[Eeglablist] baseline for response-locked ERPs

[Tarik S Bel-Bahar]

You can baseline in a rainbow of ways, even from erp or eeg info from other
kinds of trials, from rest periods, etc.
Imho, you should examine for yourself each of your suggestions, with your
data, and examine the differences.

Further, you should emulate data analysis choices from the published
literature which determined your tasks and questions, and to whom you will
related your findings.

In my work with finger movement, ive looked at the response erp by locking
to stimulus, and also by locking to response. I guess it most depends on
your theory of the best baseline, cognitively speaking.

Last, also check the baseline parametrization in the latest crop of ern
articles. cheers!
On Feb 2, 2012 11:26 AM, "Elise Radtke" <eliseradtke at yahoo.de> wrote:

> Dear all,
>
> I was wondering, whether anybody has experience in / ideas about baseline
> corrections concerning response-locked ERPs. We are primarily interested
> in processes happening directly before participants come to a decison, i.e.
> press a key.
> Our experimental setup was the following: After a fixation cross, a prime
> word (positve/negative) was presented for 300 ms, followed by a target,
> where subjects had to make a binary decision and indicate it by keypress. Participants
> responded without having any time restrictions. The averaged Response
> Times varied from 1200-3000 ms.
>
> Having these varying RTs, 3 possibilities come to my mind, how to set the
> baselines, when epoching the data:
>
> 1) Using the 500ms before target presentation or prime as baseline.
> 2) Determining a baseline relative to response e.g. 1500 ms to 1000 ms
> before button press. This would raise the problem, that the baseline varies
> between trials, it can be either post- or pre-target, or even on the target.
> 3) Using the average voltage of the whole epoch and subtracting it from
> the epoch data, as proposed by Steven Luck in his book (2005).
> It would be nice if you have some opinion or an idea how to deal with the
> problem.
>
> Best
>
> Elise
>
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