FIG 1. MR signal time courses for parenchyma, sulcal veins, and bridging veins for single subject in two different functional runs (hand clenching) (S1). Each diamond represents MR signal at one time-point. Temporal resolution of the sequence was 2.2 s/image. Mean percent signal changes increase as a function of vessel size. Note low test-retest variability of percent signal changes within the same subject.