[Eeglablist] epoched or continuous data analysis

[Baris Demiral]

Hi Barkaszi,

After some communications with the EEGLAB people earlier,  I can recommend
you the following:

Epoch all of the data (e.g., all the conditions as S1-ALL.set, S2-ALL.set
etc. for each subject)  with large enough time interval (-300 1500). Then
run ADJUST gross artifact detection/rejection (which will take care of the
very problematic epochs) and then run ADJUST artifact correction (which will
understand the single electrode oriented artifacts, eye blinks, eye
movements and EMG and correct the EEG by reverse mapping the left over ICA
components). EEGLAB has now ADJUST option available.  This is very practical
and quick.

Then you can epoch this set one more time for each condition separately with
a shorter epoch (say -200 900). Then, for each condition, you can run ICA
one more time for the final good ICAs if you are interested in ICA
decompositions more representative of the cognitive elements.

Since it is an oddball task, oddball condition will be much less in number.
But this may still be fine after the artifact corrections. Let me know how
N2-P3 comes put!

Baris

2011/3/21 Barkaszi Irén <barkaszi at cogpsyphy.hu>

>  Dear all,
>
> I ran ICA on my 3-stimulus oddball task with extended infomax algorithm on
> continuous (Neuroscan cnt) and epoched (eeg) data too. I had 800 trials
> (SOA=1000 ms), epoch length was 1000 ms (-200 ms to 800 ms).  The
> components differed in this two analyses (continuous and epoched data, equal
> data length). In the epoched data there are meaningful components which are
> absent in the cnt analysis. There is one blink component in the epoched
> analysis, but in the cnt data several components (more than 10) consist
> blink. Does anyone can explain me my result?
>
> Kind regards,
> Iren
>
>
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-- 
SB Demiral, PhD.
Department of Psychology
7 George Square
The University of Edinburgh
Edinburgh, EH8 9JZ
UK
Phone: +44 (0131) 6503063
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