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

Fig. 13- Diagram of phase reset metrics. Phase shift (PS) onset was defined at the time point when a
significant 1 st derivative occurred (≥ 5 0 /centisecond), phase shift duration (SD) was defined as the time
from onset to offset of the phase shift and the phase synchrony interval (SI) was defined as the interval of
time between the onset of a phase shift and the onset of a subsequent phase shift. Phase reset (PR) is
composed of two events: 1- a phase shift and 2- a period of synchrony following the phase shift where the
1 st derivative ≈ 0 or PR = SD + SI. (from Thatcher et al, 2008a; 2008b)
17- How large should coherence be before Phase Difference can be
regarded as stable?
As mentioned previously, the confidence internal for the estimation of
the average phase angle between two time series is related to the magnitude
of coherence. When coherence is near unity then the oscillators are
synchronized and phase and frequency locked. This means that when
coherence is too low, e.g., < 0.2, then the estimate of the average phase
angle may not be stable and phase relationships could be non-linear and not
synchronized or phase locked. An example of a 30 degree phase angle
using the NeuroGuide signal generation program is shown in figure 13: