Have you ever asked yourself why the BESA artifact correction is so incredibly good? Compared to other approaches, there is very little – if any – distortion in the signal of interest after suppressing the likes of eye movements, blinks, and EKG artifacts. One of the reasons is described in the – slightly dusty, but still sparkling under the patina – paper by Patrick Berg and Michael Scherg published in 1994, which they titled “A multiple source approach to the correction of eye artifacts” (Berg P and Scherg M, Electroencephalography and clinical Neurophysiology 90, 229-241, 1994).
The authors put across the idea of overlapping a model of brain activity with the spatial vectors describing the artifact, thus largely enabling protecting brain signal of interest from distortion by the artifact reduction process – which is particularly important when brain area of interest and artifact have a spatial correlation with each other. This idea was further refined later on (cf. Ille N et al., Journal of Clinical Neurophysiology 19: 113-124, 2002), and of course also other artifact reduction methods like ICA have gained popularity and have also found their way into the BESA software. But the principle is still very much alive and shows the forward-thinking power of the BESA engineers, which is still a large component in designing solutions and features today.
By the way, Michael and Patrick, who have provided many other innovative concepts over the years, still collaborate to this day on new ideas for improving or automating EEG and MEG signal analysis.