Document Detail

Extraction of the EPP component from the surface EMG.
MedLine Citation:
PMID:  20016459     Owner:  NLM     Status:  MEDLINE    
A surface electromyogram (EMG), especially when recorded near the neuromuscular junction, is expected to contain the endplate potential (EPP) component which can be extracted with an appropriate signal filter. Two factors are important: the EMG must be recorded in monopolar fashion, and the recording must be done so the low frequency signal corresponding the EPP is not eliminated. This report explains how to extract the EPP component from the EMG of the masseter muscle in a human subject. The surface EMG is recorded from eight sites using traditional disc electrodes aligned along over the muscle, with equal inter-electrode distance from the zygomatic arch to the angle of mandible in response to quick gum clenching. A reference electrode is placed on the tip of the nose. The EPP component is extracted from the raw EMGs by applying a high-cut digital filter (2nd dimension Butterworth filter) with a range of 10-35 Hz. When the filter is set to 10 Hz, the extracted EPP wave deflects either negative or positive depending on the recording site. The difference in the polarity reflects the sink-source relation of the end plate current, with the site showing the most negative deflection corresponding to the neuromuscular junction. In the case of the masseter muscle, the neuromuscular junction is estimated to be located in the inferior portion close to the angle of mandible. The EPP component exhibits an interesting oscillation when the cut-off frequency of the high-cut digital filter is set to 30 Hz. The EPP oscillation indicates that muscle contraction is adjusted in an intermittent manner. Abnormal tremors accompanying various sorts of diseases may be substantially due to this EPP oscillation, which becomes slower and is difficult to cease.
Toshifumi Kumai
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Publication Detail:
Type:  Journal Article; Video-Audio Media     Date:  2009-12-16
Journal Detail:
Title:  Journal of visualized experiments : JoVE     Volume:  -     ISSN:  1940-087X     ISO Abbreviation:  J Vis Exp     Publication Date:  2009  
Date Detail:
Created Date:  2009-12-17     Completed Date:  2010-01-15     Revised Date:  2013-05-31    
Medline Journal Info:
Nlm Unique ID:  101313252     Medline TA:  J Vis Exp     Country:  United States    
Other Details:
Languages:  eng     Pagination:  -     Citation Subset:  IM    
Graduate School of Oral Medicine, Matsumoto Dental University.
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MeSH Terms
Action Potentials / physiology
Electromyography / methods*
Masseter Muscle / innervation*
Motor Endplate / physiology*

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