[FieldTrip] Beamformer results for simulated data

[IMALI THANUJA HETTIARACHCHI]

Dear fieldTrip Users,

I am trying to run a dipole fit with the nonlinear grid search and a beamformer scan on a simulated data set, to compare the results.

My simulated dipole is at the MNI coordinates [32.8 -85.8 28]. It is shown in red in DIP_1.jpg. The ft_dipolefitting results for the simulated dipole is in green in DIP_1.jpg.

When I do the lcmv beamformer scan on the same simulated data and plot them I get results as in POW_1.jpg for avg.pow parameter and NAI_1.jpg for avg.nai parameter. Following is the code I use for the above purpose;

cfg = [];
cfg.vol = curry_vol;
cfg.elec = sens;
cfg.grid=template_grid;
cfg.method = 'lcmv';
cfg.lambda='5%';
cfg.projectnoise='yes';
source = ft_sourceanalysis(cfg, timelock);

load standard_mri.mat
mri = ft_volumereslice([], mri);
%% Figure POW_1.jpg
% Aligning the measure of power increase with the structural MRI of subject
cfg=[];
cfg.downsample=2;
cfg.parameter='avg.pow';
source_int=ft_sourceinterpolate(cfg,source,mri);
% Plot the interpolated data
cfg=[];
cfg.method='slice';
cfg.funparameter='avg.pow';
figure,ft_sourceplot(cfg,source_int)
%% Figure NAI_1.jpg
% compute the neural activity index, i.e. projected power divided by
% projected noise
sourceNAI=source;
sourceNAI.avg.nai=source.avg.pow./source.avg.noise;  %neural activity index calculation
cfg=[];
cfg.downsample=2;
cfg.parameter='avg.nai';
sourceNAI_int=ft_sourceinterpolate(cfg,sourceNAI,mri);

cfg = [];
cfg.method = 'slice';
cfg.funparameter = 'avg.nai';
cfg.maskparameter=cfg.funparameter;
figure ,ft_sourceplot(cfg, sourceNAI_int);

Can you please direct me to what I am doing wrong or missing in my code to get sensible beamformer scan results.  When I read the source_int.avg.pow and sourceNAI_int.avg.nai most of the values are NaN's.

Many amny thanks in advance.

Regards
Imali

Imali Thanuja Hettiarachchi
PhD Candidate
Centre for Intelligent Systems research
Deakin University, Geelong 3217, Australia.
Email: ith at deakin.edu.au<mailto:ith at deakin.edu.au>
www.deakin.edu.au/cisr<http://www.deakin.edu.au/cisr>

[Description: Description: Description: cid:1216BE20-1800-4A47-8B9F-E7B9D94831CD at deakin.edu.au]




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