Brain network connectivity with 128 channel ERP data

[yuluo]

Hi all,

I wanted to do brain network connectivity analysis after source localization.However,when I computed coherence with grand average ERP data,there was one error:

Thanks!

[Francois]

Hello,

You do not have enough memory for what you are trying to execute, you need to decrease the size of the problem. You can find inspiration from the forum, for example:

Functional Connectivity

But when I want to compute connectivity for all brain regions (NxN) I get the memory error Select the option “Use scouts” and “Apply scout function: before”. http://neuroimage.usc.edu/brainstorm/Tutorials/TimeFrequency#Scouts this error is expected for large computation, but with SPM we did this analyzing and it took sometimes about 1 day or more. Processing fMRI and EEG are two very different things. Expect much higher memory requirements with EEG. How can I interpret this 3D figure? …

Brain Regions Connectivity

I’m sorry, there are still no proper tutorials for the connectivity analysis. With the options you selected, you are trying to compute a connectivity measure for 15171x15171 pairs of signals (all the source signals). For the coherence frequency resolution you selected, this requires the creation in memory of a few matrices of about 200Gb. This is not something you can do on any computer. If you want to compute a full connectivity network for the whole brain, you need to decrease the size of th…

Coherence NxN source file errors

Hello If you have a source file with 15000 vertices and try to compute the coherence NxN for this file (sampling rate = 1000Hz), the size of the output file will be: 15000 * 15000 * 500 * 8 / 1024^3 = 838 Gb! This cannot fit in the memory of any computer… If you select all the scouts of an atlas, with the option “Scout function: After”, it will first compute this 15000x15000 connectivity matrix and then group by scouts. You can instead select a few scouts and/or use the option “Before”. Fo…

Francois

[yuluo]

Thank you for your reply,Francois!
I defined one scout, then computed coherence between the scout and the whole brain, but there seemed no connectivity.

I used the grand averaged data, maybe the epochs were not enough? Or maybe the scout I chose was not suitable?

I recorded scalp EEG, and used the default anatomy(ICBM152), and got 15000×15000 vertices, these vertices are too much for computation. Could I reduce the vertices to 4000 or less ? How to do that?
Many thanks!

[Francois]

I’m sorry, it is difficult for us to help you with this limited information. There are too many options in these connectivity processes and too many possible analysis pipelines.
Please post more detailed questions, explain exactly what you wanted to do (your hypothesis, your literature references), what you did on your data (measures, options…), what you obtained, and why this is not what you expect.