[Eeglablist] Fw: question on SICA approach

Mon Feb 18 10:06:11 PST 2008

Hello,
I have data that I wished to import into EEGLAB to run ICA in an attempt
to remove eye movements and artifacts.  All of my subjects are recorded in
90 second blocks with 82 EEG channels recorded at 256 hz.  The majority
have 48 blocks, i.e. 48 X 90 second, thus approximately 72 minutes total
of recording.  However, as stated earlier, they are in separate 90 second
blocks.

As the subjects had brief breaks between these 90 second recordings to
move and/or rest their eyes, the recorder was shut off. Thus the
recordings are NOT continuous for the whole experiment, but only for each
separate 90 second block.

Is it possible to run ICA on this data with the 90 second blocks?  Or is
it not possible as the data is not continuous?

Could I concatenate the data, all 48 90 second blocks, into one large
matrix, and import it into EEGLAB to run ICA?  Or would this not work as
it really was not continuous data in the first place?

There are 10 different conditions and only two require responses.  This is
all done with markers for the reaction times, conditions, false alarms,
etc.  Is there any protocol to deal with markers in EEGLAB?

Thanks,
Ed

> Frederica -
>   You've misinterpreted -- ICA learns a (channels,channels) unmixing
> matrix,
> so the number of data frames (time points) needed to separate as many
> components increases as the square of the number of channels. The faq is a
> bit out of date -- in our work with 72-256 channel data in the lab, we
> have
> found that as the channel density becomes high, good ICA solutions
> typically
> require a considerable multiple of the channel number squared (up to 30 or
> more for 256-channel data).
>
> For 148-channel data I would like to collect 30*128^2 ~ 650k (~40 min of
> data at 256 Hz) ... though it could well be that smaller data sets could
> also give useful solutions. I will update the faq to better reflect this,
> and will try to do a numerical study to get a more detailed heuristic
> understanding.
>
> Scott Makeig
>
> On Feb 16, 2008 2:36 AM, Federica Di Grazia <federicadigrazia at hotmail.com>
> wrote:
>
>>
>> ----- Original Message ----- *From:* Federica Di
>> Grazia<federicadigrazia at hotmail.com>
>> *To:* eeglablist at sccn.ucsd.edu
>> *Sent:* Tuesday, January 29, 2008 10:13 PM
>> *Subject:* question on SICA approach
>>
>> I saw the faq on Independent Component Analysis but I couldn't
>> understand
>> how many samples(in time) I need to analyze 148 channels with SICA
>> approach?
>>
>> I saw that it's necessary a number of samples(in time) equal to the
>> square
>> of the channels, but for SICA  the sample are represented by the 148
>> channels, so I need the square root of 148 as samples(in time)?
>>
>>
>>
>> Best Regards,
>>
>> ____________________________________________________________________
>>
>> Federica Di Grazia
>> Ph. D. Student in Electronics, Automation and Complex Systems
>> Engineering
>> Dipartimento di Ingegneria Elettrica Elettronica e dei Sistemi
>> Università degli Studi di Catania
>> v.le A.Doria 6 - 95125 Catania, Italy
>> Tel. +39-095-7382342
>> Fax +39-095-330793
>> e-mail: fdigra at diees.ing.unict.it
>>            federicadigrazia at hotmail.com
>> ____________________________________________________________________
>>
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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 92093-0961, http://sccn.ucsd.edu/~scott
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---------------------------------------------------
Edward Justin Modestino, M.Phil.
Ph.D. Candidate in Complex Systems and Brain Sciences
Cognitive Neurodynamics Laboratory
Center for Complex Systems and Brain Sciences
Florida Atlantic University
(561) 297-2238
Fax: (561) 297-3634
modestino at ccs.fau.edu
http://www.ccs.fau.edu/~modestino/
Lab: http://www.ccs.fau.edu/~bressler/CNL_CCSBS/CNL_CCSBS_FAU.html
---------------------------------------------------