[Eeglablist] Baseline

[Tarik S Bel-Bahar]

Hello Lucia, here are some notes below that may help. Cheers.




1. If you haven't had a chance to yet, consider looking at the baselining
tutorials and "defaults" for eeglab, fieldtrip, and other programs. You can
also see what the usual baselines are in their tutorial data. Of course,
just surveying 20 or 30 articles via Google Scholar from top journals in
EEG using a protocol similar to yours would give you a good sense of the
current norm.
2. Baselines usually range from -100 to -1000 ms before the period. It
depends on how clean and stable they are. Some groups ask for a period of
stillness or fixation on a cross in the second preceding the stimulus onset
per trial, so as to maximize having a good baseline.
3. If you're averaging trials, you can look at your grand averages with and
without baseline.It won't hurt to see for yourself what the difference is.
You can also practice with shorter or longer baselines to see the effect on
your grand averages.
4. Baselining is the norm if you are looking at post-stimulus event-related
activity, including classic ERP's. Steve Luck's book on Intro to ERP
technique (and slides related to the book) refer to baselining and it's
effects, as well as other handbooks oriented towards ERP analyses.
5. There are various ways to baseline. See some recent articles via Google
scholar about how to treat ERPs, single-trials, and issues in baselining
(e.g., a recent article from  Delorme and colleagues that talked about
taking the average baseline across the whole trial.
6. If you are doing pre-stimulus period analyses there are different
considerations. Just google eeglablist or google-scholar for these articles.
7. Overall the baseline should be a relatively "neutral" prestimulus period
that serves as an adequate and "valid" period against which to compare
post-stimulus activity. Most classic ERPs and components "pop out" best in
grand-averages when they are baselined.
8. You may also benefit from checking out the EEG Publication standards
from Keil et al (2014) published in Psychophysiology
9. Last, there may be no true baseline or any period in brain activity that
serves as a true neutral baseline. For example, resting with eyes closed
but awake is never "just resting". In short there is always brain-mind
activity going on. In traditional baseline period per trial in classic ERP
paradigms, it's usually the case that the baseline period contains some
mental activity related to preparing/expecting the next
stimulus/trial/response.








On Wed, Feb 3, 2016 at 4:17 AM, Lucia Brini <brinilucia at gmail.com> wrote:

> Good morning,
>
> I’d like to ask you some questions about the baseline: how can I decide if
> remove it or not? Are there precise criteria? Because I’m doing a study on
> the five-box task and I can’t appreciate if I have to remove it or not.
>
> Thank for your attention.
>
>
>
> Lucia
>
>
>
> Inviato da Posta <http://go.microsoft.com/fwlink/?LinkId=550986> per
> Windows 10
>
>
>
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