Hi experts, 

I am using the command line stream on Freesurfer for my analyses. Although I have successfully designed all my contrasts, I wanted confirmation from you regarding one contrast that I am unsure about. Will you please check if the below contrast appropriately investigates age-by-IQ interaction effects across my two groups (TD and NDDs)? 

I am also copying here information regarding my regressors and the first few lines of my FSGD file for further detail.

Contrast: To examine age-by-IQ interaction effects across groups (TD and NDDs): agexIQinteraction_acrossgroups.mtx

0 0 0 0 0.5 0.5 0.5 0.5 0 0 0 0 -0.5 -0.5 -0.5 -0.5

My regressors:

·         2 discrete factors: Diagnosis, sex

·         4 groups/levels/classes: TD M, TD F, NDD M, NDD F

·         3 continuous covariates: age, SA, IQ

 

·         Number of classes: 4

·         Number of variables: 3

 

·         NregressorsDODS= Nclasses*(Nvariables+1)= 4*(3+1)= 16

·         Regressor 1: ones for TDM subjects, 0 otherwise. Codes intercept for TDM

·         Regressor 2: ones for TDF subjects, 0 otherwise. Codes intercept for TDF

·         Regressor 3: ones for NDDM subjects, 0 otherwise. Codes intercept for NDDM

·         Regressor 4: ones for NDDF subjects, 0 otherwise. Codes intercept for NDDF

·         Regressor 5: age for TDM subjects, 0 otherwise. Codes for TDM

·         Regressor 6: age for TDF subjects, 0 otherwise. Codes for TDF

·         Regressor 7: age for NDDM subjects, 0 otherwise. Codes for NDDM

·         Regressor 8: age for NDDF subjects, 0 otherwise. Codes for NDDF

·         Regressor 9: SA for TDM subjects, 0 otherwise. Codes for TDM

·         Regressor 10: SA for TDF subjects, 0 otherwise. Codes for TDF

·         Regressor 11: SA for NDDM subjects, 0 otherwise. Codes for NDDM

·         Regressor 12: SA for NDDF subjects, 0 otherwise. Codes for NDDF

·         Regressor 13: IQ for TDM subjects, 0 otherwise. Codes for TDM

·         Regressor 14: IQ for TDF subjects, 0 otherwise. Codes for TDF

·         Regressor 15: IQ for NDDM subjects, 0 otherwise. Codes for NDDM

·         Regressor 16: IQ for NDDF subjects, 0 otherwise. Codes for NDDF

 

My FSGD file:

GroupDescriptorFile 1     

Title TD_vs_NDDs_sex_age_SA_IQ     

Class TDM     

Class TDF     

Class NDDM     

Class NDDF     

Variables age SA IQ     

Input 100092_01 TDM 0.060861784 1.747581397 0.386693428

…

 

I'd really appreciate your confirmation of my contrast, 

Thanks so much, 

Avi