Perfect!  Thanks, Alfonso. 
 
It was the normalization of the r2 values that hung me up, though conceptually now I'm trying to get my head around the physiological meaning of a blob that is task-associated "below-average" for all conditions but varies in "below-average" strength between groups and over time [i.e., one group demonstrates a significant reduction in "below-average" (improvement?) for the condition over time, such that it is strongly below-average at baseline and less so at follow-up -- that is closer to mean zero].
 
Warm regards,
Jeff