Giant synapses between layer 5B (L5B) neurons of somatosensory (barrel) cortex and neurons of the Posteromedial nucleus (POm) of thalamus reside in a key position of the cortico-thalamo-cortical (CTC) loop, yet their synaptic properties and contribution to CTC information processing remain poorly understood. 
In contrast to the restricted receptive field (RF) properties of the ventral Posteromedial nucleus (VPM), neurons of the ventral thalamus zona incerta (ZI) have been shown to exhibit multiwhisker responses that vary from the ventral (ZIv) to the dorsal (ZId) subdivision.
Sensory information originating in individual whisker follicles ascends through focused projections to the brainstem, then to the ventral Posteromedial nucleus (VPM) of the thalamus, and finally into barrels of the primary somatosensory cortex (S1).
In the rodent whisker system, lemniscal and paralemniscal thalamocortical projections, from the ventral Posteromedial nucleus (VPM) and posterior medial nucleus (POm) respectively, carry distinct types of sensory information to cortex.
The involvement of these synaptic receptors in the suppressive effects of the prototypic volatile anesthetic isoflurane was assessed by local iontophoretic administration of receptor agonists/antagonists during extracellular recordings of TCNs of the ventral Posteromedial nucleus responding to whisker vibration in rats anesthetized with isoflurane concentrations of approximately 0.9 vol.% (baseline) and approximately 1.9 vol.% (ISO high).
Lesions responsible for thalamic pain are often thought to involve the ventral Posteromedial nucleus and ventral posterolateral nucleus of the thalamus.
Thus, we found immunoreactive fibers in the midline, in nuclei close to the midline (dorsomedial nucleus, centrum medianum/parafascicular complex), in the ventral region of the thalamus (ventral posteroinferior nucleus, ventral Posteromedial nucleus), in the ventrolateral thalamus (medial geniculate nucleus, lateral geniculate nucleus, inferior pulvinar nucleus) and in the dorsolateral thalamus (lateral posterior nucleus, pulvinar nucleus).
In the basal ganglia, activation in the left thalamus (ventral Posteromedial nucleus) and putamen was found.
In this study, we investigate stimulus-dependent synchronous activity in the thalamic ventral Posteromedial nucleus (VPm) using the more direct approach of local field potential (LFP) recording.
Nociceptive neurones responding to noxious stimulation of the face and oral structures were recorded in the ventral Posteromedial nucleus, posterior group and zona incerta. The percent inhibitory effects on the nociceptive neurones of each area were 68.0+/-14.8% (n = 6) in the ventral Posteromedial nucleus, 72.8+/-12.4% (n = 4) in the posterior group and 61.5+/-7.5% (n = 4) in the zona incerta.
METHODS: TCNs (n = 15) of the thalamic ventral Posteromedial nucleus responding to mechanical stimulation of whiskers were investigated in rats anaesthetized with end-tidal concentrations of isoflurane of approximately 0.9% (ISOlow, baseline) and approximately 1.9% (ISOhigh).
Two- and three-month-old CFY albino rats were sacrificied on days 1, 4, 6, 14 and 21 following operation and PSA-NCAM immunoreaction was examined at three levels of the vibrissa-cortex neuraxis, namely, in the principal nucleus of the trigeminal nerve, in the ventral Posteromedial nucleus of the thalamus and in the somatosensory cortex.
Recently, CRH mRNA has been identified in two regions of the thalamus: the posterior nuclear group (Po), and a region located at the interface of the central medial and ventral Posteromedial nucleus (parvicellular part) (CM-VPMpc).
In situ hybridization revealed neurons containing corticotropin-releasing hormone messenger RNA in the posterior thalamic nuclear group and the central medial nucleus of the thalamus, which interfaces with the ventral Posteromedial nucleus (parvicellular part). While no changes occurred in the thalamus immediately after restraint, 3 h after restraint, increases in corticotropin-releasing hormone messenger RNA occurred in both the posterior thalamic nuclear group and the central medial-ventral Posteromedial nucleus (parvicellular part) of the thalamus.
Here we focus on the two major trigeminal nuclei of the brain stem, nucleus principalis and subnucleus interpolaris, and on their thalamic targets, the ventral Posteromedial nucleus (VPM) and the medial division of the posterior nucleus (POm).
Local iontophoretic administration of the gamma-aminobutyric acid-A (GABA(A)) receptor antagonist bicuculline in the thalamic ventral Posteromedial nucleus reversed suppressive effects of isoflurane on thalamocortical relay neurons (TCNs).
Here, the authors investigated the size gradients of the barreloids in the ventral Posteromedial nucleus of the rat thalamus. The largest barreloids in the ventral Posteromedial nucleus were those that represent whiskers C2-C4, D2-D4, and E2-E4, which are neither the largest nor the most innervated whiskers in the mystacial pad.
As previously reported, the ventral Posteromedial nucleus (VPM) of rats showed dense AChE staining from P-0 at least through P-8.
In the ventral Posteromedial nucleus of the thalamus (VPM) of partly denervated animals, however, only minutes or hours after the nerve crush, certain units were found to respond in some cases not only to the vibrissae, but also to mechanical stimulation of the face over the eye (two units), the nose (one unit), and the midline (one unit).
The labeling of small groups of trigeminothalamic axons with biotinylated dextran amine disclosed two broad classes of axons; a majority of fibers (68%; n = 107) project to a single barreloid of the ventral Posteromedial nucleus, and the remaining group includes axons that innervate both the posterior group of the thalamus and the tectum. Additional terminal sites for axons of this latter group may include the pretectum, the zona incerta, the medial part of the medial geniculate nucleus, and the ventral Posteromedial nucleus. Solid retrograde labeling of cells that project to the ventral Posteromedial nucleus and intracellular staining revealed that single-whisker cells have small somata and narrow, barrelette-bounded dendritic trees.
Single-unit recordings of thalamo-cortical relay neurons (TCNs, third order neurons; n=28) and presumed trigemino-thalamic fibers (TTFs, second order neurons; n=7) were performed in the ventral Posteromedial nucleus.
Corticothalamic cells (46%) are small, short pyramids projecting either to the ventral Posteromedial nucleus alone or to the posterior group as well.
The second most effective lesion was in the medial thalamus including the parvocellular part of the ventral Posteromedial nucleus of the thalamus (VPMpc) and the midline part, followed by the damage of the lateral nuclear group of the amygdala including the basolateral amygdaloid nucleus.
Injection of FG into the ventral Posteromedial nucleus of the thalamus resulted in labeling of scattered neurons contralaterally in the TNC.
Neurons from different parts of the VB were investigated: 29 units were located medially, in the ventral Posteromedial nucleus (VPM; facial RFs), and 11 units were located laterally, in the ventral posterolateral nucleus (VPL; forepaw and body RFs).
We also analyzed the effect of neonatal ION transection on the soma-dendritic morphology of individual neurons in the ventral Posteromedial nucleus of the thalamus (VPM) by intracellular injection of horseradish peroxidase (HRP) in vivo and Lucifer yellow in fixed slices.
We wished to determine whether (i) the inhibition observed in the VPL was operating at the thalamic level, (ii) was dependent on GABA receptors, (iii) was demonstrable on neurons of the ventro-Posteromedial nucleus of the thalamus (VPM) and (iv) was operant on test responses evoked by natural stimuli.
Intake and taste reactivity tests were used to determine the effects of bilateral lesions of the gustatory portions of the nucleus of the solitary tract (NST), the parabrachial nucleus (PBN), and the ventral Posteromedial nucleus of the thalamus (VPMpc) on several complex ingestive behaviors.
Responses of the thalamic non-specific medial nuclei and relay ventral Posteromedial nucleus neurons evoked by stimulation of the teeth pulp of A alpha and A sigma fibers of infraorbital nerve and caudal nucleus of the spinal trigeminal tract were studied in cats under thiopental-chloralose anesthesia. In the ventral Posteromedial nucleus 47% of neurons formed the low-threshold group, 4% made up the high-threshold group and 49% were convergent. Ninety per cent of the medial nuclei neurons and 79% of the ventral Posteromedial nucleus neurons responded to stimulation of the caudal nucleus spinal trigeminal tract. In the ventral Posteromedial nucleus 40% of responses induced by stimulation of teeth pulp and A sigma fibers of the infraorbital nerve were completely suppressed and 26.4% of responses induced by stimulation of the A alpha fibers of the infraorbital nerve were completely suppressed. Conditioning stimulation of the central gray matter suppressed responses evoked by stimulation of the caudal nucleus spinal trigeminal tract and in the most part neurons of the medial nuclei and neuron responses of the ventral Posteromedial nucleus.
The ventral Posteromedial nucleus (VPM) of the monkey thalamus was investigated with correlative anatomical and physiological techniques.
The ventral Posteromedial nucleus (VPM) of the monkey thalamus was investigated with combined immunocytochemical, histochemical, and connection-tracing techniques.
Jaw movements during chewing were also analyzed in the animals with either bilateral ablation of the cortical masticatory area (CMA) or bilateral lesion of the ventral Posteromedial nucleus (VPM) of the thalamus in order to examine whether profound effects of trigeminal deafferentation are produced via the transcortical loop.
Whisker-sensitive thalamic neurons were confined to the ventral Posteromedial nucleus (VPM).
SP fibers are particularly concentrated in the ventral Posteromedial nucleus.
Within the VB complex all LT units in the ventral Posteromedial nucleus had receptive fields on the head; most ventral posterolateral nucleus LT units had receptive fields on the body.
Cytochrome oxidase (CO) histochemistry was used to examine patterns of metabolic activity in the ventral Posteromedial nucleus of the adult rat thalamus.
On the BLAC there are massive projections of: a) nuclei of the middle line of the precommissural pole of the dorsal thalamus (anterior parts of the paratenial, interanteromedial and reunial nuclei), as well as the whole anterior paraventricular nucleus, medial part of the ventral Posteromedial nucleus; b) postcommissural nuclei of the dorsal thalamus; some "nonacustical" nuclei of the internal geniculate body (ventrolateral nucleus, medial and macrocellular parts and the most caudal end of the internal geniculate body).
Several corroborative lines of evidence indicated that tooth pulp-evoked FFPs and ENFPs originate from the following generator sources: I, inferior alveolar (dental) nerve/semilunar (gasserian) ganglion; IIa,b, trigeminal lemniscal fibers from the principal (main) sensory nucleus; IIIa,b, thalamocortical fibers from the thalamic ventral Posteromedial nucleus; P1, N1, cytoarchitectural area 3 on the banks of the coronal or orbital sulcus.
The neurons in VPL are aligned in rostrocaudal and dorsoventral rows that are roughly parallel to the curvature of the external medullary lamina (EML) and curve partially around the rostral pole of the ventral Posteromedial nucleus (VPM).
The activity of 34 neurons of the ventral and Posteromedial nucleus of the thalamus, a transmissive link of the gustatory analyzer, was studied in fed rabbits before and after the alimentary reaction was produced by stimulation of the lateral hypothalamus.
The Posteromedial nucleus (POm) receives a dense spinothalamic projection medially and ventromedially; elsewhere in the POm the projection is more scattered.
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