Anatomicoradiological Correlations Between the Tractographic and Fiber-Dissection Studies of the External and Internal Capsules. A, Coronal view of DTI-based tractography obtained with two ROIs, one at the external capsule, and the other at the posterior limb of the internal capsule. The yellow tract corresponds to the external capsule, and the red tract to the internal capsule. The putamen is located below and between where the fibers converge. The fibers of the external capsule join the fibers of the internal capsule at the superior edge of the putamen to form together the corona radiata. The fibers of the external and internal capsule do not join at the lower edge of the putamen. B, Coronal section of the right hemisphere 5 mm behind the anterior commissure. As shown with the tractography (Fig. 10A), the external capsule joins the internal capsule at the superior edge of the putamen to form the corona radiata. The external capsule is wider at the superior edge of the claustrum, and narrows as it descends along the medial edge of the claustrum leaving only a thin layer of fibers at the inferior edge of the putamen. C, Coronal view of a different tractographic study of the external and internal capsules. The fibers of the dorsal external capsule converge in the dorsal claustrum, the presumed site of the gray matter and nerve cells giving rise to the fibers. The inset shows the color-coded DTI axial map used for the selection of the correspondent ROIs (orange) at the level of the external and internal capsules. D, Fiber dissection of the left hemisphere. The dorsal external capsule has been partially removed to expose the relationship between the dorsal claustrum and external capsule, the putamen, and the corona radiata. The internal capsule is situated deep to the putamen. The superior longitudinal fasciculus is situated above the external capsule and lateral to the corona radiata. The optic radiations, which form part of the sagittal stratum, have been exposed in the sublenticular and retrolenticular portion of the internal capsule. A small window has been opened in the sagittal stratum to expose the lateral ventricle at the level of the confluence between the temporal horn and atrium. The choroid plexus has been removed to expose the posterior part of the body of hippocampus in the floor of the ventricle, and the tail of the caudate nucleus in the roof. The inferior longitudinal fasciculus, which runs from the anterobasal temporal region to the occipital lobe, has been exposed deep to the inferotemporal and temporo-occipital gyrus. The uncinate fasciculus has been cut at the level of the anterior margin of the amygdala. E, Left sagittal view of the tractrographic study shown in A. Anatomicoradiological correlation with D. Tractography permits the visualization of the internal and external capsules, at different depths. (Images courtesy of E de Oliveira)