[Eeglablist] ICA for ERP analysis

[Makoto Miyakoshi]

Dear David,

I found your decomposition results are very poor, and I'm sorry for saying
this.
Would you mind trying this?

1. Filter the data with bandpass 1-50 Hz using eegfiltnew() from GUI (use
the latest EEGLAB)
2. Reject bad epoch/time window. If you don't feel like spending too long
time on this, use my plugin trimOutlier
http://sccn.ucsd.edu/wiki/Plugin_list_process
3. Run ICA.

Note that
1. 15Hz low-pass could have made the rank deficient
2. short baseline subtraction may have compromised ICA
3. z-normalized, for each channel? That is bad for ICA. ICA examines
across-channel amplitudes for every single datapoint.

And how many datapoints do you have for ICA? Make sure it is more than
(channel^2)*20.

Makoto


2014-04-09 8:01 GMT-07:00 David Kaufman <david.kaufman at gmx.de>:

> Dear EEGLAB list,
>
> I'm trying to extract independent components for my ERP single trial
> analysis. I'm receiving these components by filtering my raw data with a
> low pass filter of 15 Hz and extracting trials with stimulus onset. The
> base line of the trials is removed by using a pre-trial of 300 ms.
> Non-trials are cut out before the pre-trial. All trials, i.e. non-trials
> and trials are z normalized and concatenated and fed to the amica [0]
> function.
>
> The resulting components look like this:
> https://dl.dropboxusercontent.com/u/2635172/AMICA.png
>
> As you can see many components are localized around one electrode
> (3,4,5,6,8,9,10,11,12, ...). Almost all of my subjects have these focused
> components. Is this normal or do I have a error in my setup? Any help is
> greatly appreciated.
>
> [0] http://sccn.ucsd.edu/~jason/amica_web.html
>
> Regards,
> David
>
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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