Spectral analysis of electroencephalographic recordings of long duration by means of band-pass filters.

A method is proposed for spectral analysis of EEG recordings of long duration, using a set of band-pass filters. The sensitivity of the filters varies continuously over their full range, and the input signal is sampled at every sensitivity level. The full spectrum is presented as an array of numbers where the columns are the frequencies and the rows the sensitivity levels, printed as a percentage of the total possible responses of the filter (percent of activity). The logarithm of the numbers expressing the activity of a filter are used for the calculation of the regression line. Thus, the activity in each frequency is characterized by two parameters, the slope and the ordinate at origin, the slope being the more interesting one.