[Eeglablist] (ask) about averaging and ICA

Tarik S Bel-Bahar tarikbelbahar at gmail.com
Sun Dec 26 17:45:01 PST 2010


Greetings Bagas,

1. Yes, there are multiple papers that refer to this issue. I would suggest
you start
with the HANDBOOKS by Tom Handy or Steve Luck, and these will answer your
basic questions about the relations
between trial counts, averaged ERPs, and the resultant signal-to-noise
ratios.
You can find these books by doing a Google search, and you can order them
from Amazon or another bookseller.
Here's the link for the Handy handbook:
http://mitpress.mit.edu/catalog/item/default.asp?tid=10253&ttype=2

2. Your second question is not clear. It's not clear what you mean by "many
trials" or only "single-trials" in one epoch.
For information about best practice using EEGLAB and ICA, please read
through the EEGLAB tutorial online.
A general rule of thumb is that more single trials are better than fewer
single trials, for an accurate ICA decomposition of the data.

3. Again, you should read and learn basic information about ERP techniques
from handbooks mentioned in Point 1 above,
or in articles that use ERPs (please search on Google Scholar for examples
that relate to your research questions).
It also not clear what you mean by using "only one technique".
You can generate average ERPs without using ICA, and you can also generate
ERPs after using ICA.
Please be aware that the emphasis in EEGLAB is on single-trial analysis,
although it can certainly be used for single subject average ERPs.

4. In the future please try to be more specific about what you are trying to
do, what kind of ERPs you are trying to generate.
Also it seems that you are unaware of the the many potential uses of ICA
(for artifact detection, for detection of independent modulators, etc..)
Please read through the articles describing EEGLAB (which you can find at
the EEGLAB site, or via Google Scholar).
Please also read through and do the EEGLAB tutorial, which will answer some
of your questions.
Then feel free to send some more questions after that.

Good luck Bagas!





On Thu, Dec 23, 2010 at 1:09 AM, Bagas Isadewa <izadewa at yahoo.com> wrote:

>  hello,
>
> i have several questions,
>
> 1. if I wanted to average EEG data to yields good ERP, how many minimum
> trials do I needed ? is there any paper or journals that explained about it
> ?
> 2. then, if I wanted to run ICA to extract ERP, do I need many trials or
> only single-trials in one epoch will be enough ??
> 3. is it necessary to run ICA first then do averaging or it is enough to
> use only one technique for extracting ERP ?
>
> if you don't mind please give me an explanation
> thank you very much
>
>
> regards,
> bagas isadewa
>
>
>
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