Tags: template electrode

Template 3-D electrode sets

Electrodes are represented as points in 3-D Cartesian space, i.e. with an X, Y and Z position for each electrode. Furthermore, each electrode has a label. There is a frequently asked question about how the electrode structure is described.

You can use the following snippet of code to get a quick overview of the template electrode sets.

dirlist  = dir('template/electrode/*.*');
filename = {dirlist(~[dirlist.isdir]).name}';

for i=1:length(filename)
  elec = ft_read_sens(filename{i});

  ft_plot_sens(elec, 'label', 'yes');
  grid on
  view(135, 20);
  title(filename{i}, 'Interpreter', 'none');

  [p, f, x] = fileparts(filename{i});
  print([lower(f) '.png'], '-dpng');

You can find the template 3-D electrode sets included in FieldTrip here.

The 10-20, 10-10 and 10-5 system for electrode placement

The following template electrode sets describe the 10-20 EEG electrodes and were constructed by Robert Oostenveld and described in The five percent electrode system for high-resolution EEG and ERP measurements. More details on the electrode positioning and the different naming schemes can be found in the five percent paper and on Robert’s personal blog.

The electrodes are stored in an ASA .elc file which can be read with ft_read_sens. The electrode positions are represented in mm in the MNI coordinate system and correspond to the template BEM volume conduction model detailed in this publication and that is available in the fieldtrip/template/headmodel directory as standard_bem.mat. See also this page.

  • standard_1005.elc
  • standard_1020.elc
  • standard_alphabetic.elc
  • standard_postfixed.elc
  • standard_prefixed.elc
  • standard_primed.elc

The EGI geodesic sensor net

The following template electrode sets are for the EGI geodesic sensor net and were downloaded from the EGI FTP server.

  • GSN-HydroCel-32.sfp
  • GSN-HydroCel-64.sfp
  • GSN-HydroCel-65.sfp
  • GSN-HydroCel-128.sfp
  • GSN-HydroCel-129.sfp
  • GSN-HydroCel-256.sfp
  • GSN-HydroCel-257.sfp

Note that the even versions (32, 64, 128, 256) do not include the position of the vertex reference electrode (aka Cz), whereas the odd versions (65, 129, 257) do include the position of the vertex reference electrode.

Easycap electrode arrangements

The following template electrode sets are for the Easycap electrode arrangements and were downloaded from the Easycap download page.

  • easycap-M1.sfp with full 10% system
  • easycap-M10.sfp with equidistant 61-channel arrangement