ABSTRACT
The cerebellothalamic tract [or fasciculus cerebellothalamicus ( fct)] is represented in the maps in Chapters 3 and 4, and in relation to the myeloarchitecture in sagittal and horizontal sections of Figures 5.1 and 5.2. It corresponds in large part to Hassler’s prelemniscal radiations (“ra.prl”) (26) and to the prerubral field or field H of Forel (56,111). The trajectory of the tract analysed in the three stereotactic planes is toward the posterior part of the ventral medial (VM) nucleus and the ventral lateral posterior nucleus (VLp), with possible extension into the VLa (e.g., Fig. 5.1). In some sections, part of the tract appears to take a posterior course toward the intralaminar nuclei. This would confirm an observation made in monkeys where cerebellar fibers taking a posterior course reach the CL nucleus (33). The tract is characterized by enhanced parvalbumin immunoreactivity, like the VLp and the RN (Figs. 3.26 and 3.27). The bulk of the fct is posterior and lateral to the pallidothalamic tract, and they come close together at some levels (Fig. 5.1), although still separated as reported earlier (112). The work by Nauta and Mehler (94) on striatal and pallidal connections in the monkey also gives an “historical” review on the early descriptions of the pallidothalamic pathways. From his early work (111), the fields bearing Forel name (H, H1, and H2) have been used to describe pallidothalamic fibers, though only H2 and H1 were later recognized to originate from the pallidum through the ansa and fasciculus lenticularis (al and fl, respectively). They were first noted by C. Vogt (113) to merge as H1 + H2 to form the fasciculus thalamicus ( ft).
