[Eeglablist] ERP statistics and scalp maps of difference waves

[arno]

Dear Dorte,

we fixed this problem recently. It was due to the eeglab2fieldtrip 
function. Just replace it in the Fieldtrip folder.

Best,

Arno

Dörte Spring wrote:
> Dear Stefan and EEGLABler,
>
> thanks so much for the immediate and detailed answer as well as the
> attached mapping code.
>
> Nevertheless, I have detected another problem doing the dipols on raw
> ERPs. As I tried to follow the EEGLAB manual instructions I noticed that
> ICA weights are still necessary, at least to determine the spherical
> model for dipfit. Is that correct?
> However, then I tried to use ICAs for this model specification.
> Unfortunately, it did not work. EEGLAB (5.03; in Matlab 7.0.4.352 (R14)
> Service Pack 2) gave an error (see attached pdf - first page) in the
> second step "Coarse fit". Thus, I dared bravely to run the script for
> ERP dipoles described in the manual. Thereby, I realized that some of
> the needed functions like  "dipfit_erpeeg.m" were missing. I put a
> screen shot of all my plugins/dipfit2.0 and all function files in the
> attached pdf as well (second page). Or could I find this missing file
> maybe elsewhere? At first I thought my eeglab version is not properly
> installed, but nothing changed with a new download and installation.
>
>
> I really appreciate any tips.
>
> Best regards,
>
> Doerte
>
>
>
> Stefan Debener wrote:
>> Dear Doerte,
>>
>> yes, it's all possible with EEGLAB, but requires some scripting 
>> skills. So, the easiest way to do ERP statistics may be to export 
>> your ERP data to SPSS or SAS and define time windows, peak latencies 
>> etc. there. To do this, go to 'File' > 'Export' > 'Export data and 
>> ICA activity to text file', and tick the box 'Export ERP average 
>> instead of single trials'. This is also the easiest way to export 
>> your ERP data into other software such as BESA. Also, check out the 
>> EEGLAB plug-ins (e.g. those from Andreas Widmann), some have been 
>> designed specifically to ease ERP analysis and may come with a nice gui.
>>
>> Regarding the maps, I have attached a little piece of code below. 
>> This code assumes that you have loaded two datasets into EEGLAB 
>> (dataset 1=condition 1, dataset 2=condition 2), that these two 
>> conditions have the same number of frames per epoch (and same epoch 
>> start-stop time) and that you want to plot maps for a mean interval 
>> (t1 to t2) maps. It plots the map for each condition (average across 
>> interval), and the resulting difference map. Look up the help message 
>> of topoplot.m for more options on how to plot nice maps. Also, be 
>> careful with the interpretation of difference maps. We always plot 
>> the difference map together with the single condition maps. 
>> Difference maps can be quite misleading, in particular if the two 
>> maps you are subtracting are different in 'shape', and not only in 
>> 'strength' (amplitude).
>>
>> If you want to do a dipole source analysis of ERPs or ERP difference 
>> maps instead of ICA weights, you can do this with EEGLAB/DIPFIT as 
>> well. Again, it requires some scripting, and is described in detail 
>> in the EEGLAB manual. You may also download Patrick Berg's 
>> DipoleSimulator (www.besa.de), it's a powerful and easy to use free 
>> windows software allowing you to play a bit with how different source 
>> configurations (number, location, orientation) affect the resulting 
>> voltage maps - very instructive.
>>
>> Best,
>> Stefan
>>
>> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>> %start-stop interval (in ms)
>> t1 = 200;
>> t2 = 300;
>>
>> % find corresponding data frames. Code adapted from
>> % Robert Oostenvelds function nearest.m
>> % Copyright (C) 2002, Robert Oostenveld
>> [mindist, t1] = min(abs(ALLEEG(1).times - t1));
>> [mindist, t2] = min(abs(ALLEEG(1).times - t2));
>>
>> % voltage for each electrode, mean across interval and trials
>> data1 = mean(mean(ALLEEG(1).data(:,t1:t2,:),3),2);
>> data2 = mean(mean(ALLEEG(2).data(:,t1:t2,:),3),2);
>>
>> %map scale (in uV)
>> scale = [-4 4];
>>
>> %plot figure
>> figure;
>> subplot(1,3,1);
>> topoplot(data1,EEG.chanlocs, 'maplimits', scale);
>> title('cond 1');
>> subplot(1,3,2);
>> topoplot(data2,EEG.chanlocs, 'maplimits', scale);
>> title('cond 2');
>> subplot(1,3,3);
>> topoplot([data1-data2],EEG.chanlocs, 'maplimits', scale);
>> title('difference: 1-2');
>> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> Dörte Spring wrote:
>>> Dear EEGLABler,
>>>
>>> I'm right now at the point in data analysis where I'd like to do some
>>> statistical analyis as well. My interests lies on ERP and their
>>> components rather than ICA components. Thus, I was wondering whether
>>> there are included some tools for this in EEGLAB that I could use. Im
>>> interested in things like differences in peak amplitude, or peak
>>> latencies for specified ERP components in a certain time window (by
>>> ANOVA for example).
>>>
>>> I also would like to support significant results of this analysis by
>>> scalp maps of the analyzed component's difference wave. Is there a way
>>> in EEGLAB, too, to do that? So far I only have seen the option to topo
>>> plot a component of a single condition, but not the difference 
>>> potential
>>> between two conditions.
>>>
>>> Because all good things come in three, I have another question: Can one
>>> also determine dipoles in EEGLAB withouth ICAs by just using the
>>> difference wave potential in a specific time frame?
>>>
>>> Any suggestions are welcome.
>>>
>>> Best regards,
>>>
>>> Doerte
>>>
>>>   
>>
>>
>>
>>
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> eeglablist mailing list eeglablist at sccn.ucsd.edu
> Eeglablist page: http://sccn.ucsd.edu/eeglab/eeglabmail.html
> To unsubscribe, send an empty email to eeglablist-unsubscribe at sccn.ucsd.edu


-- 

*Arnaud Delorme, Ph.D.*
Swartz Center for Computational Neuroscience, INC, University of San 
Diego California
La Jolla, CA92093-0961, USA

*Tel* :/(+1)-858-458-1927 ext 15/
*Fax* :/(+1)-858-458-1847/
*Web page*: sccn.ucsd.edu/~arno <http://www.sccn.ucsd.edu/%7Earno>
*To think upon*:

    Truth is that which works.

        /Buddha/  

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sccn.ucsd.edu/pipermail/eeglablist/attachments/20061207/d8c9df61/attachment.html>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: eeglab2fieldtrip.m
URL: <http://sccn.ucsd.edu/pipermail/eeglablist/attachments/20061207/d8c9df61/attachment.ksh>