[Eeglablist] How to do the MMN substraction?

[Stephen Politzer-Ahles]

Hi Pengmin,

The ERP data for a dataset is stored in the EEG.data variable once you've
loaded a dataset. So if you want to derive the subtraction wave for a given
subject, you can first open the 'standard stimulus' file for that subject,
then get the data using something like

standard = EEG.data;

then open the 'oddball stimulus' for that subject, do

EEG.data = EEG.data - standard;

then save the set with a new name; you could do that for each subject.

Alternatively, if you just want to quickly plot the grand average
difference wave, you can do this by opening all the subjects' datasets at
once and then use "Plot > Sum/Compare ERPs" from the menu in the EEGLAB
interface.

Best,
Steve Politzer-Ahles

On Tue, Mar 20, 2012 at 3:21 PM, PengMin Qin <qin.pengmin at gmail.com> wrote:

> Hello,
>
> I am fresh user of EEGLab. I have one mismatch negativity dataset. I need
> to substract ERP of the 'standard stimuli' from ERP of the 'oddball
> stimuli' to the get the mismatch negativity waveform. How to do this
> substraction by using of EEGLAB?
>
> There is another question about ITC. I generated the "####.datitc" file
> for each participant by using "study -> precompute channel measures".
> Beside the EEG data, we also acquire behavioral data. I plan to draw the
> ITC results to do the correlation between ITC data and behavioral data. As
> I understand, the ITC should be a value from 0 to 1. But when I open the
> "####.datitc" file, I did not find the value from o to 1, but a value like
> "-0.1653+0.0860i". How to use the ITC data?  How to do the correlation
> between ITC and behavioral data?
>
> Thank you very much!!
>
> Best,
> Pengmin
>
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-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://www.linguistics.ku.edu/
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