A, Lateral view of the brain with a window centered at the level of the intraparietal sulcus (IPS). Using the transillumination technique, the last lower layer of sagittal stratum fibers corresponding to optic radiations is shown. The vertical fibers where the illumination intensifies correspond to the tapetum fibers. Through the transillumination, the surface of the atrium is drawn. All the labeling comes from previous knowledge. B, After removing a large part of the sagittal stratum fibers and its corresponding optic radiations, we could get a better vision of the vertical tapetum fibers. (Images courtesy of E de Oliveira)