Scout function Phase Locking Calculation different results

[fvdb]

Hello,
I have a question regarding the scout function in terms of the Phase Locking Value calculation.
I want to investigate the PLVs in two different networks. First, I use the 68 ROI of the Desikan Kiliany Atlas and second, I use 14 ROI which are also regions of the Desikan Kiliany Atlas but serve as a subnetwork of the whole brain.
For each participant, I calculated the sources over four segments, calculate the PLV for each segment and average the four PLV matrices in the end.
Now, I am wondering why the PLV values of the 14 ROI PLV matrix differ from the same 14 regions included in the 68 ROI matrix. In the PLV setting a used the setting “when to apply scout function: before”. The question is, why do the values differ although the underlying sources are the same?

Thanks in advance for the help!

[Francois]

Can you explain better what differs with what, while it should not?

Below: Example with the tutorial dataset, with 68 and 14 scouts.
The values for the same pairs are strictly the same in the two files, whether there are more or less scouts in the file.

[fvdb]

Unfortunately, in my dataset, it is not the same.

First, I used the 68 scouts:

[fvdb]

And second, I used 14 scouts (which are also contained in the 68 scouts):

[fvdb]

But the results in the PLV values in the excel file differ. To show the differences, I extracted the values from one scout in relation to the others:

First, out of the 68 ROI matrix (the highlighted values are the 14 scouts which I used in the other calculation):

[fvdb]

And second, the results when I just use the 14 scouts:

[Francois]

I tried to reproduce exactly what you did:

• Copy the same subset of DK scouts to a new atlas
• Compute the PLV for a single file using both the full DK atlas and the subset
• Export the first frequency band to a XLSX file

I obtained exactly the same values for the same couple of ROIs (see screen captures below).

Make sure that:

• You use the same files
• You used the same options
• You did not alter the DK scouts in your modified atlas
• You exported the same frequency band to the .xslx file

[fvdb]

You are right. When I selected the 14 scouts of the desikan-killiany atlas in the PLV Setting window, my results are the same too. But this is not the way how I did it. I created a completely new atlas only with the 14 regions:

And in the PLV setting window, I selected this specific atlas (Desikan_Killiany_09). When I do that, I got the results I posted before.

[Francois]

@fvdb

But this is not the way how I did it. I created a completely new atlas only with the 14 regions

This is what I did:

[fvdb]

Now, I tested everything systematically and noticed that there was a mistake in the "new atlas". I used the exact same scouts, but now, after I created it new again, my results are the same, too.
Thanks for your help. It was good to know that the results should be the same. Whatever the bug was, now it is fixed.