| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Received May 27, 2004
Revised June 22, 2004
Accepted after revision August 25, 2004
1 The University of Queensland
2 University of Queenland
3 The University of Auckland
* To whom correspondence should be addressed. E-mail: richard{at}hms.uq.edu.au.
Rhythmic movements brought about by the contraction of muscles on one side of the body give rise to phase-locked changes in the excitability of the homologous motor pathways of the opposite limb. Such crossed facilitation should favour patterns of bimanual coordination in which homologous muscles are engaged simultaneously, and disrupt those in which the muscles are activated in an alternating fashion. In order to examine these issues, we obtained responses to transcranial magnetic stimulation (TMS), to stimulation of the cervicomedullary junction (CMEPs), to peripheral nerve stimulation (H-reflexes and f-waves), and elicited stretch reflexes in the relaxed right flexor carpi radialis (FCR) muscle during rhythmic (2 Hz) flexion and extension movements of the opposite (left) wrist. The potentials evoked by TMS in right FCR were potentiated during the phases of movement in which the left FCR was most strongly engaged. In contrast, CMEPs were unaffected by the movements of the opposite limb. These results suggest that there was systematic variation of the excitability of the motor cortex ipsilateral to the moving limb. H-reflexes and stretch reflexes recorded in right FCR were modulated in phase with the activation of left FCR. As the f-waves did not vary in corresponding fashion, it appears that the phasic modulation of the H-reflex was mediated by presynaptic inhibition of Ia afferents. The observation that both H-reflexes and f-waves were depressed markedly during movements of the opposite indicates that there may also have been postsynaptic inhibition or disfacilitation of the largest motor units. Our findings indicate that the patterned modulation of excitability in motor pathways that occurs during rhythmic movements of the opposite limb is mediated primarily by interhemispheric interactions between cortical motor areas.
This article has been cited by other articles:
|
|
 |
|
  T. J. Carroll, M. Lee, M. Hsu, and J. Sayde Unilateral practice of a ballistic movement causes bilateral increases in performance and corticospinal excitability J Appl Physiol, June 1, 2008; 104(6): 1656 - 1664. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. M. Stinear, P. A. Barber, J. P. Coxon, M. K. Fleming, and W. D. Byblow Priming the motor system enhances the effects of upper limb therapy in chronic stroke Brain, May 1, 2008; 131(5): 1381 - 1390. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Maieron, G. D. Iannetti, J. Bodurka, I. Tracey, P. A. Bandettini, and C. A. Porro Functional Responses in the Human Spinal Cord during Willed Motor Actions: Evidence for Side- and Rate-Dependent Activity J. Neurosci., April 11, 2007; 27(15): 4182 - 4190. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. G. Carson, C. J. Smethurst, Y. Oytam, and A. de Rugy Postural Context Alters the Stability of Bimanual Coordination by Modulating the Crossed Excitability of Corticospinal Pathways J Neurophysiol, March 1, 2007; 97(3): 2016 - 2023. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. J. Carroll, R. D. Herbert, J. Munn, M. Lee, and S. C. Gandevia Contralateral effects of unilateral strength training: evidence and possible mechanisms J Appl Physiol, November 1, 2006; 101(5): 1514 - 1522. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Ridderikhoff, C. E. Peper, and P. J. Beek Unraveling Interlimb Interactions Underlying Bimanual Coordination J Neurophysiol, November 1, 2005; 94(5): 3112 - 3125. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
