Retrograde analyses of spinothalamic projections in the macaque monkey: Input to the ventral lateral nucleus

Abstract

The distribution of retrogradely labeled spinothalamic tract (STT) neurons was analyzed in monkeys following variously sized injections of cholera toxin subunit B (CTb) in order to determine whether different STT termination sites receive input from different sets of STT cells. This report focuses on STT input to the ventral lateral nucleus (VL), where prior anterograde tracing studies identified dense or moderately dense STT terminations. Large and very large injections in VL produced large numbers of labeled cells predominantly in laminae V and VII (more than half as many as from massive injections in the entire thalamus). Medium-sized and small injections in VL labeled STT cells almost exclusively in laminae V and VII, in segments consistent with the coarse mediolateral VL topography; few or no cells were labeled in lamina I. All injections labeled the deep cerebellar nuclei (see accompanying article: Evrard and Craig, 2008). Notably, even the most anterior injection in VL that produced dense pallidal labeling still labeled both STT and deep cerebellar cells. These observations indicate that VL receives STT input originating from laminae V and VII neurons that may be coextensive with its cerebellothalamic input. These findings support the role of laminae V and VII STT cells in sensorimotor integration and suggest a significant ongoing influence on both motor and premotor thalamocortical function. Together with the preceding observations of selective STT projections to other thalamic regions, these results provide compelling evidence that the primate STT consists of anatomically and functionally differentiable components.

Glutamic acid decarboxylase isoform 65 immunoreactivity in the motor thalamus of humans and monkeys: γ‐aminobutyric acidergic connections and nuclear delineations

“…Although at this point a consensus has been reached that Vim is the recipient of cerebellar input, the argument among investigators who probe the human thalamus during stereotactic interventions (Ohye et al, 1989;Lenz et al, 1990) has been focused on whether it also receives a direct overlapping spinothalamic input or whether the latter is confined only to the somatosensory territory posterior to the cerebellar afferent zone. Both neurophysiological and neuronatomical animal studies, and especially the most recent ones, are coming to agreement that there is an overlap of the direct spinothalamic and cerebellothalamic afferents in VL and especially in its ventral part (for review see Craig, 2008). In view of the existing evidence and the overall similarity between monkeys and humans regarding the topographic relationships of the territories of subcortical afferents in the thalamus, this can be extrapolated to the human thalamus with a high degree of confidence.…”

“…In rhesus monkey, in the nomenclature of the atlas by Ilinsky et al (2002a), most cerebellothalamic fibers terminate in the ventral lateral (VL) and the centrolateral (CL) nuclei, both of them also receiving direct spinothalamic input; the major recipients of pallidothalamic fibers are the pars densicellularis and pars parvicellularis of the ventral anterior nucleus (VApc/VAdc) and the centromedian nucleus (CM); nigrothalamic fibers terminate in the pars magnocellularis of the ventral anterior nucleus (VAmc; for review see Asanuma et al, 1983;Kultas-Ilinsky, 1987, 2002b;Mackel et al, 1992;Sakai et al, 1996;Mackel, 2001;Stepniewska et al, 2003;Craig, 2008;Evrard and Craig, 2008). Moreover, with these subcortical inputs as criteria, the medial dorsal nucleus (MD) can also be considered a member of this nuclear group, because its two subdivisions, MDmf (pars multiformis) and MDmc (pars magnocelularis), receive an input from the substantia nigra , whereas the two others, pars parvicellularis (MDpc) and pars densicellularis (MDdc), receive cerebellar input (Middleton and Strick, 1997;Mason et al, 2000).…”

Termination Zones of Functionally Characterized Spinothalamic Tract Neurons Within the Primate Posterior Thalamus

“…The mean conduction velocity of marginal zone and deeper cells was 28.0 Ϯ 11.6 and 34.2 Ϯ 7.4 m/s, respectively. Previous studies have shown a small projection of the STT to ventral lateral (VL) nucleus in cats (Jones and Burton 1974) and primates (Boivie 1979;Craig 2008). In this study, we did not surround the rostral end of axons that were antidromically activated in VPL.…”

Cross-modal plasticity in the human thalamus: evidence from intraoperative macrostimulations

“…2a and b) suggests no prevailing fixed modality but a dominant TCD-related plastic phenomenon in the two patient groups examined. The presence of dominant somatosensory responses in NP patients is particularly striking because these nuclei receive little, if any, peripheral input (Stepniewska et al 2003;Craig 2008) and project dominantly to premotor and supplementary motor cortex (Matelli and Lupino 1996;Rouiller et al 1999;Morel et al 2005). Some factors could lead to a "misplacement" of the electrode more posteriorly and laterally into VLp or VPL, which receive somatosensory inputs.…”