Fig 5.

Selected images illustrating the pallidothalamic tracts. Sagittal, oblique axial (the dashed line in A represents the oblique imaging plane for B), and coronal images illustrating the complex 3D shapes and spatial relationships of the ansa lenticularis (5), lenticular fasciculus (58), and thalamic fasciculus (27). B, The ansa lenticularis originates from the inferomedial globus pallidus internus (17) and joins the lenticular fasciculus (H2 field of Forel) in the very hypointense prerubral H Fields of Forel (78). These pallidal efferents then ascend as the thalamic fasciculus (H1 Fields of Forel) to the ventral thalamus. The zona incerta (asterisk) is the bright signal intensity region in between lenticular and thalamic fasciculi in B and C. The subthalamic nucleus (6) can be seen in relationship to these structures in A. Note the dark structure just inferior to the 44 label and the dashed line is a thalamic perforating vessel.