Chunk #44 — 4 Discussion — 4.2 EEG discriminating components during the P3 and around reaction time reveal a period of transition from externally driven task-related to internally-driven processing
Reports of BOLD activations in draining veins are also rare in the literature, due to the high spatial resolution required to differentiate veins from cortical tissue. However,Bianciardi et al. (2011), using a high-resolution study of visual areas at 7 T, found task-related negative BOLD correlates in large cerebral veins. We found a remarkable 340-voxel cluster that is adjacent to the precuneus but appears to track the superior sagittal sinus, a large cerebral vein that drains widespread areas of cortical tissue. The BOLD signal we detected in cerebral veins is likely due to a transient misbalance between metabolic demands and increased oxygenated blood, and may reflect strongly activated cortices that are functionally but not anatomically overlapping across subjects, but which drain into the same veins. Since the superior sagittal sinus is nearly exclusively responsible for draining the cerebrum (Mattle et al., 1990), this interpretation does not allow speculation regarding particular cortices. An alternative idea for the physiological meaning of this activation is that it reflects a global change in cerebral blood flow. Given the care we took with image registration, pulsation
