Hello Dr. Greve,

I am normalizing the cortical SurfArea features from both ?h.aparc.stats with the total white matter surface, calculated as the sum of the total of the two hemispheres. I checked my results and after applying a t-test I saw the difference between normalizing and not normalizing was not significant, although I expected an improvement after normalization. I also checked an old conversation in the archive about a close topic, sorry for the naive question, but could there be a "global effect" as mentioned in the conversation for the surface measurement? wouldn't it affect both, the total wm measurement and the cortical surface measurements?

Thanks for your answer!

El mar, 31 may 2022 a las 17:11, Douglas N. Greve (<dgreve@mgh.harvard.edu>) escribió:

What surface feature are you exvaluating? If thickness, then don't do normalization by eTIV or surface area or anything else

On 5/23/2022 11:20 AM, Rafael Navarro wrote:
        External Email - Use Caution

Hello FreeSurfer Developers,

I am building a brain age model from the stats extracted with FreeSurfer. I tested my model normalizing volumes by eTIV, which I think is the recommended, and surfaces by WM total surface. For surfaces, I haven't found any recommendations. I am getting better results by using the features without normalization.

From what I have read, volume normalization clearly should be performed, but I am in doubt about the surface normalization. Although, the surface is different depending on head size and along with lifespan, I am not sure if all cortex surfaces evolve the same way, and therefore that normalization might be adding noise to my results. Then, is it correct to normalize my surface features by the total WM surface? Does anybody know any reference that talks about the topic or have done similar work?

Thank you for your support

-----------------------------------
||  Rafael Navarro González
||  Ph.D. Student
||  ETSI Telecomunicación
||  Universidad de Valladolid
||  Campus Miguel Delibes
||  47011 Valladolid, Spain
||  e-mail: rafael.navarro@uva.es
||  Phone: +34 672 394 294
||_________________________________
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