Self-organizing map in recognition of topographic patterns of EEG spectra

The self-organizing map, a neural network algorithm, was applied to the recognition of topographic patterns in clinical 22-channel EEG. Inputs to the map were extracted from short-time power spectra of all channels. Each location on a self-organized map entails a model for a cluster of similar input patterns; the best-matching model determines the location of a sample on the map. Thus, an instantaneous topographic EEG pattern corresponds to the location of the sample, and changes with time correspond to the trajectories of consecutive samples. EEG segments of "alpha", "alpha attenuation", "theta of drowsiness", "eye movements", "EMG artifact", and "electrode artifacts" were selected and labeled by visual inspection of the original records. The map locations of the labeled segments were different; the map thus distinguished between them. The locations of individual EEG\´s on the "alpha-area" of the map were also different. The clustering and easily understandable visualization of topographic EEG patterns are obtainable on a self-organized map in real time.