Direct and indirect activation of human corticospinal neurons by transcranial magnetic and electrical stimulation

Neurosci Lett. 1996 May 24;210(1):45-8. doi: 10.1016/0304-3940(96)12659-8.


Corticospinal volleys and surface electromyographic (EMG) responses evoked by magnetic and electrical transcranial stimulation were recorded simultaneously in three conscious human subjects. For magnetic stimulation, the figure-of-eight coil was held on the hand motor area either with the induced current through the brain flowing in a postero-anterior direction (P-A stimulation) or in a latero-medial direction (L-M stimulation). For electrical stimulation, the anode was placed 7 cm lateral to the vertex and cathode at the vertex (anodal stimulation). The P-A stimulation that was generally used preferentially evoked I waves, whereas the L-M and anodal stimulation preferentially evoked D wave. The results suggested that the mode of activation by transcranial magnetic stimulation altered, depending on its current direction, and the difference between P-M magnetic and electrical stimulation can be explained by the context of the D and I hypothesis.

MeSH terms

  • Aged
  • Electric Stimulation
  • Female
  • Humans
  • Magnetics
  • Male
  • Middle Aged
  • Neurons / physiology*
  • Pyramidal Tracts / cytology*