[Eeglablist] Source analysis trade-offs: ICA + ECD versus distributed methods

[Fine, Justin Michael]

Dear list:

I have a question that the literature does not really seem to answer regarding source analysis: why would someone prefer findings a priori known sources in EEG with a given source methods? Specifically, I am asking about the benefits and obvious trade-offs if (1) ICA + ECD ,(2) distributed (and sparse or group hierarchical methods) source methods (e.g., MSP in SPM) or (3) a Bayesian ECD approach which does not rely on fitting separate IC components but relies on specifying a prior source locations?

Quick background, I have T1s and recorded electrode positions (64 channel acticap) for all participants.  The main goal here is extracting time-frequency and evoked (ERP) from an rIFG, pre-SMA/ACC/MCC, and left M1 source.The study was a standard stop signal task, of which the literature tends to prefer the method (1) of ICA + ECD. But I gather that might have something to do with researchers typically (1) not having electrode locations and (2) T1s?      

Any thoughts and feedback would be greatly appreciated. 

Thanks!
Justin Fine
Post-doctoral researcher
Indiana University
-----Original Message-----
From: eeglablist <eeglablist-bounces at sccn.ucsd.edu> On Behalf Of Scott Makeig
Sent: Friday, January 8, 2021 2:32 PM
To: JULIANA CORLIER <corlier at g.ucla.edu>; Johanna Wagner <joa.wagn at gmail.com>
Cc: eeglablist at sccn.ucsd.edu
Subject: [External] Re: [Eeglablist] Analysis of TMS-induced harmonics in the EEG

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Juliana -

These will also soon be a new toolbox, the 'Independent Modulator Analysis Toolbox' (IMAT), that can separate harmonic from non-harmonic activity. If you might like to test its use, write Johanna Wagner <joa.wagn at gmail.com>.

Scott Makeig

On Thu, Jan 7, 2021 at 3:20 PM JULIANA CORLIER <corlier at g.ucla.edu> wrote:

> Dear list,
>
> I would like to get some expert advice on how to assess/quantify the 
> presence of harmonics in the EEG.
> Notably, our lab is using EEG recordings during repetitive 
> transcranial magnetic stimulation (TMS) and we would like to assess 
> whether the stimulation at a certain frequency elicits an entrainment 
> at the stimulation frequency but also at other frequencies.
>
> My first approach was to check for ‘ratios of frequencies’ that show 
> activation in the time-frequecy domain post stimulation, but that 
> turned out to be a more tricky than I have aniticipated.
> I was wondering if there is a proper approach to harmonics analysis?
> One would think that engineers and signal processing experts outside 
> of neurosciences deal all the time with that.
>
> Any advice is much appreciated!
>
> Thank you!
>
> Juliana Corlier
>
>
>
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--
Scott Makeig, Research Scientist and Director, Swartz Center for Computational Neuroscience, Institute for Neural Computation, University of California San Diego, La Jolla CA 92093-0559, http://sccn.ucsd.edu/~scott _______________________________________________
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