Transcranial electric and magnetic stimulation of the leg area of the human motor cortex: single motor unit and surface EMG responses in the tibialis anterior muscle

A. Priori, L. Bertolasi, D. Dressler, J. C. Rothwell, B. L. Day, P. D. Thompson, C. D. Marsden

Research output: Contribution to journalArticlepeer-review

Abstract

We compared single motor unit and surface EMG responses in the active right tibialis anterior following anodal electrical or magnetic stimulation of the motor cortex over the vertex. Magnetic stimulation used a monophasic current pulse through a circular coil centred 3 cm anterior to the vertex. Lowest threshold magnetic stimulation occurred when the current in the coil flowed from the left to the right side at the posterior rim of the coil. Such stimulation produced single unit and surface EMG responses which had the same latency as those produced by anodal electric stimulation. If the direction of the magnetic stimulating current was reversed, response latencies became more variable from unit to unit, and on average they occurred 1.0 ± 0.5 msec later. In single motor units anodal and magnetic post-stimulus time histogram (PSTH) peaks had the same duration. This was similar to the duration of the PSTH peaks produced by a single low intensity stimulus given to the common peroneal nerve. We conclude that magnetic stimulation can produce direct activation of corticospinal neurones to the tibialis anterior if the direction of induced current flow is optimal. This projection is likely to be either monosynaptic or oligosynaptic.

Original languageEnglish
Pages (from-to)131-137
Number of pages7
JournalElectroencephalography and Clinical Neurophysiology - Evoked Potentials
Volume89
Issue number2
DOIs
Publication statusPublished - 1993

Keywords

  • Motor cortex
  • Tibialis anterior
  • Transcranial electric stimulation
  • Transcranial magnetic stimulation

ASJC Scopus subject areas

  • Clinical Neurology
  • Neuroscience(all)

Fingerprint Dive into the research topics of 'Transcranial electric and magnetic stimulation of the leg area of the human motor cortex: single motor unit and surface EMG responses in the tibialis anterior muscle'. Together they form a unique fingerprint.

Cite this