Segmentation of the spontaneous EEG in dementia of the Alzheimer type.

Studies on EEG data in dementia of the Alzheimer type have mainly investigated parameters in the frequency domain. However, the EEG also reflects the momentary functional state of the brain. The EEG can be partitioned into segments of spatially stationary map landscapes as characterized by the locations of potential maxima and minima, to study the time domain of the EEG. We calculated the segment structure of 19-channel EEG recordings (1-30 Hz) from 10 patients with dementia of the Alzheimer type and 10 sex-matched geriatric controls. The EEG maps corresponding to global field power peaks were used for analysis. The locations of the potential maximum and minimum of the maps were determined over the course of 20 s and used for segmentation. The segments of EEG activity were significantly fewer (p < 0.05) and the segments lasted longer (p < 0.05) in patients compared to controls. This effect could be observed over the whole period of recording and thus was not caused by only a few long segments. The data may be linked to morphological and biochemical findings of neuronal loss and loss of synapses in dementia of the Alzheimer type.