[Eeglablist] question regarding epochs extracting

[Stephen Politzer-Ahles]

Ida,

To examine event-related potentials you need an event to time-lock the EEG
to; in your case it sounds like what you need is events that indicate the
participant's response (events that are added to the data when the
participant presses a button or does something like that). Without those
events indicating when exactly participants made responses, as far as I
know there is no way to examine event-related potentials based on when they
were performing the task. Some other less timing-precise measures may be
possible, but that's not my area of expertise and I'm not sure how to do
it; I think to be of more help I would need to know what specifically you
are intending to measure.

Best,
Steve Politzer-Ahles

On Mon, Apr 23, 2012 at 1:53 AM, ida miokovic <ida.miokovic at gmail.com>wrote:

> Hello Steve,
>
> thank you very much for your response. Yes, that is my plan - to see what
> is happening during that period of approx 10 secs (it is not in a second
> precise) when participants are performing tasks. It looks similar to this:
>
> .
> .
> S1 (start performing task whenever you want)
> 10 secs
> S11 (stop performing task)
> 30 secs of break
> S1
> 10 secs
> S11
> 30 secs of break
> .
> .
>
> I am not sure how else to extract epochs but with the markers already in
> the data, since I do not have other input of when exactly the subject
> performed the task (I only now they performed it several times within
> marked 10 seconds). Can you please be more specific with your suggestion?
>
> I am beginner in EEGLAB, so this is probably basic question.
>
>
> Thank you once again.
>
> Ida
>
> But my only information of certain period when that period of 10 seconds
>
>
> On Mon, Apr 23, 2012 at 7:56 AM, Stephen Politzer-Ahles <
> politzerahless at gmail.com> wrote:
>
>> Hello Ida,
>>
>> Are you planning to get ERPs locked to participants' responses? If so,
>> you can just extract epochs using the participant responses, rather than S1
>> and S11, as the events.
>>
>> Best,
>> Steve Politzer-Ahles
>>
>> On Sun, Apr 22, 2012 at 4:55 AM, ida miokovic <ida.miokovic at gmail.com>wrote:
>>
>>> Hello everyone,
>>>
>>> I already posted one question when I remembered I have more of them. So,
>>> here it is:
>>>
>>> - I am working with eeg recordings where subjects performed tasks
>>> whenever they wanted during a period within two events (markers). I plan to
>>> do the filtering of the data (lowpass and notch) and to re-reference them
>>> to the average data (ref electrode was Cz). After that, I should do the
>>> epochs extracting, but as I understand EEGLAB does that (within GUI) for
>>> each event in defined interval before and after the event.
>>>
>>> My problem is that I have for example two events - S1 and S11 which
>>> denote start and the end of the experiment. After S1 occurs, 10 seconds (or
>>> similar) after S11 occurs and the subjects are performing tasks within that
>>> period whenever they want. Is there a way for me to say "extract epochs
>>> between events S1 and S11"?
>>>
>>> Thank you once again.
>>>
>>> Ida
>>>
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>>
>>
>>
>> --
>> Stephen Politzer-Ahles
>> University of Kansas
>> Linguistics Department
>> http://www.linguistics.ku.edu/
>>
>
>


-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://www.linguistics.ku.edu/
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