Dear Vladimir,
Could you please let me know how to do the following:
1: Find the MEG sensors closest to a set of fMRI activations in MNI space.
2: Find the MEG sensors that will be most affected by activity at a given MNI location, according to the lead fields.
I want to do this at a group level (i. e. pick a set of channels to use for all subjects) - so I think the best thing to do is make the calculation for the template sensor coords that each subject is coregistered to. Do you agree?
This is what I have so far for 1:
D = spm_eeg_load(file);
sens = D.sensors('MEG');
chanpos = sens.chanpos';
srcpos = [-8, -88, 4]'; % example source ROI
% Find the Euclidean distance (dist) and index (idx) of the closest sensor to that location.
[dist,idx] = min(sqrt(sum((chanpos- repmat(srcpos,1,length(chanpos)) ).^2))) ;
Does this look correct?
For 2, I'm not really sure of the best way to do this. Obviously source configurations and strengths would have a large influence on sensor sensitivities. I imagine the only way that these estimates would deviate from the nearest channels would be when orientations are constrained by the cortical mesh (an interesting comparison to make, I think). Could you think of any simple summary measures that would capture this?
Thanks,
John
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