[Eeglablist] pop_rmbase timelocking

[Arnaud Delorme]

Dear Katherine,

Here is a possible workaround.
First extract large data epochs around the fixation cross and remove the baseline.
Epoched dataset can be re-epoched if necessary.
So second, extract data epochs around the movement onset and do not remove any baseline.
This should do the trick,

Arno

On 4 Oct 2012, at 12:49, Stephen Politzer-Ahles wrote:

> Hi Katherine,
> 
> The times in pop_rmbase are relative to the time-locking event, rather than the start of the epoch. 
> 
> As for your second question, I don't know a way to do this in the EEGLAB GUI or with built-in functions (although if someone else knows, that would be great), but it's certainly possible to do it with some code. You would just need some code that iterates through epochs and, for each epoch, calculates the mean of some window before the fixation cross (you can find the latency of the fixation cross using EEG.epoch(i).eventtype and EEG.epoch(i).eventlatency), and subtracts that value from the whole epoch.
> 
> Best,
> Steve
> 
> On Thu, Oct 4, 2012 at 2:55 AM, Katherine Naish <K.R.Naish at pgr.reading.ac.uk> wrote:
> Hi,
> 
> When using pop_rmbase, are min_ms and max_ms relative to the start of the epoch, or to the timelocking event that the epoch was based around? So, the number that are entered as timerange if using code- or the numbers in the 'baseline latency range' in the pop-up window- if I enter [-500 0] is that taking 500ms before the start of the epoch?
> 
>  
> Is there a way to specify a baseline period that is locked round an event which isn't always in the same place in the epoch? For example, I am interested in what is happening around one event (movement onset), but I would like the baseline to be based around the participants viewing a fixation cross. But the period between the fixation cross and movement onset is variable. Is there a way to specify time points based around the fixation cross for the baseline, or does the fact that the time period varies present a problem?
> 
>  
> Thanks,
> 
> katherine
> 
>  
> ~~~~~~~~~~~~~~~~~~~~~~~~
> Katherine Naish
> PhD student
> School of Psychology
> University of Reading & Goldsmiths, University of London
> http://www.neurobiography.info/handlab.php?page=people
>  
> 
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> -- 
> Stephen Politzer-Ahles
> University of Kansas
> Linguistics Department
> http://people.ku.edu/~sjpa/
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