Synergetic analysis of spatio-temporal EEG patterns: Alzheimer's disease

A spatio-temporal analysis has been employed on EEG signals recorded in gro ups of patients with Alzheimer's disease (AD). The so-called Karhunen-Loeve analysis method was applied to four groups of subjects: 12 patients who we re diagnosed as having severe AD, 8 mild AD patients, 10 vascular dementia patients, and 10 normal aged controls, to obtain the spatio-temporal eigenp atterns. The local difference of the global EEG pattern in mild AD patients from that of normal controls was expanded to the frontal regions in the ca se of severe AD. The analysis showed significant bilateral temporal functio ning differences and interhemispheric connection difficulty, along with rem arkable intra-hemispheric correlation in severe AD patients. Compared to th e normal controls, severe AD patients' brains exhibit only weak local conne ctions and correlations, resulting into limited harmonious inter-hemispheri c information processing. The results from the spatio-temporal EEG study of AD patients can be considered to be due to a change in the relative activi ty of the brain corresponding to the pathologic variation in AD, and the re sults are in accordance with reported clinical studies.