Histochemical and immunocytochemical compartments of the thalamic VPM nucleus in monkeys and their relationship to the representational map

Abstract

The ventral posteromedial nucleus (VPM) of the monkey thalamus was investigated with correlative anatomical and physiological techniques. On the basis of staining for cytochrome oxidase (CO), VPM is divided into a lightly stained, background matrix domain and an intensely stained rod domain. The latter consists of elongated rods of large, medium, and small cells, 500 microns wide on average and extending anteroposteriorly, many of them through the full extent of the nucleus. The matrix, consisting of small cells, penetrates between the rods and expands at the dorsomedial, ventrolateral, and posterior aspects of VPM. Multiunit mapping reveals that VPM contains a dorsally situated representation of the contralateral side of the head, face, eye, and interior of the mouth and a medially situated representation of the ipsilateral side of the lips and interior of the mouth, and that the same small region is represented in the same relative position through the full anteroposterior extent of the nucleus. Earlier work had shown that single CO rods contain the representation of the same portion of the periphery throughout their length. The present study suggests that rods in equivalent positions may represent the same portion of the periphery from animal to animal. The cells of the rod and matrix domains show different patterns of immunoreactivity. Virtually all of the large- and medium-sized rod cells are immunoreactive for the calcium-binding protein parvalbumin, and many are stained by the monoclonal antibody CAT 301. Small GABA-immunoreactive cells and terminal-like puncta are highly concentrated in the rods but are dispersed in the matrix. In the matrix, all non-GABA cells are small, immunoreactive for 28-kDa calbindin, and not stained by CAT 301. They appear to form part of a wider system of calbindin-positive cells that extends into adjacent nuclei. The CO rods are indicative of the modularity of the lemniscal component of the trigeminal part of the somatic sensory system at thalamic levels. Thalamocortical relay neurons in this compartment of VPM express a calcium-binding protein and a surface proteoglycan that distinguishes them from relay neurons in the matrix compartment of the nucleus. In the following paper (Rausell and Jones, 1991), the rod and matrix compartments are shown also to have different patterns of input and output connections.

Calcium binding proteins distinguish large and small cells of the ventral posterior and lateral geniculate nuclei of the prosimian galago and the tree shrew (Tupaia belangeri).

“…Thus, the small cells in VP are not targets of the lemniscal path (11,12), and the small cell layers of GL in galago (layers 4 and 5) receive small fibers from the superior colliculus (SC), which, in turn, is the target of the smallest fibers of the optic tract (3,13). The general principle we seek may simply be that pathways to the superficial layers Abbreviations: GL, lateral geniculate nucleus; Lat, lateral nuclear group; Po, posterior nuclear group; Pul, pulvinar nucleus; SC, superior colliculus; VP, ventral posterior nucleus; VPi, inferior division of the VP; VPs, superior division of the VP.…”

“…In the past few years, Jones and his colleagues (11,12,14) have shown that large and small cells in the thalamus differ in their staining for calcium binding proteins, calbindin and parvalbumin. The clusters of big cells in VP of the monkey are rich in parvalbumin, whereas the small, pale cells in the matrix are rich in calbindin.…”

Application of Bicuculline to the Gerbil Somatosensory Cortex Induces Repetitive Ear Movements Accompanied by Induction of c-Fos Immunoreactivity in the Thalamus.

“…sensory information from the moving ear. The VL, which showed c-Fos-IR in gerbil #2, is reported to have some connection with the SI, at least in the primate [18], and might also be activated by cells in the SI. The connection between the BMI-application area of the SI and DLG is not known.…”

Neuronal responses to tactile stimuli and tactile sensations evoked by microstimulation in the human thalamic principal somatic sensory nucleus (ventral caudal)

“…In healthy animals, neural elements of the lemniscal somatosensory pathway from the spinal cord (e.g., spinocervical tract; Willis and Coggeshall 2004) to the brain stem (e.g., dorsal column nuclei) and thalamus have different staining properties from those of the spinothalamic pathway. Elements in the lemniscal pathway immunostain for the calcium-binding protein parvalbumin, whereas those in the spinothalamic pathway stain for 28-kDa calbindin (Rausell and Jones 1991b;Rausell et al 1991Rausell et al , 1992a.…”

“…For example, a skin locus such as the tip of a single finger has been stimulated at different frequencies while a monkey carries out a frequency discrimination task (Recanzone et al 1992). This task produced changes in the representation of the hand in S1 cortex, whereas a similar result was found in human S1 cortex, as mapped by high-resolution electroencephalography (Braun et al 2000).…”