Stimulation Waveform Selection to Suppress Functional Electrical Stimulation Artifact from Surface EMG Signals

Application of facial Neuromuscular Electrical Stimulation (fNMES) in psychophysiological research – practical recommendations based on a systematic review of the literature

“…with a webcam) and to analyse the video with automatic facial action coding, for which several software packages exist (Cheong et al, 2021;Dupré et al, 2020). Finally, additional electrodes might be placed near the fNMES electrodes to record electromyographyhowever, this can be a challenge given the small facial area, and will require cleaning the signal from the important NMES-induced artefacts (Rantanen et al, 2018).…”

“…it was only described as "symmetrical" (e.g. Sapphire, which according to its user manual uses a square wave); 6) in case of polyphasic waveforms (Rantanen et al 2018;Ilves et al, 2020), we provided the frequency of the pulse train, and not of the pulses inside of polyphasic "packages"; 7) if several amplitudes were used, we noted the largest one; 8) separate entries were created if a study included several experiments with different parameters. Once completed, Table 1 was loaded into R, where we computed duty cycle, Irms/cm 2 based on the formulas provided below (section Formulas), unless relevant parameters were missing, which unfortunately was the case for the large majorities (27 of the 34) of studies.…”

“…Another 15 studies had various goals, e.g. they investigated the effects of variations in fNMES parameters on physiology and subjective reports (Ilves et al, 2020;Rantanen et al, 2018), and were thus classified as "Other". Various stimulation sites were targeted, including the frontalis, orbicularis oculi, orbicularis oris, zygomaticus major, depressor anguli oris, and masseter muscles.…”

“…Five studies have investigated the use of fNMES to recover muscular function after Ball's palsy, or other forms of facial paresis (Cui et al, 2021;Makela et al, 2020). The goal of some studies was to further explore the physiological and subjective effects of varying fNMES parameters, such as the waveform (Ilves et al, 2020;Rantanen et al, 2018). Surprisingly, only three studies have used fNMES to modulate mood and/or emotion (Goto et al, 2018;Kapadia et al, 2019;Zariffa et al, 2014), and thus investigate aspects of the facial feedback hypothesis, despite the great potential that this technique has to help investigate aspects central to psychological mechanisms and theories, such as embodied cognition and sensorimotor simulation (Halberstadt et al, 2009;Niedenthal, 2007;Wood et al, 2016).…”

Functional electrical stimulation for facial pacing: Effects of waveforms on movement intensity and ratings of discomfort

“…Simple low-order filters are also an option if the stimulation waveform is properly chosen. For example, wavelets that have highfrequency components can be used [26]. However, the waveform should not have a negative impact on the intensity of the evoked muscle movement compared to more conventional FES waveforms that are simple biphasic square wave pulses with more power at low frequencies.…”