Abstract
The lag synchronisation of two different chaotic oscillators is a phenomenon that occurs when the signal from a lower frequency system is delayed with respect to a higher frequency system. The interaction among the multiple brain oscillators might produce lag synchronisation.
In addition, phase differences between EEG channels might also reflect this "time delay" phenomenon. It has been suggested that the lag-synchronisation of chaotic oscillators depends on the direction of the delay differences between characteristic frequencies.
The purpose of this study was to determine whether the direction of the phase difference between two electroencephalography (EEG) channels depends on the source of the characteristic frequency. The dependence of the phase shift on the mean frequency between two channels were examined in a group of 17,722 healthy truck drivers.
The mean phase difference between two EEG channels was estimated using the Hilbert transform and compared with the difference in the characteristic frequency. The number of EEG segments with a phase delay from the electrode with a lower frequency to the electrode with a higher frequency was significantly higher than that moving in the opposite direction.
The most significant direction of the phase delay was occipito-frontal. These results support the hypothesis that lag synchronisation occurs in the human brain as a result of phase differences that lead to "time delays" in the transfer of information from one part of the brain to another.
However, this mechanism does not explain the dependence of phase differences on the frequencies between the electrodes. This work provides an alternative explanation for the phase shift between oscillations in different parts of the brain by the theory of nonlinear dynamical systems.