Simulating EEG spikes using head model and chosen dipoles

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Hi Francois,

I had a quick question about using Brainstorm in forward modelling to obtain simulated EEG data. My current goal of my study is to implement a simulated EEG spike based off of a manually chosen dipole (I may want to expand to multiple dipoles but a single dipole will work great for now!)

As of now I am using the ICBM152 template and I am importing a standard 10-20 19 electrode setup, as that is the data I am working with. I have currently generated the BEM head model, registered the electrodes into the surface, and computed the forward model to obtain the Gain matrix for the forward solution. After this, I want to manually select a dipole and generate a field from this to generate a spike.

Is there any way you would suggest doing this? I have defining source activity and creating a scout but I was unable to get the simulation of the scout to work.

Let me know what you think, thanks for your help!
huderek5

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I want to manually select a dipole and generate a field from this to generate a spike.

Have you checked these tutorials and forum posts?
https://neuroimage.usc.edu/brainstorm/Tutorials/Statistics#Simulate_recordings_from_these_scouts
Simulate sources using brain template and CTF-275

Is there any way you would suggest doing this? I have defining source activity and creating a scout but I was unable to get the simulation of the scout to work.

What kind of problem did you have?
Can you post a precise description of what you had, what you tried to do, and what fails? Screen captures would help (ALT+PrintScreen and CTRL+V in this forum directly)

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Hi Francois,

Thank you for the reply! I managed to get the user scout made and I can generate simulated EEG.
I had a few other questions about the scout and source activity EEG inputs:

  1. For the inputted source activity, is there anyway for brainstorm to simulate generic EEG signals or upload them rather than creating a generic signal? I am currently using white noise EEG.

  2. For the scout size, is there a way to input a specific dipole orientation and direction? I have only been able to alter the scout size and change the patch. My goal is to input a single MNI coordinate, followed by the orientation and length of the dipole.

  3. For the scout, is there a way to increase the strength or effect of the dipole? I want to see what properties of the scout I can change to alter the properties of the epileptic spike.

Let me know when you can, thanks again!
huderek5

4

For the inputted source activity, is there anyway for brainstorm to simulate generic EEG signals or upload them rather than creating a generic signal? I am currently using white noise EEG.

There is not more in Brainstorm than what you can fin in the process menu "Simulate".
You could use source signals generated with the analysis of this tutorial dataset: https://neuroimage.usc.edu/brainstorm/Tutorials/Epilepsy
But if you use it, for other purposes than testing and learning Brainstorm (ie. for actual research based on this data), you should contact the authors of this dataset first (as mention in the LICENSE section of the tutorial).

You can replace the signals in the file with anything you want. Right-click ot the simulated signals > File > Export to Matlab, modify the .Value field, right-click on the FOLDER > File > Import from Matlab.
https://neuroimage.usc.edu/brainstorm/Tutorials/Scripting

For the scout size, is there a way to input a specific dipole orientation and direction? I have only been able to alter the scout size and change the patch. My goal is to input a single MNI coordinate, followed by the orientation and length of the dipole.

Either you can edit manually the cortex surface if you want to use cortically-constrained source models (modify the Vertices and VertNormals fields):
https://neuroimage.usc.edu/brainstorm/Tutorials/ExploreAnatomy#On_the_hard_drive:_Surface

Or you can create you own grid of source points and use this in input of the computation of a volume source model:
https://neuroimage.usc.edu/brainstorm/Tutorials/TutVolSource

For the scout, is there a way to increase the strength or effect of the dipole? I want to see what properties of the scout I can change to alter the properties of the epileptic spike.

Increase the strength of the value is equivalent to increasing the simulated signal you created initially (multiply one of the rows of the .Value field with whatever scalar you want).
Changing the orientation is possible only with source models constrained to the cortex. It corresponds to modifying manually the VertNormals field in the surface file. Not straightward...

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Hi Francois,

Thanks for the response, I'm pretty sure I know how to go about this now knowing how the dipole is chosen based on the scout.
I'll let you know if I need anything else,

Best,
huderek5

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FYI: To address all the recent questions we had related with simulations, I added some code in Brainstorm and wrote a new tutorial:
https://neuroimage.usc.edu/brainstorm/Tutorials/Simulations

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Just committed a new process "Simulate recordings from dipoles":
https://neuroimage.usc.edu/brainstorm/Tutorials/Simulations#Single_dipoles

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