Comparison of cerebellothalamic and pallidothalamic projections in the monkey (Macaca fuscata): A double anterograde labeling study

Abstract

To address the question of segregated projections from the internal segment of the globus pallidus (GPi) and the cerebellar nuclei (Cb) to the thalamus in the monkey, we employed a double anterograde labeling strategy combining the anterograde transport of horseradish peroxidase conjugated to wheat germ agglutinin (WGA-HRP) with biotinylated dextran amine (BDA) transport. The tissue was processed sequentially for WGA-HRP, and then BDA immunohistochemistry using two different chromogens. Since the two labels were easily distinguishable on the same histological section, the interrelationship between the cerebellar and pallidal projection systems could be directly evaluated. We found that both the cerebellothalamic and pallidothalamic label consisted of dense plexuses of labeled fibers and swellings in a patch-like configuration. The patches or foci of labeling were distributed either as dense single label or as interdigitating patches of double label. We found dense single label in the central portion of the ventral anterior nucleus pars principalis (VApc) and the ventral lateral nucleus pars oralis (VLo) following the GPi injections or in the central portion of the ventral posterior lateral nucleus pars oralis (VPLo) and nucleus X (X) following the cerebellar nuclei injections. Complementary interdigitating patches of WGA-HRP and BDA labeling were found primarily in transitional border regions between thalamic nuclei. On occasion, we found overlap of both labels. We observed a gradient pattern in the density of the pallidothalamic and cerebellothalamic projections. The pallidothalamic territory included VApc, VLo, and the ventral lateral nucleus pars caudalis (VLc), with the density of these projections decreasing along an anterior to posterior gradient in the thalamus. Occasional patches of pallidal label were found in VPLo and nucleus X. Conversely, the density of cerebellothalamic projections increased along the same gradient, with the cerebellothalamic territory extending anteriorly beyond the cell-sparse zones of VPLo, X, and VLc to include VLo and VApc also. These data suggest that although the cerebellar and pallidal projections primarily occupy separate thalamic territories, individual thalamic nuclei receive differentially weighted inputs from these sources.

Vestibular Signals in Primate Thalamus: Properties and Origins

“…Furthermore, thalamic projections from these nuclei primarily terminate in VL (Fig. 12) (Stanton, 1980;Asanuma et al, 1983;Thach, 1987;Sakai et al, 1996;Middleton and Strick, 1997). Finally, retrograde labeling of CN neurons after an injection into a vestibular responsive region of dorsal VL supports this alternative pathway (Figs.…”

“…Furthermore, neuroanatomical studies have clearly shown cerebellar nuclei (CN) projections to the thalamus, particularly to the VL (Stanton, 1980;Asanuma et al, 1983;Thach, 1987;Sakai et al, 1996;Middleton and Strick, 1997). Consequently, cerebellothalamic projections may provide an additional route for vestibular information to the thalamus.…”

Unravelling cerebellar pathways with high temporal precision targeting motor and extensive sensory and parietal networks

“…As mentioned earlier, previous work based on conventional anatomical tracing techniques has suggested that the numerically major output of the DCN is destined to specifi c contralateral thalamic subnuclei VPLo, X (Nucleus X of the thalamus) and VLc, which in turn project to the motor cortex 12 . In addition, a numerically less prominent projection to the contralateral intralaminar nucleus has been delineated 15,16 . Hence, one scenario able to explain our discovery of multiple regions of activation within the contralateral cerebro-cortical hemisphere is that there are additional pathways involving other thalamic nuclei such as the intralaminar nuclei.…”

Distinct Contribution of the Striatum and Cerebellum to Motor Learning

“…In the motor domain, for example, authors have often noted that basal ganglionic deficits are seen during attempts to relax and rest, whereas cerebellar dysfunctions are only seen during movements. Not surprisingly, such a distinct profile of cognitive and motor deficits has been supported by neuroanatomical findings which have shown that the cortico-basal ganglia-thalamo-cortical and the cortico-cerebellothalamo-cortical loops constitute two separate neural systems (Asunama, Thach, & Jones, 1983;Middleton & Strick, 1994;Percheron, François, Yelnik, Fénelon, & Talbi, 1993;Sakai, Inase, & Tanji, 1996;Yamamoto, Yoshida, Yoshikawa, Kishi-moto, & Oka, 1992). They have also been corroborated by imaging studies which have shown a distinct involvement of these structures in the control of movement (see Jueptner & Weiller, 1998, for a review).…”