Synthetic EEG making

Discussions
1

hi
I am a beginner with this toolbox.
I was wondering if it is able to make synthetic multi channel EEG for my simulations.
thanks

2

Hello,

Yes, you have few processes in the “simulate” menu to generate signals and save them as recordings or source maps.
You can define a few signals, associate them to regions of interests (scouts) then use the synthetic brain activity to simulate the corresponding EEG signals. In input, you need a channel file corresponding to the electrodes cap you want, and a noise covariance matrix with properties of the signals you want to generate.

Before going into more details, I recommend you follow carefully the 12+3 introduction tutorials, as they introduce all the concepts you will need for doing this.
Additionally you can read the EEG/Epilepsy tutorial, because it is the only tutorial that talks about EEG.

Cheers,
Francois

3

thanks a lot for help

4

Dear Francois,
I am new to BST. I have gone through 12+3 tutorials. My Aim is to generate simulated EEG data. I have following things 1. Source time series (simple matrix of size 3 x 500 in Matlab with kind of response I want – 500 time points) 2. Coordinate in MNI space of 3 points in cortex where I want this matrix of 3x500 to be associated 3. EEG electrode cap 4. I will use default anatomy(colin27 in BST). Now I want to associate time series to 3 points in MNI space then perform forward modeling to generate SCALP EEG recordings.
I can associate them to scouts but how can I associate to specific points or vertex as per MNI coordinate and proceed.
Currently I am importing from a user matrix of my simulation. Add this to Process then “simulate recording from scout” in windows select 3 scout from list and run batch. It generates scalp. But my requirement is to associate them to the points in MNI space. Can you please help with these questions? Thank in advance.

5

Hello,

The procedure looks good, but there is no way to directly find the surface vertex corresponding to a point in MNI coordinates. You have to manually:

  1. Convert your desired MNI coordinates to the equivalent in SCS coordinates (MNI > MRI > SCS)
    I’ve just added a small function cs_mni2mri to convert easily from MNI to MRI coordinates (then you can convert from MRI to SCS). See the examples at the bottom of the following page:
    http://neuroimage.usc.edu/brainstorm/CoordinateSystems

  2. Then look for the closest point in the surface vertices:

  • export the surface to Matlab: right-click on the surface > File > Export to Matlab > sSurf
  • dist = sqrt(sum(bst_bsxfun(@minus, sSurf.Vertices, Pscs).^2, 2));
  • [mdist, iVert] = min(dist);
  • create a scout, export it to Matlab: tab Scout, menu Scout > Export to Matlab > sScout
  • sScout.Vertices = iVert; sScout.Seed = iVert; sScout.Name = ‘whatever’;
  • import the scout back in the Scout tab (Scout > Import from Matlab > sScout)

Francois