Hi Tim + Matt +all.
With regard to this notion of thresholding as a
consistent % of the waytotal number: Roughly what kind of numbers have
people been using to do this? I know you need to choose one that looks best,
etc., but I'm wary of being too 'liberal'...
In Matt & Tim's nature neuroscience paper (Rilling et al. 2008), they
threshold to include only those voxels that received 'at least 0.000038% of
the total streamlines sent out from the ROI masks'. Now, given that the
analogy has been made several times on this mailing list between
thresholding as a proportion of the number of seed voxels and thresholding
as a proportion of the number of streamlines passing between two seeds (i.e.
the waytotal number) - would it be ok to threshold my results at values as
low as 0.000038% of the waytotal?
Could anyone point me to some papers that have used this thresholding as a
proprtion of the waytotal approach?
Finally (and sorry if this is a really dumb question...) - One suggestion on
this list has been to normalize probtrackx results by diving by the waytotal
number (which I read as 'fdt_paths -div (waytotal)'), whilst others have
been to threshold as a consistent % of the waytotal number (which I read as
'only include intensities greater than or equal to [(waytotal / 100)*(e.g.)
10]'). Are there any important differences between these?
Thanks,
John
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