It's not fMRI. It's actually FreeSurfer values from MRI. Have a look at `TADPOLE_D4.py`, which shows the origin of `dfMri.csv` (from D4). `dfMri_D12.csv` comes from the D1/D2 dataset.
(P.S. The filename relates to an unofficial convention of naming a pandas DataFrame object with `df` and CaMeL CaSe for MRI => `dfMRI` becomes `dfMri`)