A convenient method to reduce crosstalk in surface EMG. Cobb Award-winning article, 2001.
OBJECTIVE
Crosstalk in surface EMG can be reduced by the use of spatial filters. We compared a variety of spatial filters to establish the most effective and the least complex method to reduce crosstalk.


METHODS
Six different spatial filters described in the literature were tested in 8 healthy volunteers. Electrode arrays were placed over the anterior tibial and triceps surae muscles. Selective muscle activation was achieved both by supramaximal nerve stimulation and by maximal voluntary contraction. Selectivity of activation was guaranteed by using intramuscular wire electrodes. Crosstalk was quantified by dividing the amount of EMG activity recorded during pure agonist activation (i.e. the muscle directly under the electrode array) by the EMG activity recorded during pure antagonist activation. This was done for both compound muscle action potentials and voluntary muscle activation. The amount of crosstalk recorded with the different spatial filters was compared with that recorded with a standard bipolar lead.


RESULTS
Crosstalk was most reduced by the "double-differential" (DD) filter, yielding an up to 6-fold improvement of EMG selectivity. We then compared signals recorded with this DD filter with those recorded with the less complex "branched electrode". As expected on theoretical grounds, signals from both filter types were identical.


CONCLUSIONS
Crosstalk is best reduced using a "double-differentiating" recording technique, which can be achieved easily using a branched electrode instead of a standard bipolar lead. This technique can be used with all conventional EMG equipment.
Department of Neurology and Clinical Neurophysiology, Leiden University Medical Centre, P.O. Box 9600, 2300 RC Leiden, The Netherlands. vanvugt@knf.azl.nl
J P
JP
van Vugt
J G
JG
van Dijk
D000200:Action Potentials / Q000502:physiology; D000704:Analysis of Variance; D001363:Awards and Prizes; D004566:Electrodes; D004576:Electromyography / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted