sEEG sensitivity map export

Squiyk · June 12, 2025, 12:37pm

Hello everyone,

I'm interested in exporting the sEEG leadfield sensitivity map to a surface map I could work with afterwards as a brainstorm object. Is there any way to do this currently?

Thank you in advance for any insight you may have on doing this!

Raymundo.Cassani · June 12, 2025, 1:41pm

Hello @Squiyk,

You can check how is the leadfield sensivility computed from the Gain (stored in the Head model file) for one or all sensors. This is variable normLF in the function UpdateLeadfield() in view_leadfield_sensitivity.m

github.com/brainstorm-tools/brainstorm3

toolbox/gui/view_leadfield_sensitivity.m

master


      
          
          %% ===== COMPUTE MRI INTERPOLATION =====
              function ComputeMriInterp()
                  MriOptions = bst_get('MriOptions');
                  GridSmooth = 1;
                  grid2mri_interp = grid_interp_mri(HeadmodelMat.GridLoc, sMri, [], 1, MriOptions.InterpDownsample, MriOptions.DistanceThresh, GridSmooth);
              end
          
          
          %% ===== UPDATE LEADFIELD =====
              function UpdateLeadfield()
                  % Compute sensitivity
                  bst_progress('start', 'View leadfields', 'Computing sensitivity...');
                  % Sum all the channels
                  if (iChannel == 0)
                      if isAvgRef
                          LeadField = bst_bsxfun(@minus, GainMod, mean(GainMod,1));
                      elseif ~isempty(iRef)
                          LeadField = bst_bsxfun(@minus, GainMod, GainMod(iRef,:));
                      end
                      LeadField = reshape(LeadField, size(LeadField,1), 3, []); % each column is a vector

The variable nornLF contains the leadfield sensitivity for each point in the source grid.

Squiyk · June 16, 2025, 4:56pm

Thank you for the quick reply!

[This post was split]

Raymundo.Cassani · June 16, 2025, 4:59pm

A post was split to a new topic: Issues with OpenMEEG BEM headmodels for sEEG data

tmedani · June 16, 2025, 8:35pm

please note that the sensitivity is computed for a pair of sensors for EEG/iEEG.
you can set the reference channel to an average and then you can have a full sensitivity wtr to the avg ref.