Dear John,
You are almost there. If you install the latest set of SPM8 updates,
you'll find the 'extract' checkbox that will enable you to save the
source time series as SPM dataset when you press the MIP button. A
more convenient way to access this functionality is via SPM batch or
scripts. If you want closer correspondence with fMRI you might want to
use fMRI priors as described in the multimodal faces tutorial.
@meeg methods are described quite in detail in the reference chapter
in the manual. You can also type methods('meeg') in the command line
to get a full list of methods and then type help meeg/<method name> to
get help for each method. However, in this case it's not the object
itself that you need but the inversion results that are stored in
D.inv which is a struct. The fields are briefly described at the end
of 3D source reconstruction chapter.
In general if you want to save something that you can plot in SPM you
can find the code that does the plotting and use it as an example.
Best,
Vladimir
On Wed, Apr 27, 2011 at 6:38 PM, John Sexton <[log in to unmask]> wrote:
> Hello everyone,
>
> I am new to EEG analysis with SPM. I have followed the tutorials in the manual carefully and have managed to get reasonably far on my own, but I am stuck when it comes to digging inside the D meeg object for specific pieces of information.
>
> I have fMRI data and EEG data (collected separately) of subjects viewing faces. So far, I have performed the standard SPM analysis on fMRI data. I have identified the clusters of interest and the corresponding coordinates of the centroids of those clusters in MNI space.
>
> Now this is what I want to do:
>
> 1. Find the point in the EEG data (vertex or sensor) which most closely corresponds to the centroids of the fMRI activation
>
> 2. Extract the time courses for the those points in the EEG data
>
> So far I have entered the coordinates of the fMRI centroids into the "ms or mm" box below the MIP button on the 3D Source Localization window on SPM, then hit the MIP button. This appeared to provide EEG coordinates that were very close to the fMRI coordinates and gave the time (in ms) of peak activity at that coordinate.
>
> For example, if I enter [-39, -46, -23] (obtained from fMRI), the EEG MIP returns [-39, -45, -22] with peak at 195ms.
>
> But now that I have that coordinate (which I assume is the vertex in the EEG data closest to the coordinates I entered), I do not know how to extract the time course of EEG activity associated with it.
>
> This seems like it ought to be easy enough (and there are surely better ways than what I have tried so far), but don't know how to be sure I am getting the correct information.
>
>
> I would greatly appreciate some help on this.
>
> Also, if there any straightforward guide out there to the information contained in the D meeg object, I would love to read it.
>
> Thank you!
>
> John
>
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