Nonlinear analysis of brain magnetoencephalographic activity in Alzheimer disease patients

Non-linear analysis was applied on MEG signals of Alzheimer Disease (AD) patients in order to investigate the underlying complexity of the brain dynamics. A Single channel SQUID was used to record the MEG signals in 9 AD patients and 5 normal individuals. The magnetic activity, for each patient, was recorded from a total of 64 points of the skull (32 points from each temporal lobe). Nonlinear analysis was applied in the abnormal MEG points of the brain. In AD patients some recorded points were found with high amplitudes and low frequencies in magnetic activity. By applying nonlinear analysis in these records low values in the correlation dimension D of the reconstructed phase space were found. SQUID obtained MEG signaling from brains of AD patients showed a lower complexity compared to the brain of normal subjects.