Application to biomedical signals - Practical Biomedical Signal Analysis Using MATLAB - page 119

tance, which is a rather trivial observation. Partial coherences show only direct con-
nections between channels and the information provided by them is much more se-
lective. The computation of ordinary, partial, and multiple coherences can be easily
achieved in the framework of MVAR.
FIGURE 4.8: Coherences: ordinary—above diagonal, partial—below diagonal
and multiple—on the diagonal for stage 2 of Sleep EEG. From [Kaminski et al.,
1997].
The important problem in brain research is the estimation of functional connectiv-
ity and the determination of the direction of the propagation of EEG signals. It was
approached by the estimation of phase difference between channels, but as was ex-
plained in Sect.3.5, the method gives ambiguous and sometimes misleading results.