[Eeglablist] magnitude squared coherence - trial averaging

Mustapha Mouloua Mustapha.Mouloua at ucf.edu
Tue Jul 8 09:57:18 PDT 2014


Hi EEGLAB Users!  I am having some problems getting my ERP Triggers show up on my  Brainmaster  Discovery”  24-Channel EEG System using an EPrime Language experiment.  They have channels 23 and 24 designated for ERP triggers (pulses and fixation) so  I am only getting pulses and not the trigger numbers (1s and 2s for my 2 experimental conditions) via the stim cable connected to the printer  port.   for my 2 experimental conditions.  Does anyone know how to get these triggers on the brainmaster discovery system or how the EEG can use the pulses to create segmentations for these 2 conditions  I really appreciate any help or input from you.  Cheers!
M. Mouloua, UCF.
From: eeglablist-bounces at sccn.ucsd.edu [mailto:eeglablist-bounces at sccn.ucsd.edu] On Behalf Of Makoto Miyakoshi
Sent: Tuesday, July 08, 2014 12:29 PM
To: Germano Gallicchio
Cc: EEGLAB List
Subject: Re: [Eeglablist] magnitude squared coherence - trial averaging

Dear Germano,

Check out Tim Mullen's SIFT.
http://sccn.ucsd.edu/wiki/SIFT
http://sccn.ucsd.edu/mediawiki/images/d/d2/SIFT_manual_0.1a.pdf

> (3) Do the number of trials per condition influence the computation of the magnitude squared coherence?

I guess so. More trials, more computation, better SNR.

Makoto

On Wed, Jul 2, 2014 at 2:30 AM, Germano Gallicchio <germano.gallicchio at gmail.com<mailto:germano.gallicchio at gmail.com>> wrote:
Dear EEGLAB users,

I am computing the magnitude squared coherence between electrode pairs.

(1) Is there any EEGLAB function to compute this specific kind of coherence measure?

(2) I am currently using the MATLAB function mscohere(), which takes several arguments including the 2 vectors that I want to compare.
Naturally I have several trials per condition and I am not sure which of the following procedures is the correct one:
a. average trials per condition (like I would do for ERPs) and then compute the coherence over these trial-averaged vectors
b. compute coherence for each trial and then average the single-trial coherence, per condition
Could any of you please help me select the right procedure?

(3) Do the number of trials per condition influence the computation of the magnitude squared coherence?

Thanks for your time.

All the best
Germano

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--
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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