Hi Alfonso,

I recently ran an analysis that included two sessions (task/rest) for each subjects and two 2nd level covariates that group the subjects based on the stimulus modality they received. After completing the analysis, I took the 'ROI.mat' file from the one of the contrasts in the secondlevel results directory. 

I notice the 'h' field in this structure, which I understand to be the Fischer-transformed correlation coefficients. My question is, which connections do these correlations describe? Even though there are multiple possible contrasts comparing the sessions and the within-subjects effects, should there not be four sets of correlation values? How do correlation coefficients change across contrasts?

Any help would be much appreciated. Thank you!

Hi Suneel,

In general the ROI.h field represents the "contrast values", determined by a linear combination of the second-level GLM regressor coefficients as determined by your between-subjects contrast vector/matrix.

In particular, in your analysis ROI(i).h(j) represents the difference between the two groups (Visual - Auditory) in the difference between conditions (task - rest) in the connectivity between the i'th and j'th ROIs

i.e. ( connectivity@Task_Visual - connectivity@Rest_Visual ) - ( connectivity@Task_Auditory - connectivity@Rest_Auditory )

Best
Alfonso
Originally posted by Suneel Banerjee:

Thank you so much for the clarification! When looking at the ROI.h field for in a project with just a single session and no between-subjects contrasts, would this simply be the Fischer-transformed correlation coefficients between the ROI time series?