Fig. 2

First column shows of the identified voxels in the brain associated with activity curves for participant 6 at four different threshold levels (\(a1=0.4, 0.5, 0.6\) and \(0.9\) when \(a2=0.9\)). Second column shows the clustered activity curves with early and late peaks, respectively, labelled as arteries (green lines) and veins (blue lines). The maps in third and fourth columns show the location of the curves back onto the anatomical regions from which they were extracted, clearly showing the location of large arteries (green pixels) and large veins (blue pixels)