Modulation of Effects of Intermittent Theta Burst Stimulation Applied Over Primary Motor Cortex (M1) by Conditioning Stimulation of the Opposite M1

1 Human Cortical Physiology and Stroke Neurorehabilitation Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland; 2 Department of Cognitive Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; and 3 Ne...

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Published in:Journal of neurophysiology 2009-08, Vol.102 (2), p.766-773
Main Authors: Ragert, Patrick, Camus, Mickael, Vandermeeren, Yves, Dimyan, Michael A, Cohen, Leonardo G
Format: Article
Language:English
Subjects:
Adult
Attention - physiology
Evoked Potentials, Motor - physiology
Fatigue - physiopathology
Female
Functional Laterality - physiology
Hand - physiology
Hand Strength - physiology
Humans
Male
Motor Activity - physiology
Motor Cortex - physiology
Neuronal Plasticity - physiology
Pain - physiopathology
Reaction Time - physiology
Spinal Cord - physiology
Time Factors
Transcranial Magnetic Stimulation
Young Adult
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Summary:1 Human Cortical Physiology and Stroke Neurorehabilitation Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland; 2 Department of Cognitive Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; and 3 Neurology Department, Cliniques universitaires, Université catholique de Louvain de Mont-Godinne, Yvoir, Belgium Submitted 27 March 2009; accepted in final form 21 May 2009 The excitability of the human primary motor cortex (M1) as tested with transcranial magnetic stimulation (TMS) depends on its previous history of neural activity. Homeostatic plasticity might be one important physiological mechanism for the regulation of corticospinal excitability and synaptic plasticity. Although homeostatic plasticity has been demonstrated locally within M1, it is not known whether priming M1 could result in similar homeostatic effects in the homologous M1 of the opposite hemisphere. Here, we sought to determine whether down-regulating excitability (priming) in the right (R) M1 with 1-Hz repetitive transcranial magnetic stimulation (rTMS) changes the excitability-enhancing effect of intermittent theta burst stimulation (iTBS) applied over the homologous left (L) M1. Subjects were randomly allocated to one of four experimental groups in a sham-controlled parallel design with real or sham R M1 1-Hz TMS stimulation always preceding L M1 iTBS or sham by about 10 min. The primary outcome measure was corticospinal excitability in the L M1, as measured by recruitment curves (RCs). Secondary outcome measures included pinch force, simple reaction time, and tapping speed assessed in the right hand. The main finding of this study was that preconditioning R M1 with 1-Hz rTMS significantly decreased the excitability-enhancing effects of subsequent L M1 iTBS on RCs. Application of 1-Hz rTMS over R M1 alone and iTBS over L M1 alone resulted in increased RC in L M1 relative to sham interventions. The present findings are consistent with the hypothesis that homeostatic mechanisms operating across hemispheric boundaries contribute to regulate motor cortical function in the primary motor cortex. Address for reprint requests and other correspondence: L. G. Cohen, Human Cortical Physiology and Stroke Neurorehabilitation Section, NINDS, NIH, Bethesda, MD 20817 (E-mail: cohenl{at}ninds.nih.gov )
ISSN:0022-3077
1522-1598
DOI:10.1152/jn.00274.2009