Effects of voluntary contraction on descending volleys evoked by transcranial electrical stimulation over the motor cortex hand area in conscious humans

  • Di Lazzaro V
  • Restuccia D
  • Oliviero A
  • et al.
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Abstract

The spinal volleys evoked by electric anodal and cathodal stimulation over the cerebral motor cortex hand area were recorded from a bipolar electrode insert- ed into the cervical epidural space of two conscious hu- man subjects. We measured the size of volleys elicited by electric stimulation at active motor threshold and at 3% of maximum stimulator output above this value with subjects at rest and during maximum voluntary contrac- tion of the contralateral first dorsal interosseous muscle. Surface EMG activity was recorded at the same time. Electrical anodal stimulation evoked a single negative wave that we termed D-wave in analogy with data in ex- perimental animals. Cathodal stimulation evoked a single negative wave with a latency of 0.2 ms longer than the D-wave recruited by anodal stimulation. At both intensi- ties tested, voluntary contraction did not modify the am- plitude of the descending waves. We conclude that chang- es in cortical excitability induced by voluntary activity do not modify the corticospinal volley evoked by electric stimulation and that the D-waves evoked by both anodal and cathodal electric stimulation are probably initiated several nodes distant to the cell body.

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Di Lazzaro, V., Restuccia, D., Oliviero, A., Profice, P., Ferrara, L., Insola, A., … Rothwell, J. C. (1999). Effects of voluntary contraction on descending volleys evoked by transcranial electrical stimulation over the motor cortex hand area in conscious humans. Experimental Brain Research, 124, 525–528. https://doi.org/10.1007/s002210050649

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