EEG and Brain Connectivity: A Tutorial - Bio-Medical Instruments, Inc.

it requires essentially zero energy to change the phase relationship between
coupled oscillators and by this process rapidly create synchronized clusters
of neural activity. In addition to phase reset without any change in
frequency or amplitude of the EEG spectrum is that it can also be
independent of phase history. That is, phase reset occurs independent of
magnitude and direction of the phase difference that existed before the onset
of the reset pulse (Kazantsev et al, 2004). What is important in the
computation of the first derivative of the time series of phase is the rate of
change of phase over time and not the absolute magnitude of phase.
Figure 11 shows the relationship between phase differences using Cz
as a reference and phase reset as measured by the 1 st derivative of the phase
difference time series.
Fig. 11 – Example of phase difference time series with Cz as the reference (Top) and the
1 st derivative of the phase difference time series (Bottom) or phase reset. Analyses were
produced using the NeuroGuide Lexicor demo from the download at
www.appliedneuroscience.com
Figure 12 shows examples of phase synchrony or phase locking when
the first derivative of the phase difference time series ≈ 0 and phase reset