Electrode position optimization for facial EMG measurements for human-computer interface

The aim of this work was to model facial electromyography (fEMG) to find optimal electrode positions for wearable wireless human-computer interface. The measurement system is a head cap developed in our institute and with it we can measure fEMG and electro-oculogram (EOG). The signals could be used to control the computer interface: gaze directions move the cursor and muscle activations correspond to clicking.

A very accurate 3D model of the human head was developed and it was used in the modeling of fEMG. The optimal positions of four electrodes on the forehead measuring the activations of frontalis and corrugator muscles were defined. Calculations were based on reciprocity theorem and lead field concept.

A new accurate model is now in our use for modeling purposes. It has high spatial accuracy and number of inhomogeneities providing a good platform for various simulations. The best measurement sensitivity is achieved by placing the electrodes parallel to the muscle cells. Anyway, better separating capability for frontalis and corrugator activation is achieved by placing the electrodes more orthogonally.

The developed model and the tools utilized are powerful methods to optimize the electrode positions of a wearable gaze and EMG-based user interface system. The modeling results provide direct feedback for developing next generation wearable head cap with optimized electrode locations.