MEM Source imaging

1

Dear Brainstorm Team:
I am learning EEG Source imaging problem ,but I find that When I used wMEM imaging, the wMEM method failed to show the activation region at each sample point compared to sLORETA,but the sLORETA showed it clearly.!
BLIU!

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3

Hello,

In general, for any source map, if all the sources have a null amplitude at one time instant, then Brainstorm will not display them at this particular time instant.

In your specific case with wMEM, you had to specify a reconstruction time window (in the options panel: "Data definition" / "Time window").
Outside of this time window, all the sources have a null amplitude and as a result Brainstorm will not display them.

So with your two maps displayed, if you change the current time instant (by using the keyboard arrows for instance), then the MEM-map will start showing some colors.
But the current time instant needs to be within the specified reconstruction time window.

If you still don't see anything as you move along time, then there might be another problem (for instance a custom color map was defined or the presence of NaN values...), let me know.

Blessings,

4

Hello,
I did it again, but it still didn't show the active area.

5

Hello,

We can start investigating, to quickly check if the map has some values:

Display the wMEM-map, right click on the figure, select: "Colormap: Sources", then "Maximum: Global".

Check on the bottom right side of the figure if the colormap displays a range or if it displays Invalid scale.

help-bst-1

6

thanks for your reply.aa

7

This tells us that your map contains non-null values, we can try to check where they are.

But first, I would like to make sure that small activated regions are not hidden.
Keeping the figure opened, could you select the "Surface" tab in the Brainstorm sub-panel on the right side and check "Min size":

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If "Min size" is too large, small activated regions will be hidden.

8

You should also make sure the amplitude threshold is low enough to display some values on the cortical maps:
https://neuroimage.usc.edu/brainstorm/Tutorials/SourceEstimation#Display:_Cortex_surface