Experimental Brain Research

, Volume 121, Issue 2, pp 145–152

Localizing the site of magnetic brain stimulation by functional MRI

  • Y. Terao
  • Yoshikazu Ugawa
  • Katsuyuki Sakai
  • Satoru Miyauchi
  • Hideki Fukuda
  • Yuka Sasaki
  • Ryouichi Takino
  • Ritsuko Hanajima
  • Toshiaki Furubayashi
  • Benno Pütz
  • Ichiro Kanazawa
RESEARCH ARTICLE

DOI: 10.1007/s002210050446

Cite this article as:
Terao, Y., Ugawa, Y., Sakai, K. et al. Exp Brain Res (1998) 121: 145. doi:10.1007/s002210050446

Abstract 

In order to locate the site of action of transcranial magnetic stimulation (TMS) within the human motor cortices, we investigated how the optimal positions for evoking motor responses over the scalp corresponded to the hand and leg primary-motor areas. TMS was delivered with a figure-8 shaped coil over each point of a grid system constructed on the skull surface, each separated by 1 cm, to find the optimal site for obtaining motor-evoked potentials (MEPs) in the contralateral first dorsal interosseous (FDI) and tibialis anterior (TA) muscles. Magnetic resonance imaging scans of the brain were taken for each subject with markers placed over these sites, the positions of which were projected onto the cortical region just beneath. On the other hand, cortical areas where blood flow increased during finger tapping or leg movements were identified on functional magnetic resonance images (fMRI), which should include the hand and leg primary-motor areas. The optimal location for eliciting MEPs in FDI, regardless of their latency, lay just above the bank of the precentral gyrus, which coincided with the activated region during finger tapping in fMRI studies. The direction of induced current preferentially eliciting MEPs with the shortest latency in each subject was nearly perpendicular to the course of the precentral gyrus at this position. The optimal site for evoking motor responses in TA was also located just above the activated area during leg movements identified within the anterior portion of the paracentral lobule. The results suggest that, for magnetic stimulation, activation occurs in the primary hand and leg motor area (Brodmann area 4), which is closest in distance to the optimal scalp position for evoking motor responses.

Key words Transcranial magnetic stimulationFunctional magnetic resonance imagingMotor cortex Central sulcusD wave

Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • Y. Terao
    • 1
  • Yoshikazu Ugawa
    • 1
  • Katsuyuki Sakai
    • 1
  • Satoru Miyauchi
    • 2
  • Hideki Fukuda
    • 3
  • Yuka Sasaki
    • 2
  • Ryouichi Takino
    • 2
  • Ritsuko Hanajima
    • 1
  • Toshiaki Furubayashi
    • 1
  • Benno Pütz
    • 2
  • Ichiro Kanazawa
    • 1
  1. 1.Department of Neurology, Tokyo University Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan Tel.: +81-3-3815-5411 Ext. 3790, Fax: +81-3-5800-6548JP
  2. 2.Communications Research Laboratory, Tokyo, JapanJP
  3. 3.Department of Industrial Physiology, National Institute of Industrial Health, Kawasaki, JapanJP