Three trials of transcranial magnetic stimulation (TMS) during the maximum voluntary muscle contraction (MVC) were repeated at 15-minute intervals for 1 hour to examine the effects on motor evoked potentials (MEPs) in the digital muscles and pinching muscle force before and after 4 high-intensity TMSs (test 1 condition) or sham TMS (test 2 condition) with MVC. Under the placebo condition, real TMS with MVC was administered only before and 1 hour after the sham TMS with MVC. Magnetic stimulation at the foramen magnum level (FMS) with MVC was performed by the same protocol as that for the test 2 condition. As a result, MEP sizes in the digital muscles significantly increased after TMS with MVC under test conditions compared with the placebo conditions ( ). Pinching muscle force was significantly larger 45 minutes and 1 hour after TMS with MVC under the test conditions than under the placebo condition ( ). FMS significantly decreased MEP amplitudes 60 minutes after the sham TMS with MVC ( ). The present results suggest that intermittently repeated TMS with MVC facilitates motor neuron excitabilities and muscle force. However, further studies are needed to confirm the effects of TMS with MVC and its mechanism. 1. Introduction Transcranial magnetic stimulation (TMS) is a noninvasive method of stimulating cortical neurons; that is, electrical currents in axons of interneurons stimulated by TMS activate cortical neuron cell bodies via synaptic transmission [1]. Single TMS or repetitive TMS (rTMS) can transiently inhibit or facilitate cortical neuron excitabilities for a prolonged period following stimulation [2–5]. According to these lines of evidence, many studies have tested whether TMSs or rTMS accelerates functional recovery in patients with motor disability [6–11]. A previous study reported that only three single TMS during the maximum voluntary muscle contraction (MVC) in patients with weakness of the thigh muscles transiently, but significantly, enhanced muscle strength compared with TMS during muscle relaxation [12]. Nevertheless, the effects of TMS with MVC have not yet been established, and its mechanism still remains unknown. In the present study, we investigated the effects of TMS with MVC on motor neuron excitability by recording motor evoked potentials (MEPs) with MVC, using a modified protocol of TMS with MVC to induce more prolonged and robust effects on motor neuron function. Furthermore, we stimulated the corticospinal tract at the foramen magnum level to detect the functional mechanism of TMS with MVC. Preliminary results of the present
References
[1]
A. T. Barker, “An introduction to the basic principles of magnetic nerve stimulation,” Journal of Clinical Neurophysiology, vol. 8, no. 1, pp. 26–37, 1991.
[2]
R. Chen, J. Classen, C. Gerloff et al., “Depression of motor cortex excitability by low-frequency transcranial magnetic stimulation,” Neurology, vol. 48, no. 5, pp. 1398–1403, 1997.
[3]
T. Kujirai, M. D. Caramia, J. C. Rothwell et al., “Corticocortical inhibition in human motor cortex,” Journal of Physiology, vol. 471, pp. 501–519, 1993.
[4]
A. Pascual-Leone, J. Valls-Sole, E. M. Wassermann, and M. Hallett, “Responses to rapid-rate transcranial magnetic stimulation of the human motor cortex,” Brain, vol. 117, no. 4, pp. 847–858, 1994.
[5]
T. Touge, W. Gerschlager, P. Brown, and J. C. Rothwell, “Are the after-effects of low-frequency rTMS on motor cortex excitability due to changes in the efficacy of cortical synapses?” Clinical Neurophysiology, vol. 112, no. 11, pp. 2138–2145, 2001.
[6]
M. L. Harris-Love and L. G. Cohen, “Noninvasive cortical stimulation in neurorehabilitation: a review,” Archives of Physical Medicine and Rehabilitation, vol. 87, no. 12, supplement, pp. S84–S93, 2006.
[7]
J. P. Lefaucheur, “Stroke recovery can be enhanced byusing repetitive transcranial magnetic stimulation (rTMS),” Neurophysiologie Clinique, vol. 36, no. 3, pp. 105–115, 2006.
[8]
J. Málly and T. W. Stone, “New advances in the rehabilitation of CNS diseases applying rTMS,” Expert Review of Neurotherapeutics, vol. 7, no. 2, pp. 165–177, 2007.
[9]
P. Profice, F. Pilato, M. Dileone et al., “Use of transcranial magnetic stimulation of the brain in stroke rehabilitation,” Expert Review of Neurotherapeutics, vol. 7, no. 3, pp. 249–258, 2007.
[10]
S. Rossi and P. M. Rossini, “TMS in cognitive plasticity and the potential for rehabilitation,” Trends in Cognitive Sciences, vol. 8, no. 6, pp. 273–279, 2004.
[11]
D. Urbach, A. Berth, and F. Awiszus, “Effect of transcranial magnetic stimulation on voluntary activation in patients with quadriceps weakness,” Muscle and Nerve, vol. 32, no. 2, pp. 164–169, 2005.
[12]
D. Urbach and F. Awiszus, “Stimulus strength related effect of transcranial magnetic stimulation on maximal voluntary contraction force of human quadriceps femoris muscle,” Experimental Brain Research, vol. 142, no. 1, pp. 25–31, 2002.
[13]
P. M. Rossini, A. T. Barker, A. Berardelli et al., “Non-invasive electrical and magnetic stimulation of the brain, spinal cord and roots: basic principles and procedures for routine clinical application. Report of an IFCN committee,” Electroencephalography and Clinical Neurophysiology, vol. 91, no. 2, pp. 79–92, 1994.
[14]
Y. Ugawa, Y. Uesaka, Y. Terao, R. Hanajima, and I. Kanazawa, “Magnetic stimulation of corticospinal pathways at the foramen magnum level in humans,” Annals of Neurology, vol. 36, no. 4, pp. 618–624, 1994.
[15]
D. R. McKay, M. C. Ridding, P. D. Thompson, and T. S. Miles, “Induction of persistent changes in the organisation of the human motor cortex,” Experimental Brain Research, vol. 143, no. 3, pp. 342–349, 2002.
[16]
K. Stefan, E. Kunesch, L. G. Cohen, R. Benecke, and J. Classen, “Induction of plasticity in the human motor cortex by paired associative stimulation,” Brain, vol. 123, no. 3, pp. 572–584, 2000.
[17]
K. Stefan, E. Kunesch, R. Benecke, L. G. Cohen, and J. Classen, “Mechanisms of enhancement of human motor cortex excitability induced by interventional paired associative stimulation,” Journal of Physiology, vol. 543, no. 2, pp. 699–708, 2002.
[18]
M. C. Ridding and J. L. Taylor, “Mechanisms of motor-evoked potential facilitation following prolonged dual peripheral and central stimulation in humans,” Journal of Physiology, vol. 537, no. 2, pp. 623–631, 2001.
[19]
M. C. Ridding, D. R. McKay, P. D. Thompson, and T. S. Miles, “Changes in corticomotor representations induced by prolonged peripheral nerve stimulation in humans,” Clinical Neurophysiology, vol. 112, no. 8, pp. 1461–1469, 2001.
[20]
A. B. Conforto, A. Kaelin-Lang, and L. G. Cohen, “Increase in hand muscle strength of stroke patients after somatosensory stimulation,” Annals of Neurology, vol. 51, no. 1, pp. 122–125, 2002.
[21]
C. M. Bütefisch, V. Khurana, L. Kopylev, and L. G. Cohen, “Enhancing encoding of a motor memory in the primary motor cortex by cortical stimulation,” Journal of Neurophysiology, vol. 91, no. 5, pp. 2110–2116, 2004.
[22]
D. O. Hebb, The Organization of Behavior. A Neuropsychological Theory, John Wiley & Sons, New York, NY, USA, 1949.
[23]
K. R. Mills, Magnetic Stimulation of the Human Nervous System, Oxford University Press, New York, NY, USA, 1999.
[24]
K. J. Werhahn, J. Taylor, M. Ridding, B. U. Meyer, and J. C. Rothwell, “Effect of transcranial magnetic stimulation over the cerebellum on the excitability of human motor cortex,” Electroencephalography and Clinical Neurophysiology, vol. 101, no. 1, pp. 58–66, 1996.
[25]
W. Gerschlager, L. O. D. Christensen, S. Bestmann, and J. C. Rothwell, “rTMS over the cerebellum can increase corticospinal excitability through a spinal mechanism involving activation of peripheral nerve fibres,” Clinical Neurophysiology, vol. 113, no. 9, pp. 1435–1440, 2002.
[26]
M. Oliveri, G. Koch, S. Torriero, and C. Caltagirone, “Increased facilitation of the primary motor cortex following 1 Hz repetitive transcranial magnetic stimulation of the contralateral cerebellum in normal humans,” Neuroscience Letters, vol. 376, no. 3, pp. 188–193, 2005.
[27]
J. L. Taylor, G. M. Allen, J. E. Butler, and S. C. Gandevia, “Supraspinal fatigue during intermittent maximal voluntary contractions of the human elbow flexors,” Journal of Applied Physiology, vol. 89, no. 1, pp. 305–313, 2000.
[28]
J. L. Taylor, J. E. Butler, and S. C. Gandevia, “Altered responses of human elbow flexors to peripheral-nerve and cortical stimulation during a sustained maximal voluntary contraction,” Experimental Brain Research, vol. 127, no. 1, pp. 108–115, 1999.
