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Inter-hemispheric asymmetry of ipsilateral corticofugal projections to proximal muscles in humans

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Abstract

Motor evoked potentials (MEPs) elicited in many proximal or truncal muscles by ipsilateral transcranial magnetic stimulation (TMS) are thought to be mediated by an oligosynaptic corticofugal pathway and not by uncrossed corticospinal collaterals. In the present study, we compared the input–output properties and scalp surface topography of the ipsilateral and contralateral projections to pectoralis major (PM) and latissimus dorsi (LD) in seven healthy subjects. In six subjects, ipsilateral MEPs evoked by stimulation of one hemisphere (dominant ipsilateral hemisphere) were markedly larger in amplitude than the MEPs evoked in the opposite hemisphere (non-dominant ipsilateral hemisphere). The dominant ipsilateral hemisphere MEPs were significantly larger than the non-dominant MEPs (p<0.02) by an average factor of 3.6 and 3.4 times in PM and LD, respectively. Similarly, there was significant asymmetry between hemispheres in the scalp surface area from which ipsilateral MEPs could be evoked. In contrast, contralateral projections were symmetric in both MEP amplitude and area. Neither the right nor left hemisphere was consistently the dominant ipsilateral hemisphere. The ipsilateral centre of gravity (CoG) for PM was located an average of 0.8±0.6 cm posterior to the contralateral CoG, but no significant differences were observed between ipsilateral and contralateral CoGs in LD. These results demonstrate that the excitability of ipsilateral corticofugal projections to PM and LD are asymmetric between hemispheres.

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References

  • Benecke R, Meyer BU, Schonle P, Conrad B (1988) Transcranial magnetic stimulation of the human brain: responses in muscles supplied by cranial nerves. Exp Brain Res 71:623–632

    CAS  PubMed  Google Scholar 

  • Butler SL, Miles TS, Thompson PD, Nordstrom MA (2001) Task-dependent control of human masseter muscles from ipsilateral and contralateral motor cortex. Exp Brain Res 137:65–70

    CAS  PubMed  Google Scholar 

  • Carr LJ, Harrison LM, Stephens JA (1994) Evidence for bilateral innervation of certain homologous motoneurone pools in man. J Physiol 475:217–227

    CAS  PubMed  Google Scholar 

  • Classen J, Knorr U, Werhahn KJ, Schlaug G, Kunesch E, Cohen LG, Seitz RJ, Benecke R (1998) Multimodal output mapping of human central motor representation on different spatial scales. J Physiol 512:163–179

    CAS  PubMed  Google Scholar 

  • Colebatch JG, Rothwell JC, Day BL, Thompson PD, Marsden CD (1990) Cortical outflow to proximal arm muscles in man. Brain 113:1843–1856

    PubMed  Google Scholar 

  • Cruccu G, Berardelli A, Inghilleri M, Manfredi M (1989) Functional organization of the trigeminal motor system in man. A neurophysiological study. Brain 112:1333–1350

    PubMed  Google Scholar 

  • Ferbert A, Caramia D, Priori A, Bertolasi L, Rothwell JC (1992) Cortical projection to erector spinae muscles in man as assessed by focal transcranial magnetic stimulation. Electroencephalogr Clin Neurophysiol 85:382–387

    Google Scholar 

  • Gandevia SC, Rothwell JC (1987) Activation of the human diaphragm from the motor cortex. J Physiol 384:109–118

    CAS  PubMed  Google Scholar 

  • Hamdy S, Rothwell JC (1998) Gut feelings about recovery after stroke: the organization and reorganization of human swallowing motor cortex. Trends Neurosci 21:278–282

    CAS  PubMed  Google Scholar 

  • Hamdy S, Aziz Q, Rothwell JC, Singh KD, Barlow J, Hughes DG, Tallis RC, Thompson DG (1996) The cortical topography of human swallowing musculature in health and disease. Nat Med 2:1217–1224

    CAS  PubMed  Google Scholar 

  • Kuypers H (1981) Anatomy of the descending pathways. In: Brookhart J, Mountcastle V (eds) Handbook of physiology, the nervous system, vol 2. American Physiological Society, Bethesda, pp 597–666

  • Maskill D, Murphy K, Mier A, Owen M, Guz A (1991) Motor cortical representation of the diaphragm in man. J Physiol 443:105–121

    CAS  PubMed  Google Scholar 

  • Plassman BL, Gandevia SC (1989) Comparison of human motor cortical projections to abdominal muscles and intrinsic muscles of the hand. Exp Brain Res 78:301–308

    CAS  PubMed  Google Scholar 

  • Quartarone A, MacKinnon CD, Rothwell JC (1999) Ipsilateral EMG responses in pectoralis major evoked by transcranial magnetic stimulation over the motor cortex. J Physiol 520P: 92P

    Google Scholar 

  • Thompson ML, Thickbroom GW, Mastaglia FL (1997) Corticomotor representation of the sternocleidomastoid muscle. Brain 120:245–255

    Article  PubMed  Google Scholar 

  • Tunstill S, Wynn-Davies A, Nowicky A, McGregor A, Davey N (2001) Corticospinal facilitation studied during voluntary contraction of human abdominal muscles. Exp Physiol 86:131–136

    Article  CAS  PubMed  Google Scholar 

  • Wassermann EM, Pascual-Leone A, Hallett M (1994) Cortical motor representation of the ipsilateral hand and arm. Exp Brain Res 100:121–132

    PubMed  Google Scholar 

  • Ziemann U, Ishii K, Borgheresi A, Yaseen Z, Battaglia F, Hallett M, Cincotta M, Wassermann EM (1999) Dissociation of the pathways mediating ipsilateral and contralateral motor-evoked potentials in human hand and arm muscles. J Physiol 518:895–906

    CAS  PubMed  Google Scholar 

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Acknowledgements

Colum D. MacKinnon was supported by a fellowship from the Heart and Stroke Foundation of Canada. We thank Mr. Peter Asselman for technical assistance with the experiments and Susan Schwerin for careful review of the manuscript.

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Correspondence to Colum D. MacKinnon.

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MacKinnon, C.D., Quartarone, A. & Rothwell, J.C. Inter-hemispheric asymmetry of ipsilateral corticofugal projections to proximal muscles in humans. Exp Brain Res 157, 225–233 (2004). https://doi.org/10.1007/s00221-004-1836-y

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