It can be argued that the estimated activity correlates with the underlying neural activity to a certain, limited, extent, but the true underlying neural activity creating the magnetic fields observed in the MEG channels can not be calculated nor visualized 1 to 1. From the same data we can get different visualizations of the brain’s activity using different thresholds. When the threshold is set low, it is more probable that the source estimate visualization highlights also some areas of the brain where no significant change in the true neural activity was actually present. On the other hand, when the threshold is set high, the visualization is more likely to leave out some areas of the brain where there actually was some true significant underlying neural activity. Therefore, an intellectual approach is needed when interpreting the source estimates and using them in a pursuit to arrive at satisfactory conclusions about the underlying neural phenomena.