Online removal of ocular artefacts from the electroencephalogram

A method by which ocular artefacts (OAs) in the electroencephalogram (EEG) may be removed automatically online by electro-oculogram (EOG) subtraction is demonstrated. This is achieved by a combination of recursively calculating the required cross-correlations, a fast matrix inversion method, and the use of a modern microprocessor with a high clock rate. Although recursive calculations are involved, the method itself is essentially non-recursive, which means that distortion of any evoked potentials is minimised. The method may be applied simultaneously to any number of EEG channels.