958. [Abstract] [Full Text] [PDF]