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Differences in after-effect between monophasic and biphasic high-frequency rTMS of the human motor cortex.
Clin Neurophysiol. 2007 Oct; 118(10):2227-33.CN

Abstract

OBJECTIVE

To study differences in the long-term after-effect between high-frequency, monophasic and biphasic repetitive transcranial magnetic stimulation (rTMS).

METHODS

Ten hertz rTMS was delivered over the left primary motor cortex and motor evoked potentials (MEPs) were recorded from the right first dorsal interosseous muscle. To probe motor cortex excitability we recorded MEPs at several timings before, during and after several types of conditioning rTMSs. We also recorded F-waves to probe spinal excitability changes. Thousand pulses were given in total, with a train of 10 Hz, 100 pulses delivered every minute (ten trains for 10min). The intensity was fixed at 90% active motor threshold (AMT) or 90% resting motor threshold (RMT) for both monophasic and biphasic rTMS. In addition, we performed a monophasic rTMS experiment using a fixed intensity of 90% RMT for biphasic pulses.

RESULTS

At 90% AMT, MEPs were enhanced for a few minutes after both monophasic and biphasic rTMS. On the other hand, at 90% RMT, a larger and longer enhancement of MEPs was evoked after monophasic rTMS than after biphasic rTMS. Monophasic rTMS at an intensity adjusted to biphasic 90% RMT elicited a great enhancement similar to that after monophasic rTMS at monophasic 90% RMT. Neither F-wave amplitude nor its occurrence rate was significantly altered by 90% RMT monophasic rTMS.

CONCLUSIONS

These results suggest that enhancement after rTMS occurs at the motor cortex. Monophasic rTMS has a stronger after-effect on motor cortical excitability than biphasic rTMS. This is probably because monophasic pulses preferentially activate a relatively uniform population of neurons oriented in the same direction and their effects summate more readily than biphasic rTMS activating differently oriented neurons at slight different timings altogether.

SIGNIFICANCE

The present results suggest that when using rTMS as a therapeutic tool or in research fields, the waveforms of magnetic pulses may affect the results profoundly.

Authors+Show Affiliations

Department of Neurology, Division of Neuroscience, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. araino@hotmail.comNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

17765606

Citation

Arai, Noritoshi, et al. "Differences in After-effect Between Monophasic and Biphasic High-frequency rTMS of the Human Motor Cortex." Clinical Neurophysiology : Official Journal of the International Federation of Clinical Neurophysiology, vol. 118, no. 10, 2007, pp. 2227-33.
Arai N, Okabe S, Furubayashi T, et al. Differences in after-effect between monophasic and biphasic high-frequency rTMS of the human motor cortex. Clin Neurophysiol. 2007;118(10):2227-33.
Arai, N., Okabe, S., Furubayashi, T., Mochizuki, H., Iwata, N. K., Hanajima, R., Terao, Y., & Ugawa, Y. (2007). Differences in after-effect between monophasic and biphasic high-frequency rTMS of the human motor cortex. Clinical Neurophysiology : Official Journal of the International Federation of Clinical Neurophysiology, 118(10), 2227-33.
Arai N, et al. Differences in After-effect Between Monophasic and Biphasic High-frequency rTMS of the Human Motor Cortex. Clin Neurophysiol. 2007;118(10):2227-33. PubMed PMID: 17765606.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Differences in after-effect between monophasic and biphasic high-frequency rTMS of the human motor cortex. AU - Arai,Noritoshi, AU - Okabe,Shingo, AU - Furubayashi,Toshiaki, AU - Mochizuki,Hitoshi, AU - Iwata,Nobue K, AU - Hanajima,Ritsuko, AU - Terao,Yasuo, AU - Ugawa,Yoshikazu, Y1 - 2007/08/31/ PY - 2006/12/27/received PY - 2007/07/04/revised PY - 2007/07/05/accepted PY - 2007/9/4/pubmed PY - 2007/12/6/medline PY - 2007/9/4/entrez SP - 2227 EP - 33 JF - Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology JO - Clin Neurophysiol VL - 118 IS - 10 N2 - OBJECTIVE: To study differences in the long-term after-effect between high-frequency, monophasic and biphasic repetitive transcranial magnetic stimulation (rTMS). METHODS: Ten hertz rTMS was delivered over the left primary motor cortex and motor evoked potentials (MEPs) were recorded from the right first dorsal interosseous muscle. To probe motor cortex excitability we recorded MEPs at several timings before, during and after several types of conditioning rTMSs. We also recorded F-waves to probe spinal excitability changes. Thousand pulses were given in total, with a train of 10 Hz, 100 pulses delivered every minute (ten trains for 10min). The intensity was fixed at 90% active motor threshold (AMT) or 90% resting motor threshold (RMT) for both monophasic and biphasic rTMS. In addition, we performed a monophasic rTMS experiment using a fixed intensity of 90% RMT for biphasic pulses. RESULTS: At 90% AMT, MEPs were enhanced for a few minutes after both monophasic and biphasic rTMS. On the other hand, at 90% RMT, a larger and longer enhancement of MEPs was evoked after monophasic rTMS than after biphasic rTMS. Monophasic rTMS at an intensity adjusted to biphasic 90% RMT elicited a great enhancement similar to that after monophasic rTMS at monophasic 90% RMT. Neither F-wave amplitude nor its occurrence rate was significantly altered by 90% RMT monophasic rTMS. CONCLUSIONS: These results suggest that enhancement after rTMS occurs at the motor cortex. Monophasic rTMS has a stronger after-effect on motor cortical excitability than biphasic rTMS. This is probably because monophasic pulses preferentially activate a relatively uniform population of neurons oriented in the same direction and their effects summate more readily than biphasic rTMS activating differently oriented neurons at slight different timings altogether. SIGNIFICANCE: The present results suggest that when using rTMS as a therapeutic tool or in research fields, the waveforms of magnetic pulses may affect the results profoundly. SN - 1388-2457 UR - https://www.unboundmedicine.com/medline/citation/17765606/Differences_in_after_effect_between_monophasic_and_biphasic_high_frequency_rTMS_of_the_human_motor_cortex_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S1388-2457(07)00368-9 DB - PRIME DP - Unbound Medicine ER -