Thalamic terminal fields of individual axons from the ventral part of the dentate nucleus of the cerebellum inMacaca mulatta

Abstract

This study examined organization of the projection from the dentate nucleus of the cerebellum to the ventral lateral nucleus (VL) of the thalamus in Macaca mulatta. Small injections of biotinylated dextran amine were placed in the ventral parts of dentate nuclei. The distribution of all contralateral terminal fields in the thalamus was charted, and representative individual axons that terminated in the VL were traced in serial sections under the light microscope. These axons were reconstructed with all their branches and terminal fields in the thalamus. The geometry and size of the terminal fields as well as the number and distribution of boutons and neurons in them were analyzed. The terminal fields of all labeled axons were distributed widely over the VL either singly or in clusters. Two types of axons were found: simple axons formed only one terminal field and complex axons formed multiple terminal fields at a distance. Individual terminal fields were focal, had the form of flattened discs, and generated up to 200 boutons distributed between 10 and 29 nerve cell bodies. These findings suggest that a simple axon activates a small group of neurons at one site. The complex axons, in turn, influence similar size cell groups at different VL locations. The total number of boutons generated by a single complex axon was up to 300. Future studies should determine whether simple axons could be branches of complex axons that took off below the thalamus. The results reveal a complex organization of the input from the ventral dentate to the VL that only partially fits into the traditional concept of somatotopic organization of the nucleus. J. Comp. Neurol. 421:412–428, 2000. © 2000 Wiley‐Liss, Inc.

Nuclei-specific thalamic connectivity predicts seizure frequency in drug-resistant medial temporal lobe epilepsy

“…With respect to the motor and sensory relay nuclei, epileptic patients showed increased RSFC for the seed masks of left and right parvocellular ventral lateral nucleus (VLpv), and anterior ventral lateral nucleus (VLa), as well as the VPLp and VPLa, and decreased RSFC for seed masks of left magnocellular lateral geniculate nucleus (LGNmc), and right medial geniculate nucleus (MGN). The VL group had strong cortical connectivity to the primary motor cortex, superior and middle frontal gyri and frontal pole, and subcortically to the striatum and brainstem (Mason et al, 2000). The gradient of connectivity was aligned along an anterior-rostral to posterior-caudal axis.…”

Review: management of Parkinson's disease

“…Possible side effects of this target are on the one hand a stimulation of structures in the vicinity of the VLp with resulting dysarthria, paresthesias, or gait disturbances and on the other hand mild executive deficits (eg, in verbal fluency) 126. Therefore exact planning and meticulous intraoperative testing of tremor-dominant and elderly patients is required in order to stimulate segregated motor loops 4,127…”

Human Motor Thalamus Reconstructed in 3D from Continuous Sagittal Sections with Identified Subcortical Afferent Territories

“…It is known from experimental studies in animals that fibers from medial globus pallidus, substantia nigra pars reticularis, and deep cerebellar nuclei reach also some other thalamic nuclei besides VAp, VAn, and VL. For example, there is some nigral and cerebellar input to MD ( Ilinsky et al, 1985 ; Mason et al, 2000 ), but these projections are patchy and scanty, hence not easily identifiable in the human thalamus. Cerebellar output also reaches CL, but as pointed out above, its boundaries were indistinct in our material.…”

“…DTI reveals mainly the fiber bundles whereas anatomic pathway tracing and specific immunostaining patterns expose the terminal zones. Besides, both cortical and subcortical fiber bundles on entering thalamus break up to individual fibers that take sometimes very tortuous course before reaching their final destinations (see for example individual cerebellothalamic fibers in Mason et al, 2000 ; and corticothalamic fibers in Kultas-Ilinsky et al, 2003 ). The exception are the prefrontal cortex fibers running in the anterior limb of internal capsule that stay within the bundles for some distance in the thalamus specifically when passing through VA, i.e., the basal ganglia afferent zone, en route to MD.…”