AN INVESTIGATION OF THE IN-PHASE INTERACTIONS OF EEG SIGNALS

A new method of measuring the interactions between different cortical areas of the brain is presented in this thesis. It is based on the hypothesis that gross EEG signals are produced through summation of synchronized activities of a small fraction of the cerebral neuronal population. When two areas of the brain are in active functional communication, some meaningful relationship should exist between the EEG signals. The in-phase interaction parameter between any two brain areas is defined as the number of times the peaks or troughs of the corresponding EEG signals occur in-phase within a certain time interval. A real time software system was developed to detect the amplitudes and intervals of the eight EEG signals simultaneously. The zero crossing technique was used for on-line detection. The ability of the new method to detect and localize the changes in the interactions between the different cortical areas in the normal range was tested. Two different stimuli were applied. The first was fist clenching. The second was the vision stimulus. In addition to evaluating changes in the normal range, it was also possible to measure the degree of neurodisconnection in abnormal EEG\u27s. In conclusion, the study reported in this dissertation would show that the in-phase interaction method of analysis is a powerful and sensitive means of detecting, localizing, and mapping the neural interactions beween different cortical areas as they are reflected in their corresponding EEG activity. This would allow investigation of human cortical physiology at a higher level than previously thought possible