Residual ocular artefact subsequent to ocular artefact removal from the electroencephalogram

A method based on the vector representation of electro-oculogram (EOG) and electroencephalogram (EEG) signals has been developed for quantifying in simulation the amount of residual ocular artefact (OA) contamination of EEGs after the application of an EOG-based OA removal (OAR) algorithm. The residual artefact is measured as R², the ratio of residual OA power to the estimated background EEG power. Two types of OA model, the in-plane and the out-of-plane model, were introduced. Values of R² were computed using simulated contaminated EEGs, which were constructed using measured EEGs, contaminated by a variety of eye movements and blinks, and measured EOG signals. In most cases the estimate of R² was approximately 0.03, corresponding to a 17% modification of the EEG voltage. The radial component contributed up to 30% of the residual artefact power. For practical applications, the use of the vertical and horizontal right and the radial EOG components was found to be preferred