Single motor unit analysis from spatially filtered surface electromyogram signals. Part I: Spatial selectivity

2003 ◽  
Vol 41 (3) ◽  
pp. 330-337 ◽  
Author(s):  
D. Farina ◽  
E. Schulte ◽  
R. Merletti ◽  
G. Rau ◽  
C. Disselhorst-Klug
Keyword(s):  
Motor Unit ◽  
Surface Electromyogram ◽  
Single Motor Unit ◽  
Spatial Selectivity ◽  
Single Motor ◽  
Unit Analysis

Optimal placement of bipolar surface EMG electrodes in the face based on single motor unit analysis

2010 ◽  
Vol 47 (2) ◽  
pp. 299-314 ◽  
Author(s):  
Bernd G. Lapatki ◽  
Robert Oostenveld ◽  
Johannes P. Van Dijk ◽  
Irmtrud E. Jonas ◽  
Machiel J. Zwarts ◽  
...  
Keyword(s):  
Motor Unit ◽  
Surface Emg ◽  
Optimal Placement ◽  
Single Motor Unit ◽  
Single Motor ◽  
The Face ◽  
Emg Electrodes ◽  
Unit Analysis

Rectification is required to extract oscillatory envelope modulation from surface electromyographic signals

2014 ◽  
Vol 112 (7) ◽  
pp. 1685-1691 ◽  
Author(s):  
Christopher J. Dakin ◽  
Brian H. Dalton ◽  
Billy L. Luu ◽  
Jean-Sébastien Blouin
Keyword(s):  
Motor Unit ◽  
Stimulus Frequency ◽  
Motor Units ◽  
Surface Emg ◽  
Medial Gastrocnemius ◽  
Single Motor Unit ◽  
Single Motor ◽  
Single Motor Units ◽  
Emg Signal ◽  
Envelope Modulation

Rectification of surface electromyographic (EMG) recordings prior to their correlation with other signals is a widely used form of preprocessing. Recently this practice has come into question, elevating the subject of EMG rectification to a topic of much debate. Proponents for rectifying suggest it accentuates the EMG spike timing information, whereas opponents indicate it is unnecessary and its nonlinear distortion of data is potentially destructive. Here we examine the necessity of rectification on the extraction of muscle responses, but for the first time using a known oscillatory input to the muscle in the form of electrical vestibular stimulation. Participants were exposed to sinusoidal vestibular stimuli while surface and intramuscular EMG were recorded from the left medial gastrocnemius. We compared the unrectified and rectified surface EMG to single motor units to determine which method best identified stimulus-EMG coherence and phase at the single-motor unit level. Surface EMG modulation at the stimulus frequency was obvious in the unrectified surface EMG. However, this modulation was not identified by the fast Fourier transform, and therefore stimulus coherence with the unrectified EMG signal failed to capture this covariance. Both the rectified surface EMG and single motor units displayed significant coherence over the entire stimulus bandwidth (1–20 Hz). Furthermore, the stimulus-phase relationship for the rectified EMG and motor units shared a moderate correlation ( r = 0.56). These data indicate that rectification of surface EMG is a necessary step to extract EMG envelope modulation due to motor unit entrainment to a known stimulus.

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