[MINC-users] cortical thickness normalization

[Jason Lerch]

Hi Morgan,

that was an abstract first-authored by Yasser Ad-Dab'bagh, and I indeed 
believe that the main conclusion still holds. (I can send you the PDF of 
the abstract if you like). There is no relationship between the 
thickness of the cortex and overall brain size- normalization thus 
artificially distorts the thickness rather than compensating for a 
simple scaling factor.

This argument even extends across evolution - compare the thickness of 
the mouse cortex, which is around 0.9mm, or about 3 times smaller than 
human cortical thickness, to the difference in overall brain volume 
(several orders of magnitude).

Cheers,

Jason

Morgan Hough wrote:
 > Hi there,
 >
 > I just wanted to see if anyone remembers the HBM abstract that Bruce is
 > referring to here regarding cortical thickness normalization. Does
 > anyone have a different opinion on this matter? Thanks in advance for
 > your time.
 >
 > Cheers,
 >
 > -Morgan
 >
 >
 >   Re: [Freesurfer] cortical thickness normalization
 >
 > Bruce Fischl
 > Mon, 07 Jan 2008 09:21:28 -0800
 >
 > Hi Paul,
 >
 >
 > I think volume you can normalize with eTIV, but how to normalize
 > thickness is an open question. You could argue it should be eTIV^(1/3),
 > but I know at least one HBM abstract a couple of years ago from the MNI
 > showing that you shouldn't normalize at all. If your effects are focal
 > then normalizing by avg thickness is reasonable, or maybe the average of
 > some region that you expect to be unaffected?
 >
 > cheers,
 > Bruce
 >
 >
 >
 > On Mon, 7 Jan 2008, Paul Greenberg wrote:
 >
 >     Dear Freesurfers,
 >
 >       
 >
 >     When comparing cortical gray matter volumes between groups it is
 >     appropriate to normalize subject's mean cortical volume in each
 >     cortical parcellation by their eTIV. Is there a corresponding value
 >     appropriate for normalizing cortical thickness? Would mean cortical
 >     thickness for a single hemisphere be an appropriate normalization
 >     factor? We are interested in comparing cortical thickness between a
 >     control group and a group of people with a degenerative brain 
disease.
 >
 >     Thanks very much,
 >     Paul
 >
 >
 >
 >       
 >
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