[Eeglablist] Subtract individual subject mean spectrum...what does that mean?

[krishnaj gourab]

Hello,

I am researcher is Marquette University in Milwaukee, WI and I am using
Eeglab to process data. I am  looking at the differences in frequency power
when subjects carry out a movement volitionally (active ) versus when the
same movement is performed passively.

I have created a .study file which has 9 datasets (1 for each subject) for 2
conditions (active versus passive). I am plotting topographic maps for the
power for the 15 Hz frequency for each subject and condition- yielding 9
maps for the active condition, and 9 for the passive condition.  I am
interested in knowing if there is a statistically significant difference in
the topography of these maps.

In the Study tab, I used the "Precompute channel measure" to precompute the
power spectrum for this .study file. Then I used "Plot channel measures" to
plot the topographic maps for the frequency.  In "Plot channel measures",
there is a button "Params" between "Plot Spectra". When I press "Params", I
get the option "Subtract individual subject mean spectrum".

The topography of my maps change when I select this option versus when I do
to select this option.

I wanted to know, what exactly does the option "Subtract individual subject
mean spectrum" do?

I looked in the manual but I don't think it is mentioned there.

Could you please explain me more about this?

I will really appreciate any input/suggestions.



Thank you.



Krishnaj
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