During a visual cognitive task, the regions of the cortex associated to visual processing respond to the incoming stimuli. This reaction involves a hemodynamic response (BOLD response) typically measured using fMRI. As the BOLD response is dependant of the vascular changes, a knowledge of the underlying structure is therefore mandatory. This figure illustrates the veins (acquired from SWI, blue) and arteries (acquired from ToF, red) feeding the BOLD activated region (yellow) associated to a visual task.