Journal article

Repetitive activation of the corticospinal pathway by means of rTMS may reduce the efficiency of corticomotoneuronal synapses

  • Taube, Wolfgang Department of Medicine, Movement and Sport Science, University of Fribourg, Switzerland
  • Leukel, Christian Department of Medicine, Movement and Sport Science, University of Fribourg, Switzerland - Department of Sport Science, University of Freiburg, Germany
  • Nielsen, Jens Bo Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark - Department of Neuroscience and Pharmacology, University of Copenhagen, Denmark
  • Lundbye-Jensen, Jesper Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark - Department of Neuroscience and Pharmacology, University of Copenhagen, Denmark
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    09.01.2014
Published in:
  • Cerebral Cortex. - 2015, vol. 25, no. 6, p. 1629-1637
English Low-frequency rTMS applied to the primary motor cortex (M1) may produce depression of motor-evoked potentials (MEPs). This depression is commonly assumed to reflect changes in cortical circuits. However, little is known about rTMS-induced effects on subcortical circuits. Therefore, the present study aimed to clarify whether rTMS influences corticospinal transmission by altering the efficiency of corticomotoneuronal (CM) synapses. The corticospinal transmission to soleus α-motoneurons was evaluated through conditioning of the soleus H-reflex by magnetic stimulation of either M1 (M1-conditioning) or the cervicomedullary junction (CMS-conditioning). The first facilitation of the H-reflex (early facilitation) was determined after M1- and CMS-conditioning. Comparison of the early facilitation before and after 20-min low-frequency (1 Hz) rTMS revealed suppression with M1- (−17 ± 4%; P = 0.001) and CMS-conditioning (−6 ± 2%; P = 0.04). The same rTMS protocol caused a significant depression of compound MEPs, whereas amplitudes of H-reflex and M-wave remained unaffected, indicating a steady level of motoneuronal excitability. Thus, the effects of rTMS are likely to occur at a premotoneuronal site—either at M1 and/or the CM synapse. As the early facilitation reflects activation of direct CM projections, the most likely site of action is the synapse of the CM neurons onto spinal motoneurons.
Faculty
Faculté des sciences et de médecine
Department
Département de Médecine
Language
  • English
Classification
Biology
License
License undefined
Identifiers
Persistent URL
https://folia.unifr.ch/unifr/documents/303385
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