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

Fig. 6 - Illustration of a cortico-cortical connection model. Top is the organization of
intra-cortical connections according to Schulz and Braitenberg (2002). A = gray matter
intra-cortical connections, B = ‘U’ shaped white matter connections and C = long
distance white matter connections. Bottom is an exemplar contour map of source
correlations in which the horizontal bands of increasing and decreasing source
correlations correspond to the different cortico-cortical connection systems as described
in the top of the figure. From Thatcher et al, 2006.
6- What is Coherence?
Coherence is a measure of the amount of phase stability or phase jitter
between two different time series. Coherence combines something
analogous to the “Pearson product-moment correlation” to the phase angles
between two signals. When the phase difference between two signals is
constant than coherence = 1, when the phase difference between signals is
random then coherence = 0. It is possible for there to be a constant phase
angle difference at two different frequencies. In the later case the
terminology is cross-frequency coherence or bi-spectral coherence or n:m
phase synchrony (Schack et al, 2002; 2005). If the measures are within the
same frequency band, then the terminology is simply “coherence” which
assumes auto-frequency coherence. Coherence is mathematically analogous