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

Fig. 38 – Illustrates the constant phase differences as a function of time when two
different frequencies are phase locked. Cross-frequency phase locking and crossfrequency
phase shift are measured by the 2 nd derivative of instantaneous cross-frequency
phase differences which = 0 when there is phase locking and is > 0 when there is a crossfrequency
phase shift.
Figure 39 illustrates the measures that are computed in order to
quantify cross-frequency phase lock duration and cross-frequency phase
shift duration in milliseconds. The average magnitude of phase locking is
directly related to the average magnitude of the 2 nd derivative during the
phase lock periods.