Number of highly active columns and EEG frequency. The histogram shows the distribution of the frequency for 213 individuals. The data are from a pilot study described in another paper (Johannisson 2016). In the lower part of the figure, the data have been slightly smoothed and presented as a curved line. This makes it easier to see that there are different frequency groups. The smallest possible number of highly active columns should be found when the limits are set to 0 and 1. This may correspond to the first peak on the left. The other peaks can then be linked to higher limits in consecutive order.