Hi Doug

 

I hope it’s okay that I double check I’m doing the correction over 2 hemispheres correctly and ask a question regarding correction for multiple comparisons. I will briefly describe what I have done:

 

I have 2 groups of subjects – Drug addicts (n= 17) and controls (n=20).

 

1.       I ran a surface thickness study:

 

·         For the ‘mri_glmfit’ command, I used DOSS and specified a contrast of +1 -1 0 (Controls > MA)

·         I ran a pre-cached simulation with the following command: mri_glmfit-sim --glmdir lh.group_age.glmdir --cache 4 pos

·         This simulation should only have corrected for the left hemisphere as I understand it. My cluster summary text file showed me that a cluster survived in the insula. I interpreted this as ‘controls had higher grey matter thickness in this cluster located in the insula than drug addicts’. However, this was only corrected over the left hemisphere (when I ran the same simulation in the right hemisphere, nothing survived multiple comparison correction).

·         I now wanted to correct the lh results for 2 hemispheres. From the help menu of ‘mri_glmfit-sim’, I understood you can do this in 2 ways, are both of these correct and give the same result?

a.       mri_glmfit-sim --glmdir lh.group_age.glmdir --cache 4 pos --2 spaces --no-sim csdbase

b.      mri_glmfit-sim --glmdir lh.group_age.glmdir --cache 4 pos --cwpvalthresh 0.025

 

Ø  No clusters survived the Bonferroni correction over both hemispheres. So I assume I can no longer report this result?

 

2.       I ran a subcortical volume study:

·         I used SPSS to perform the statistical analysis on each of 14 subcortical structures (left and right). Is there a good way to correct for multiple comparisons, apart from Bonferroni, which would be very conservative?

 

Many thanks for your advice.

 

Kind regards

Reem

 

 

Reem Jan

BPharm (Hons), RegPharmNZ

 

PhD Student / Pharmacist

School of Pharmacy, Faculty of Medical & Health Sciences,
The University of Auckland, Private Bag 92019,
Auckland, New Zealand. 

Ph: +64 9 373 7599 ext 81138. DDI: +64 9 923 1138

F: +64 9 367 7192

 

 

 

 

Sorry, not possible.

On 7/19/12 6:56 PM, Caspar M. Schwiedrzik wrote:

Hi!
Is it possible to have slice-by-slice predictors in Freesurfer, and if so, how?
Thanks,
Caspar

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