coherency.h File Reference

Complex coherency between every channel pair and its two reductions: magnitude (coherence) and imaginary part (imaginary coherence). More...

#include "../connectivity_global.h"
#include "abstractmetric.h"
#include "../connectivitysettings.h"
#include <QSharedPointer>
#include <QMutex>
#include <Eigen/Core>

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Classes
class	CONNECTIVITYLIB::Coherency
	Complex coherency core; produces magnitude-squared and imaginary-part reductions for downstream metrics. More...

Namespaces
namespace	CONNECTIVITYLIB
	Functional connectivity metrics (coherence, PLV, cross-correlation, etc.).

Detailed Description

Complex coherency between every channel pair and its two reductions: magnitude (coherence) and imaginary part (imaginary coherence).

SPDX-License-Identifier: BSD-3-Clause Copyright (c) 2018-2026 MNE-CPP Authors

Author

Daniel Strohmeier danie.nosp@m.l.st.nosp@m.rohme.nosp@m.ier@.nosp@m.gmail.nosp@m..com; Lorenz Esch loren.nosp@m.z.es.nosp@m.ch@tu.nosp@m.-ilm.nosp@m.enau..nosp@m.de; Juan GPC jgarc.nosp@m.iapr.nosp@m.ieto@.nosp@m.mgh..nosp@m.harva.nosp@m.rd.e.nosp@m.du; Gabriel Motta gabri.nosp@m.elbe.nosp@m.nmott.nosp@m.a@gm.nosp@m.ail.c.nosp@m.om; Christoph Dinh chris.nosp@m.toph.nosp@m..dinh.nosp@m.@mne.nosp@m.-cpp..nosp@m.org

Since

0.1.0

Date

April 2018

Coherency is the normalised cross-spectrum,

Coh_{xy}(f) = S_{xy}(f) / sqrt(S_{xx}(f) * S_{yy}(f))

a complex-valued quantity whose magnitude is the classical coherence in [0, 1] and whose argument is the average phase lag between the two signals at frequency f. Splitting it into real and imaginary parts is the basis of the volume-conduction-robust imaginary-coherence estimator of Nolte et al. (NeuroImage, 2004): only non-zero phase lag (i.e. true interaction with finite conduction delay) survives projection onto the imaginary axis, while instantaneous common-reference / volume-conduction mixing contributes only to the real axis and is rejected.

The per-trial workhorse Coherency::compute computes DPSS tapered spectra and accumulates the cross-spectral and auto-spectral sums into the shared ConnectivitySettings::IntermediateSumData. The two public reductions, calculateAbs and calculateImag, then divide by the running auto-spectral norms and average over the frequency window defined on AbstractMetric to produce the scalar edge weights of the returned Network.

Definition in file coherency.h.