Hi Tom, everyone,
Thomas E Nichols wrote:
> My comments there concern *statistic* maps, t/F/Z maps
> that come out of an analysis. The thresholding under discussion
> regards what goes *into* an analysis.
Okay, but don't you think there may be some dangers here too? For
example biasing the analysis in favour of easily-segmentable areas
against regions that are segmented with less accuracy/confidence (such
as hippocampi)?
And doesn't the comment on "sub-threshold but broad patterns"
potentially apply to patterns found in the lower probability regions
-- for example a pattern found around the outer surface of a structure?
Having just looked again at some smwc1 images, an absolute threshold
of 0.05 seems very low anyway*, it includes everything that looks like
it should be present, along with quite a bit that probably shouldn't,
so I suppose this is fairly harmless (if perhaps slightly
ineffectual). However, it didn't seem clear to me that a higher
threshold would get rid of the correct bits (at least not on my spm5
smwc1s) so I'm still not convinced that thresholding is desirable...
(*and 0.08 relative to the smwc1 mean happens to be fairly close to
0.05 in the images I've looked at, which I expect is by design!)
Thanks for your comments, Tom,
Ged.
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