[FieldTrip] Beamforming / ft_sourceplot: Different results between 3D-Surface Plot vs. 2D-Slice/Ortho Plot

[Brilliant.OE8891 at mh-hannover.de]

Dear Fieldtrip community,

My name is Brilliant (yes, it's my real name :)) and I am a PhD Student at Kral Lab at Hannover Medical School, Germany.
I am currently doing Time-Frequency Analysis on EEG-Data and am trying to compute the Source Reconstruction with the Beamforming in Fieldtrip.
The EEG-Data were collected in experiments, which the participants listened to auditory stimuli and had to respond by pressing a button.
In the Grand-Mean of the Time-Frequency Plot Alpha desynchronization were observed and we would like to know the source/s.

When observing the figures from the result of Source Reconstruction via Beamforming, it seems like the 3D-Surface Figure (Figure A) does not correspond well with the 2D-Slice Figure (Figure B).
For example in the 3D-Surface Figure, we could not see the strong projection on left occipital hemisphere although in the 2D-Ortho Figure it can be seen (Figure C).
I play around with the parameter of the 'cfg.projthresh', but still cannot see the source activation in the 3D-Surface Figure as clearly as in the 2D-Figures.
Another question related to this is why we don't see much activation in the auditory cortex.

The code that I use to plot the results are as follow.

Any feedbacks and suggestions would be appreciated.
Thank you and kindest regards.

Brilliant

---

source_diff_mni          = source_diff;  %Calculated power difference
source_diff_mni.coordsys = 'mni';        %Label the coordinate system as 'mni'
absPows = abs(source_diff_mni.avg.pow);  %Check the maximum power
maxPow  = max(absPows);
maxPow  = round (maxPow,2);

% Plot 3D
cfg = [];
cfg.method         = 'surface';
cfg.funparameter   = 'pow';
cfg.projmethod     = 'nearest';
cfg.surfinflated   = 'surface_inflated_both_caret.mat';
%cfg.projthresh     = 0.5; %more mean less projection
cfg.funcolorlim    = [-maxPow maxPow];
cfg.camlight       = 'no';
ft_sourceplot(cfg, source_diff_mni);

brainnetome = ft_read_atlas('BNA_MPM_thr25_1.25mm.nii') %Load Atlas
atlas = brainnetome;
mri = ft_read_mri('Subject01.mri'); %Load MRI

% Interpolate the source_diff_mni to the MRI
cfg = [];
cfg.voxelcoord      = 'yes';
cfg.parameter       = 'pow';
cfg.interpmethod    = 'cubic';
source_diff_mri = ft_sourceinterpolate(cfg, source_diff_mni, mri);

% Plot 2D
threshold = 0.3*maxPow; %Masking to not show any power below 30% max power
threshold = round(threshold,2);

source_diff_mri_mask = source_diff_mri;
source_diff_mri_mask.mask = (source_diff_mri_mask.pow>threshold & source_diff_mri_mask.pow<maxPow) | (source_diff_mri_mask.pow<-threshold & source_diff_mri_mask.pow>-maxPow);

% Slice 2D-Plot
cfg                  = [];
cfg.method           = 'slice';
cfg.atlas            = atlas;
cfg.anparameter      = 'tissue';
cfg.maskparameter    = 'mask'
cfg.funparameter     = 'pow';
cfg.interpmethod     = 'cubic';
cfg.funcolorlim      = [-maxPow maxPow];
cfg.nslices          = 9;
cfg.slicedim        = 1; %Slice Sagital
ft_sourceplot(cfg,source_diff_mri_mask);

% Ortho 2D-Plot
cfg                 = [];
cfg.method          = 'ortho';
cfg.atlas           = atlas;
cfg.maskparameter   = 'mask'
cfg.funparameter    = 'pow';
cfg.interpmethod    = 'cubic';
cfg.location        =  [-3 -47 68]; %Right STG 41/42
cfg.funcolorlim     = [-maxPow maxPow];
ft_sourceplot(cfg,source_diff_mri_mask);

---

Brilliant, M.Sc.
Pronouns: he, him, his

Medizinische Hochschule Hannover
Institut für AudioNeuroTechnologie (VIANNA)
OE 8891, M20, Ebene 01, Raum 1640
Stadtfelddamm 34
30625 Hannover

Tel.: +49 511 532-1532 (EEG-Labor)
Email: brilliant.OE8891 at mh-hannover.de<mailto:brilliant.OE8891 at mh-hannover.de>
Web: www.neuroprostheses.com<http://www.neuroprostheses.com/>

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