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Abstract

An electroencephalograph (EEG) signal analyzer allows the examination of the changes in EEG cerebral activity at various sites in response to an event (e.g. a stimulus or task). The analyzer includes one or more signal processing modules which periodically sample the EEG signal from each of the sites, convert the sampled signals to digital sample values, and store those values. Digitized waveforms based on the stored digital sample values and having a length equal to or greater than the period of the lowest frequency of interest are transformed from the time to the frequency domain. For each of a plurality of epochs, a frequency spectrum is produced having frequency content which has a content uniquely due to the digital sample values from that epoch. A weighted means frequency value for each site during each epoch is derived from the corresponding frequency spectrum. Based upon the weighted mean frequency values, output signals are provided to a display and a printer to produce graphical representations of cerebral activity with time at the various sites in response to the event.

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