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Effects of coil orientation and magnetic field shield on transcranial magnetic stimulation in cats
Author(s) -
Nakatoh Shinichi,
Kitagawa Hideki,
Kawaguchi Yoshiharu,
Nakamura Hiroshi,
Takano Haruo,
Tsuji Haruo
Publication year - 1998
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/(sici)1097-4598(199809)21:9<1172::aid-mus8>3.0.co;2-4
Subject(s) - transcranial magnetic stimulation , electromagnetic coil , magnetic field , cats , orientation (vector space) , nuclear magnetic resonance , stimulation , shield , medicine , neuroscience , physics , psychology , biology , geometry , mathematics , quantum mechanics , paleontology
To obtain suitable stimulus conditions for transcranial magnetic stimulation, the evoked compound muscle action potential (ECMAP), evoked spinal cord potential (ESCP), and magnetic and electric fields were analyzed in cats with and without the use of a magnetic field shield. Cats were stimulated using a figure 8 magnetic coil placed on the cranium above the motor cortex. The maximum ECMAP amplitude was recorded when the electric current in the coil was in the mediolateral direction, regardless of whether a magnetic shield with a 5 × 5 cm window was used. ECMAP and ESCP thresholds were reduced when magnetic shielding was in place. Due to the edge effect, the strengths of the magnetic and electric fields were highest in the brainstem area, which is an inhomogeneous volume conductor of the cat's cranium. A large induced electric field directed caudally elicited ECMAP and ESCP responses effectively when a magnetic shield with a 5 × 5 cm window was in place. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21: 1172–1180, 1998.