Document Detail

Half sine, monophasic and biphasic transcranial magnetic stimulation of the human motor cortex.
MedLine Citation:
PMID:  16495145     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: To compare half sine transcranial magnetic stimuli (TMS) with conventional monophasic and biphasic stimuli, measuring resting and active motor threshold, motor evoked potential (MEP) input/output curve, MEP latency, and silent period duration. METHODS: We stimulated the dominant hand representation of the motor cortex in 12 healthy subjects utilising two different MagPro stimulators to generate TMS pulses of distinct monophasic, half sine and biphasic shape with anteriorly or posteriorly directed current flow. RESULTS: The markedly asymmetric monophasic pulse with a posterior current flow in the brain yielded a higher motor threshold, a less steep MEP input/output curve and a longer latency than all other TMS types. Similar but less pronounced results were obtained with a less asymmetric half sine pulses. The biphasic stimuli yielded the lowest motor threshold and a short latency, particularly with the posterior current direction. CONCLUSIONS: The more asymmetric the monophasic pulse, the stronger the difference to biphasic pulses. The 3rd and 4th quarter cycle of the biphasic waveform make it longer than any other waveform studied here and likely contribute to lowering motor threshold, shortening MEP latency and reversing the influence of current direction. SIGNIFICANCE: This systematic comparison of 3 waveforms and two current directions allows a better understanding of the mechanisms of TMS.
Martin Sommer; Aránzazu Alfaro; Milena Rummel; Sascha Speck; Nicolas Lang; Tobias Tings; Walter Paulus
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-02-21
Journal Detail:
Title:  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology     Volume:  117     ISSN:  1388-2457     ISO Abbreviation:  Clin Neurophysiol     Publication Date:  2006 Apr 
Date Detail:
Created Date:  2006-03-20     Completed Date:  2006-06-08     Revised Date:  2008-09-10    
Medline Journal Info:
Nlm Unique ID:  100883319     Medline TA:  Clin Neurophysiol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  838-44     Citation Subset:  IM    
Department of Clinical Neurophysiology, University of Göttingen, Robert-Koch-Street 40, 37075 Göttingen, Germany.
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MeSH Terms
Differential Threshold / physiology
Evoked Potentials, Motor / physiology*
Interneurons / physiology
Motor Cortex / physiology*
Movement / physiology*
Neural Conduction / physiology
Neural Pathways / physiology
Pyramidal Tracts / physiology
Reaction Time / physiology
Reference Values
Transcranial Magnetic Stimulation / instrumentation,  methods*,  standards
Comment In:
Clin Neurophysiol. 2006 Apr;117(4):714-5   [PMID:  16497554 ]

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