• I then ran mri_glmfit-sim to identify clusters that survive multiple comparisons. This revealed 4 clusters (3 in LH; 1 in RH) that represent regions showing significant group x functioning interaction.  
• I visualized the clusters in tksurfer, and by loading the y.fsgd file was able to visualize the plotted data to get a sense of the interaction, but this is as much as I know in terms of how to examine interactions in the cluster data...... 

My specifc questions include: 

• I understand that the values in xxx.sig.cluster.mgh overlay reflect log10 p values, the signs of which indicate the direction of the relationship (i.e. -3 = negative correlation between thickness & variable) but I'm not sure how to interpret this in the context of an interaction with group?
• I understand that the values in xxx.y.ocn.dat contain the average thickness value for each subject in that cluster and that in a simple between groups test this data could be used to conduct post hoc t-tests to show the direction of the difference, but again I'm not sure how to use this data in the context of the interaction. What do the values represent in a group x variable interaction? 

Ideally, I'd like to extract the contrast estimates for each subject in the group x functioning contrast and plot it in another program and conduct pairwise comparisons (t-tests) in order to get a better understanding of the interaction). I'm not sure how to do this - is it possible? My thinking is that I do something similar in fMRI analysis in spm where I can plot the contrasts in a significant cluster and then extract both the average contrast estimates for each group and the contrast estimates for each individual subject. 

Thanks in advance! 

Laura. 

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