All voxels in the whole brain show above chance level in TDT result

Hello TDT users,

I have 16 beta images for each of the 3 conditions across four runs per subject, which were used as the input for individual’s searchlight analysis.
I predicted that some decodable regions will show positive value in the file ‘res_accuracy_minus_chance.nii’, but all voxels in the whole brain show above chance level in TDT results unexpectedly. (I uploaded the file as example.)
So, I wonder if this result is valid, or if I set wrong parameters for decoding analysis.

The parameters that I used is as below:

cfg = decoding_defaults(cfg);
cfg.testmode = 0;
cfg.analysis = decoding_type;

cfg.decoding.method = ‘classification_kernel’; = ‘libsvm’;
cfg.decoding.train.classification.model_parameters = ‘-s 0 -t 0 -c 1 -b 0 -q’; = spm(‘ver’);

cfg.results.dir = output_dir;

cfg.searchlight.radius = 12;
cfg.searchlight.unit = ‘mm’;

cfg.files.mask = fullfile(mask_dir); = alldesign(:,1);
cfg.files.label = cat(1, alldesign{:,2});
cfg.files.chunk = cat(1, alldesign{:,3});
%(I checked that the beta images are allocated well in the design matrix.) = make_design_cv(cfg);
cfg.results.output = {‘accuracy’,‘accuracy_minus_chance’};

results = decoding(cfg);

Any feedback would be great, Thanks!

~ Taehyun Yoo

Answer can be found here: