Facial EMG using BIO2 wide bandwidth Bio-amplifier or EEG8 multi-channel amplifier system

Multiple facial electrode placement in an emotion study

EMG and Startle blink. Facial EMG and eye blink are some of the more demanding applications requiring wide bandwidth and extremely low background interference at very high gain. BioAmplifier is ideally suited to these applications. With facial EMG for emotion studies, it may be required to measure from several sites, in which case the EEG8 amplifier may be more convenient and less costly than multiple BioAmplifier amplifiers, although unlike the multiple BioAmplifier configuration, EEG8 does not allow independent control of each separate amplifier. Otherwise, each EEG8 and BioAmplifier channel are functionally similar.

EL1 (TDE23) 4mm silver / silver chloride re-usable electrodes are positioned across the muscle site and plugged into the white and black differential measurement sockets. A third, separate electrode may be positioned anywhere on the body. This is an ‘isolated ground’ connection, not a ‘reference’ and does not in any way effect the measure between the two active electrodes (other than to reduce noise).

Positions shown in the diagram above are (right and left): A) Medial frontalis, B) Lateral frontalis, C) Levator labii superioris, D) Zygomaticus major.

BioAmplifier and EEG8 have a high pass filter setting of 30Hz, which is ideal for EMG and startle measurement. Gain will normally be set high, possibly to the maximum setting (50uV scale range). Low pass filter may be set to 500Hz to include the full spectrum of EMG energy. If  the EMG trace shows continuously high levels even when the subject is relaxed, the ‘hum’ filter may need to be turned on. This will greatly reduce interference, but will also cut out some of the EMG energy.