JiscMail Logo
Email discussion lists for the UK Education and Research communities

Help for MEGCOMMUNITY Archives


MEGCOMMUNITY Archives

MEGCOMMUNITY Archives


MEGCOMMUNITY@JISCMAIL.AC.UK


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Proportional Font

LISTSERV Archives

LISTSERV Archives

MEGCOMMUNITY Home

MEGCOMMUNITY Home

MEGCOMMUNITY  November 2018

MEGCOMMUNITY November 2018

Options

Subscribe or Unsubscribe

Subscribe or Unsubscribe

Log In

Log In

Get Password

Get Password

Subject:

Comparison of measures of electrophysiological connectivity

From:

Roberto D Pascual-Marqui <[log in to unmask]>

Reply-To:

Roberto D Pascual-Marqui <[log in to unmask]>

Date:

Fri, 2 Nov 2018 01:26:39 +0000

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (22 lines)

Dear Colleagues,
The preprint entitled:
"A comparison of bivariate frequency domain measures of electrophysiological connectivity"
at:
https://doi.org/10.1101/459503
might be of interest to those performing research related to electrophysiological connectivity inference.
The abstract can be found below.
Cordially, Roberto
...
Roberto D. Pascual-Marqui, PhD, PD
The KEY Institute for Brain-Mind Research, University of Zurich
Visiting Professor at Neuropsychiatry, Kansai Medical University, Osaka
[https://www.uzh.ch/keyinst/loreta] [scholar.google.com/citations?user=pascualmarqui]
...

Abstract:
The problem of interest here concerns electrophysiological signals from two cortical sites, acquired as invasive intracranial recordings, or from non-invasive estimates of cortical electric neuronal activity computed from EEG or MEG recordings (see e.g. https://doi.org/10.1101/269753). In the absence of other sources, these measured signals consist of an instantaneous linear mixture of the true, actual, unobserved local signals, due to low spatial resolution and volume conduction. A connectivity measure is unreliable as a true indicator of electrophysiological connectivity if it is not invariant to mixing, or if it reports a significant connection for a mixture of independent signals. In (Vinck et al 2011 Neuroimage 55:1548) it was shown that coherence, imaginary coherence, and phase locking value are not invariant to mixing, while the phase lag index (PLI) and the weighted version (wPLI) are invariant to mixing. Here we show that the lagged coherence (LagCoh) measure (2007, https://arxiv.org/abs/0711.1455), not studied in Vinck et al, is invariant to mixing. Additionally, we present here a new mixture-invariant connectivity statistic: the "standardized imaginary covariance" (sImCov). We also include in the comparisons the directed PLI (dPLI) by Stam et al (2012 Neuroimage 62:1415). Fourier coefficients for "N" trials are generated from a linear unidirectional causal time domain model with electrophysiological delay "k" and regression coefficient "b". 1000 random data sets of "N" trials are simulated, and for each one, and for each connectivity measure, non-parametric randomization tests are performed. The "true positive detection rate" is calculated as the fraction of 1000 cases that have significant connectivity at p<0.05, 0.1, and 0.2. The connectivity methods were compared in terms of detection rates, under non-mixed and mixed conditions, for small and large sample sizes "N", with and without jitter, and for different values of signal to noise. Under mixing, the results show that LagCoh outperforms wPLI, PLI, dPLI, and sImCov. Without mixing, LagCoh and sImCov outperform wPLI, PLI, and dPLI. Finally, it is shown that dPLI is an invalid estimator of flow direction, i.e. it reverses and "goes against the flow" by merely changing the sign of one of the time series, a fact that violates the basic definition of Granger causality.

########################################################################

To unsubscribe from the MEGCOMMUNITY list, click the following link:
https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=MEGCOMMUNITY&A=1

Top of Message | Previous Page | Permalink

JiscMail Tools


RSS Feeds and Sharing


Advanced Options


Archives

November 2018
October 2018
September 2018
August 2018
July 2018
June 2018
May 2018
April 2018
March 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
August 2017
July 2017
June 2017
May 2017
April 2017
March 2017
February 2017
January 2017
December 2016
November 2016
October 2016
September 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
January 2016
December 2015
November 2015
October 2015
September 2015
August 2015
July 2015
June 2015
May 2015
April 2015
March 2015
February 2015
January 2015
December 2014
November 2014
October 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
August 2013
July 2013
June 2013
May 2013
April 2013
March 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
May 2012
April 2012
March 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
September 2010
August 2010
July 2010
May 2010
April 2010
March 2010
February 2010
January 2010


JiscMail is a Jisc service.

View our service policies at https://www.jiscmail.ac.uk/policyandsecurity/ and Jisc's privacy policy at https://www.jisc.ac.uk/website/privacy-notice

Secured by F-Secure Anti-Virus CataList Email List Search Powered by the LISTSERV Email List Manager