Real-time estimation of eye gaze by in-ear electrodes

Cognitive control of a hearing aid is the topic for several ongoing studies. The relevance of these studies should be seen in the light of inadequate steering of current hearing aids. While most studies are concerned with auditory attention tracking from the electroencephalogram (EEG), a complimentary approach may be to use visual attention tracking to steer the devices. Visual attention may be characterized by gaze direction, which can be obtained by electrooculography (EOG). EOG may be recorded from electrodes placed in the ear canal, termed EarEOG. To test the comparison of conventional EOG and EarEOG recordings, we conducted two experiments with six subjects. In the first experiment, the subjects were instructed to follow a moving dot on the screen moving in large saccades. In the second experiment, there were five large targets, and within each target, the dot had minor movements. When comparing conventional EOG and EarEOG, correlations of 0.9 and 0.91 with standard deviations of 0.02 were obtained for the two experiments respectively. To assess the feasibility of using EarEOG in real-time, correlation between EarEOG and the timecourse of the dot position was performed. When both signals were filtered with the same real-time applicable filter, correlations of 0.83 and 0.85 with standard deviations of 0.09 and 0.05 were found respectively to the two experiments. In conclusion, this study provides motivational aspects of using EarEOG to estimate eye gaze, as well as it identifies important future challenges in real-time applications to steer external devices such as a hearing aid.