Functional anaysis in anatomical ROIs, freesurfer

Dear Sisters and Brothers in neuroscience,

I have a question regarding functional analysis in freesurfer. I have all my functional and anatomical data analyzed using fsfast pipeline. I have contrasts for each participant. Now I would like to extract the functional activity from anatomical regions (from the HCPMMP1 atlas)

I would like to be able to get the % signal change in a chosen contrast in my model from a chosen anatomical label. I have the atlas in each subject’s space. I am sure there is an easy way to do what I need, but I am lost in the FS’s documentation. Should I use mri_segstats? If yes, how do I specify the options?

I will be grateful for your help.