Hi Marine, these are two different analyses. In the first analysis, you have used a voxel-wise analysis, and in the second you've done an ROI analysis. They are not guaranteed to give the same results. Also, it is possible that the actual GLM design matrices are different. QDEC will create a file called Xg.dat with the design matrix. You should make sure it is the same as that produced by R (this has been a problem in the past when people tried to do comparisons).

doug

On 11/23/2016 06:21 AM, Lisa Delalande wrote:

Hello, As a PhD student, I send you this mail because i am meeting a misunderstanding with QDEC. In a few words : I made an analysis thanks to the QDEC tool :

• I tested a correlation between an inhibition score and cortical thickness, corrected for age

(continuous = inhibition score ; nuisance = age ; smoothing = 25 and FDR corrected)

--> thus, it highlighted a correlation between our inhibition score and cortical thickness in right medial orbito-frontal area.

• then, I realised a ROI analysis. I extracted different statistic values from this orbito-frontal region following your wiki (aparcstat2table).

  Thus, I obtained for each participant, the average value of medial orbitofrontal cortical thickness.

  Finally, I made a multiple linear regression analysis on R software which is a statistical software. Surprisingly, « R », indicated that it doesn’t exist any correlation between the right medialorbito frontal thickness values and the inhibition scores. I don’t understand why.

  Can you help shed some light on this issue ?

Yours sincerely

Marine Moyon

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