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I-Waves in Motor Cortex

Ziemann, Ulf*; Rothwell, John C.

Journal of Clinical Neurophysiology: July 2000 - Volume 17 - Issue 4 - p 397-405
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Summary I-waves refer to high-frequency (approximately 600 Hz) repetitive discharge of corticospinal fibers produced by single-pulse stimulation of the motor cortex. First detected in animal preparations, this multiple discharge can also be recorded in humans with epidural electrodes over the spinal cord, and with recently developed noninvasive paired-pulse transcranial magnetic stimulation protocols. The exact nature of the generation of I-waves is still unclear, but there is convincing evidence that they originate in the motor cortex, mainly through activation of corticocortical projections onto corticospinal neurons. The ability to measure I-waves in human motor cortex allows one to test the integrity and excitability of the underlying corticocortical circuits in health and disease.

*Clinic of Neurology, J.W. Goethe-University of Frankfurt, Germany, and †Human Movement and Balance Unit, The Institute of Neurology, Queen Square, London, United Kingdom

Address correspondence and reprint requests to Dr. Ulf Ziemann, Clinic of Neurology, J.W. Goethe, University of Frankfurt, Theodor- Stern-Kai 7, D-60590 Frankfurt am Main, Germany.

Copyright © 2000 American Clinical Neurophysiology Society