Hi there,
Can anyone help with the following VOI queries?
First, I am having difficulty deciding on a threshold for individual subject VOI - is there a trade-off in terms of 'quantity' (number of voxels included) and their 'quality'? Where poor quality might mean including voxels with spurious or artifactual activations.
Practicaly, thresholding with P=.1 fails to find any voxels for a substantial number of subjects, so I will need to relax this. P=.5 (or even P=1) is commonly used but seems too relaxed(?) For subjects where a robust/non-artifactual peak is identified at e.g. P=.1, won't dropping this threshold further increase the chance of finding an artifactual peak?
Second, is the amount of variance explained by the VOI a good measure of 'quality'? In which variable would this value be stored for each subject (can't find it in any of the fields of xY returned by spm_regions function)
Any help would be much appreciated!
Many thanks,
Liam
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