eeg_positions

Description

Calculates the 10/10 EEG positions based on 4 fiducial points based on the UI 10/10 definition provided in (Jurcak et al., 2007).⁠

Usage example

  1. Open a terminal and go to the directory of the “Ernie” example data set.

  2. Open the mesh file in the GUI

simnibs_gui ernie.msh

  1. Visually determine the positions of the nazion (Nz), left preauricular point (LPA), right preauricular point (RPA) and inion (Iz) on the skin surface and click on them to get their positions. Write down the coordinates displayed in the bottom of the window.

  2. Run using the coordinates taken in step 3

eeg_positions -m ernie.msh -o ernie_10_10 -Nz 1.6 97.1 3.4 -LPA -82.2 -14.3 -22.2 -Iz -4.8 -108.8 -32.7 -RPA 79.7 -18.9 -24.6

  1. Two files will be created: ernie_10_10.csv and ernie_10_10.geo

  2. Check the positions by opening the mesh file in Gmsh, going to File → Merge and opening the ernie_10_10.geo file for a visual check of the electrode positions

  3. ernie_10_10.csv is a text file containing names and positions of the EEG electrodes. For now, you have to manually enter these coordinates when defining electrodes in simnibs_gui. Alternatively, you can write your own matlab- or python-script that uses the positions to create a .mat-file with the simulation information.

Further notes

  • We have compared positions obtained using this procedure against positions automatically obtained from MNI electrodes definitions and found no large differences (Saturnino et al., 2018). The later are automatically calculated during our head meshing programs headreco and mri2mesh and stored in the m2m_subID/eeg_positions/EEG10-10_UI_Jurak_2007.csv file.