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PubMed1986

Extent of the ipsilateral representation in the ventral posterior medial nucleus of the monkey thalamus.

Single and multiunit mapping was used to determine the extent of the representation of ipsilateral structures in the ventral posterior medial (VPM) nucleus of the thalamus in cynomolgus monkeys. The extent of the VPM occupied by terminations of afferent fibers arising in the ipsilateral principal trigeminal nucleus was also determined by anterograde transport of horseradish peroxidase. Both methods indicate that most of the medial half of VPM is occupied by the ipsilateral representation. This is much larger than previously suspected. Units in the medial half of VPM have small, well localized receptive fields on the ipsilateral side of the lower lip, tongue and palate, in the ipsilateral cheek pouch and on the ipsilateral teeth. The representation is largest for the ipsilateral side of the tongue and the cheek pouch. Most units in the lateral half of VPM have small, contralateral receptive fields. Few units in VPM have bilateral receptive fields. VPM is clearly distinguishable by cytochrome oxidase (CO) staining. Anteroposteriorly elongated, CO-positive aggregations correspond to elongated aggregations of units with the same or closely similar receptive fields, especially in the medial, ipsilateral representation.

Animals↗
PubMed1977

Vestibular responses in the rhesus monkey ventroposterior thalamus. II. Vestibulo-proprioceptive convergence at thalamic neurons.

The vestibular thalamic relay in the Rhesus ventrobasal complex, identified in a previous field potential study (part I, Deecke et al., 1974), has now been investigated with neuronal recordings in the thalamus in order to clarify its functional role. In part I, short latency responses (2.5 msec) were found in the corner between VPL, VPM and VPI nuclei, largely including dorsal portions of the VPI nucleus. Field potentials of somewhat longer latency (4-5 msec) were recorded in VPL and in other thalamic nuclei, including the posterior nuclear group. Neuronal responses were recorded in thalamic nuclei of awake flaxedilized Rhesus monkeys. Cells not responding to vestibular stimulation (round window polarisation of either labyrinth) were ignored. The great majority (80%) of those neurons responding to labyrinth polarisation showed convergence with deep somatic (proprioceptive) input from joints and muscles of vertebral column and limbs. 60% of these bimodal neurons responded to movement of cervical joints. Very few vestibularly responsive cells received cutaneous (6.6%), non-optokinetic visual or auditory (2.6% each) input. Proprioceptive fields tended to be large, frequently involving more than one joint, and could be even bilateral. For a few cells the pattern of vestibulo-proprioceptive convergence could be fitted to a coordinated body position that might occur during normal locomotion. 78% of the cells responded to polarisation of both labyrinths, indicating strong bilateral projection.

Animals↗
PubMed1986

Localized responses in the midsuprasylvian gyrus of the cat following stimulation of the central lateral nucleus in thalamus.

Evoked responses were mapped in the cerebral cortex following low intensity electrical stimulation in serial penetrations of the medial and intralaminar nuclei of the thalamus of the cat. A projection was found from one of the intralaminar nuclei, the central lateral nucleus (CL) to the midsuprasylvian gyrus, mainly areas 5 and 7. The projection is suggested to be direct, since the evoked responses had a short latency initial positivity. The most characteristic type of response consisted of this early positivity followed by two successive negativities. The earlier, so called first negativity followed high frequency stimulation and was recorded in a smaller area of the cortex than the later, so called second negativity. The first negativity is suggested to depend on monosynaptic depolarization and activation of cortical cells. The second negativity failed at frequencies higher than 10 Hz and was strongly depressed by the administration of barbiturates; it is suggested to depend on polysynaptic depolarization and cellular activity. In electrode penetrations of the cortex both negativities reversed at the border between cortical layers II and III, indicating a superficial termination of thalamic afferents in the cortex. The cortical evoked response to CL stimulation was facilitated by light mechanical and low intensity electrical stimulation of the periphery, as well as by electrical stimulation of the tooth pulp. The possible significance and function of this projection is discussed in relation to arousal, attention and pain.

Animals↗
PubMed1985

The cholinergic innervation of the visual thalamus: an EM immunocytochemical study.

In this study we demonstrate at the ultrastructural level that both the dorsal lateral geniculate nucleus (dLGN), the visual relay of the thalamus, and the perigeniculate nucleus (PGN), the visual segment of the thalamic reticular nucleus (TRN), are densely innervated by fibres with Choline-Acetyl-Transferase (ChAT) like immunoreactivity. These axons make synaptic contacts with interneurones considered to be inhibitory, both in the PGN and within the synaptic glomeruli of the dLGN. In addition, Chat positive terminals form intra- and extraglomerular synapses with dendrites thought to arise from relay cells. We interpret these results as evidence for direct cholinergic modulation of both relay cells and inhibitory interneurones.

Animals↗
PubMed1986

Projection of tooth pulp afferents to the thalamus of the cat. II. Distribution and characteristics of single units.

Single unit activity was recorded extra- and intracellularly in the thalamus of the cat following electrical stimulation of tooth pulp afferents. Cells activated by noxious stimuli were found in the basal ventromedial nucleus (VMB), the marginal zones of the arcuate and external nuclei of the ventrobasal complex (VBA and VBX) and the intralaminar complex. Cells found in any of these locations showed a variety of properties; they were activated at different latencies and had different patterns of input. However, cells with responses of short latency and low convergence were with few exceptions found in or close to VMB. Stimulation of tooth pulp evoked both EPSP's and IPSP's in these cells. A subpopulation of cells were found that responded to stimulation of either right or left tooth pulp afferents. 22 units, mainly located in VMB, were found that responded exclusively to stimulation of tooth pulp afferents. In the laterodorsal part of VMB cells influenced by tooth pulp stimulation were found to be antidromically activated by stimulation of the cortical tooth pulp projection area. No such cells were seen at other locations. The results of this study is in agreement with the conclusions in the companion paper (Rydenhag et al. 1986a) that VMB and the border zone between VMB and VBA are the most likely relay nuclei between tooth pulp nociceptive afferents and the cortex. The intralaminar complex is suggested to be important in the cortical arousal reactions and direction of attention following a painful stimulus.

Afferent Pathways↗
PubMed1979

Vestibular, auditory, and somatic input to the posterior thalamus of the cat.

The responses of 157 neural units in the magnocellular (mc) and parvocellular (pc) components of the medial geniculate nucleus (MG) and other nuclei of the posterior (PO) thalamic group were recorded and analyzed. Units were tested for a response to electrical stimulation of the vestibular nerve, natural auditory and electrical cochlear nerve stimulation, and natural stimulation of joint, muscle, and cutaneous receptors of the limbs, trunk, and neck (somatic stimulation). Only 45% of the units responded to these stimuli. Twenty-four percent of the responsive units were multimodal, responding to more than one stimulus. All multimodal units were activated by auditory stimuli. More units responding to vestibular stimulation were found in mcMG than in pcMG or other components of the PO group. Potentials evoked by vestibular nerve stimulation were recorded in all 3 regions with latencies of 5--25 msec. No evidence was found for a thalamic relay from vestibular nerve to cortex in the area investigated, since the recorded latency for activity from vestibular nerve stimulation was longer than the latency of responses recorded in the cortex. This region of the thalamus appears to be important for reception of auditory information and integration with vestibular and somatic modalities.

Acoustic Stimulation↗
PubMed1979

The afferents and projections of the ventroposterolateral thalamus in the monkey.

In seven monkeys (M. fascicularis), recordings were made from neurones in subnuclei VPLo and VPLc of the thalamus. The peripheral inputs to these cells from the forelimb were established by stimulating muscle, skin and joint nerves, and cutaneous receptive fields were examined by natural stimulation of the skin. The projection of the same cells to motor and sensory cortex was examined by stimulation of the cortex to demonstrate antidromic responses and by retrograde axonal transport of horseradish peroxidase injected into these regions of cortex. Of the 139 neurones which were driven by stimulation of peripheral nerves, 73 were located in VPLo. This suggests that there is a significant projection of forelimb afferents to VPLo in the monkey. Of the 73 neurones located in VPLo, 60 responsed to stimualtion of muscle or joint nerves. The projection to VPLo is therefore predominantly from deep receptors. Twenty-one of these 73 neurones had convergent inputs. The latencies of activation of units in VPLo were short (4--8 ms) and consistent with a lemniscal pathway via the dorsal column nuclei. Injection of horseradish peroxidase into the arm area of the motor cortex labelled cells in VPLo and not in VPLc. The neurones from which recordings were made in VPLo were located within the population of cells labelled with horseradish peroxidase after injections into the primary motor area. This suggests that this subnucleus is the thalamic relay for the sensory input from peripheral receptors to cells of the motor cortex.

Afferent Pathways↗
PubMed1987

Postnatal development of the striate cortical projection onto the extrageniculate visual thalamus in the cat: an HRP study.

The postnatal development of the striate cortical projection onto the extrageniculate visual thalamus was examined by using the orthograde and retrograde HRP methods. At birth, the projection is present, and fibres of the projection terminate in the lateral part of the lateral posterior nucleus. A rough topographical arrangement of the projection is already established. Neurones that give rise to the projection are located exclusively in layer V from birth onward. However, the neurones are much more densely packed at birth than in adult cats. The packing density of the neurones decreases rapidly during the second postnatal week, and afterwards continues to become gradually lower. In the meantime, the cross sectional area of the neurones increases sharply during the second postnatal week. These findings suggest that striate cortical neurones projecting onto the lateral posterior nucleus rapidly complete the final stages of their maturation shortly after the normal opening of the eyelids, and during this time some of these neurones undergo axonal elimination or neuronal death, or both.

Animals↗
PubMed1990

Regional differences in the distribution of endogenous receptors for carbohydrate constituents of cellular glycoconjugates, especially lectins, in cortex, hippocampus, basal ganglia and thalamus of adult human brain.

Ten different types of labelled neoglycoproteins, exposing glycohistochemically pivotal carbohydrate moieties that mostly are constituents of naturally occurring glycoconjugates with an aromatic spacer, were synthesized. The panel was applied to fixed, paraffin-embedded sections of different cortical regions and white matter, of hippocampal gyrus, basal ganglia, thalamus nuclei and adjacent areas of adult human brain to comprehensively map the presence of respective binding sites in these parts. Compliance with accepted criteria for specificity of binding was routinely ascertained. Overall, not a uniform binding pattern, but a distinct distribution with regional differences on the level of specific cytoplasmic and nuclear staining in nerve cells was determined, fiber structures being generally labelled with medium or strong intensity. For example, among the neurons localized in the five cortical laminae the binding of N-acetyl-D-galactosamine varied from strong to undetectable. Biochemical analysis, employing carbohydrate residues as affinity ligands in chromatography, proved that the neuroanatomically different regions exhibited a pattern of receptors with notable similarities. These results on endogenous binding sites for glycoconjugates, especially lectins, are complementary to assessment of localization of cellular glycoconjugates by plant lectins and carbohydrate-specific monoclonal antibodies. They are thus a further obligatory step to substantiate the physiological roles of recognitive protein-carbohydrate interactions in the central nervous system.

Adult↗
PubMed1987

Computed tomography of germinomas in basal ganglia and thalamus.

CT findings of 6 cases with germinoma originating in the basal ganglia and thalamus are reported. The early finding of germinoma in this region on plain CT, was an irregularly defined, slightly high density area without mass effect. Repeated CT scanning showed enlarging iso-density lesion accompanied by mass effect to high. Intratumoral cysts and calcifications were frequently observed. The tumor showed mild to moderate and inhomogeneous enhancement by intravenous injection of contrast medium. A tendency to ipsilateral hemicerebral atrophy was found in one case. These findings were somewhat different from those of germinomas in the pineal and suprasellar regions. This phenomenon may be related to the anatomical difference of the brain where the tumor originated.

Adolescent↗
PubMed1987

Axonal polyglucosan body in the ventral posterolateral nucleus of the human thalamus in relation to ageing.

Axonal polyglucosan bodies in myelinated axons in the ventral posterolateral nucleus of the human thalamus (VPL) are described. These axonal inclusions were distributed exclusively in the dorsolateral part of the caudal VPL, and their arrangement may be associated with fibres originating from the gracile nucleus. They were not observed in patients under age of 50, and appeared to increase in number and size with advancing age. It is suggested that axonal polyglucosan bodies are an ageing phenomenon of the secondary sensory fibres.

Adolescent↗
PubMed1992

Morphological characteristics of different types of neurons in the ventrooralis anterior, ventrooralis internus, and ventrooralis posterior nuclei in the human thalamus.

1. Golgi-Kopsch preparations of the oral ventral nuclei of human thalamus were analyzed in an attempt to classify the neuronal types. 2. Three types of neurons are described for the first time in humans. Type I neurons are large or medium in size and bear dendrites with protrusions, spines, and short hair-like appendages. Some have a radiate dendritic arbor and others have dendrites grouped in tufts. The dendritic trees of these neurons are dense. 3. Type II neurons are medium or small in size with less dense dendritic trees. These cells have somatic as well as dendritic appendages of different forms. 4. Relatively rare is a type of very small neurons, type III, with few and sparsely branching dendrites.

Adult↗
PubMedDate not supplied

Reactions of neurons of the posterior ventral nucleus of the thalamus of the rat during movements of the vibrissae.

The reactions of neurons of the posterior ventral nucleus of the thalamus were investigated during movements of the vibrissae, accomplished independently by the animal, in experiments on rats utilizing a technique of partial curarization proposed by the author. Differences were identified in the pattern of the reactions of the thalamic neurons to deviation of a vibrissa by the experimenter from the pattern of the reactions of the same neurons to deviation of the vibrissa elicited by its hitting against a barrier during a sweep. A dependence of the response of the sensory neurons on whether or not the barrier was mobile during the period of the sweep of the vibrissae was also demonstrated. The hypothesis is advanced that at the thalamic level the analysis of the parameters of the stimulus is accomplished in connection with information regarding movements of the vibrissae.

Animals↗
PubMedDate not supplied

Locus ceruleus and neuronal activity of the reticular nucleus of the thalamus.

Reactions of neurons of the reticular nucleus of the thalamus and lateral geniculate body to stimulation of the locus ceruleus were studied on their unanesthetized, immobilized cats. It was found that preliminary brief rhythmic stimulation of the locus ceruleus causes inhibition of the activity of the majority of neurons of the reticular nucleus and facilitation of relay neurons of the lateral geniculate body. Such reactions are clearly exhibited during simultaneous recording (by means of two microelectrodes) of the neuronal activity of these brain structures.

Action Potentials↗
PubMedDate not supplied

Reactions of neurons of the mediodorsal nucleus of the thalamus to the stimulation of peripheral nerves.

The reactions of neurons of the associative mediodorsal nucleus of the thalamus to a solitary stimulation of the radial, sciatic, and splanchnic nerves were studied in conditions of an acute experiment in anesthetized and immobilized cats. There were 91.85, 90.56, and 81.35% reactive neurons, respectively. They were mainly concentrated in the parvocellular division of the nucleus. A high degree of convergence (82.6%) of somatic and visceral signals was found and their interaction was of the reciprocal blocking type.

Animals↗
PubMed1985

Synaptic terminals in the ventroposterolateral nucleus of the thalamus from neurons in the dorsal column and lateral cervical nuclei: an electron microscopic study in the cat.

The afferent fibres to the ventroposterolateral nucleus (VPL) of the contralateral thalamus from neurons in the dorsal column nuclei (DCN) and the lateral cervical nucleus (LCN) were labelled by anterograde transport of wheat germ agglutinin-horseradish peroxidase conjugate and subsequent histochemical processing with tetramethyl benzidine. In accordance with the results of previous light microscopical studies using the degeneration method or autoradiographic tracing technique, the distribution of the afferents from the DCN and LCN in the VPL differed considerably. Thus the DCN terminals, which were calculated to constitute about 7-8% of the total number of boutons in the VPL, were found throughout the entire VPL, whereas the LCN terminals were mainly located in its dorsal and dorsolateral parts, where they made up about 1% of the total number of boutons. However, the morphology and synaptic organization of the terminals from the DCN and LCN were virtually identical. Thus the synaptic terminals of the two afferent pathways seemed to be represented by large boutons of a similar type, which had large, slightly oval and loosely packed synaptic vesicles and contained numerous mitochondria. Both DCN and LCN terminals synapsed preferentially on medium-sized to large dendrites, but were also presynaptic to other vesicle-containing profiles, probably of internuncial origin, which in turn were in synaptic contact with the same dendrites as the labelled ones. It is suggested that the differences in physiological properties between the somatosensory information that is transmitted to the somatosensory cortex via the dorsal column-medial lemniscus pathway and the spino-cervico-thalamic tract do not seem to have a counterpart in differences in the synaptic organization of their relay in the VPL.

Afferent Pathways↗
PubMedDate not supplied

Effect of stimulation of the reticular nucleus of the thalamus on neuronal activity of associative and nonspecific thalamic structures.

The reactions of neurons of the centromedian, mediodorsal, and posterior lateral nuclei of the thalamus to electrostimulation of its reticular nucleus were studied in experiments on anesthetized cats. A high reactivity of neurons of the centromedian (53.7%) and mediodorsal (48.3%) nuclei in comparison with the posterior lateral (10%) was established. "Silent" neurons reacted by an excitatory type of reaction having a phasic chamber. Primary and secondary inhibitory reactions were noted among the spontaneously active neurons. The latent period of the excitatory reactions of the neurons of the centromedian nucleus varied from 5 to 33.6 msec (14.83 +/- 1.77 msec) and of the mediodorsal nucleus from 3.5 to 44.8 msec (18.03 +/- 2.5 msec). A high degree of convergence of reticular and somatovisceral signals on neurons of the centromedian nucleus (52.83%) and mediodorsal nucleus (53.5%) was found. An inhibitory type of interaction of central and peripheral influences was established.

Action Potentials↗
PubMed1990

Acute effects of vitamin B6 and fixed combinations of vitamin B1, B6 and B12 on nociceptive activity evoked in the rat thalamus: dose-response relationship and combinations with morphine and paracetamol.

Nociceptive activity was elicited in neurones of the thalamus by supramaximal electrical stimulation of afferent C fibres in the sural nerve of rats under urethane anesthesia. The fixed combination of vitamin B1, B6, and B12 (Neurobion) as well as of vitamin B6 administered by i.p. injection dose-dependently reduced the evoked nociceptive activity. The ED50 of Neurobion is 4.6 ml/kg (at 100 min after injection) and that of vitamin B6 is 189 mg/kg (at 90 min after injection). The minimum effective doses of Neurobion and vitamin B6 are 0.5 ml/kg and 40 mg/kg, respectively. When Neurobion or vitamin B6 were given at their minimum effective doses, and the minimum effective doses of morphine (0.025 mg/kg) or paracetamol (5 mg/kg) were injected i.v. 80 min later, i.e., when the maximum effect of higher doses of Neurobion or vitamin B6 was about to develop, no supraadditive effect developed. It is concluded that the antinociceptive effect caused by a single injection of Neurobion is largely due to vitamin B6. Vitamin B12 may contribute to this effect, whereas vitamin B1 alone exhibited only a slight effect on nociception. Moreover, it appears that Neurobion produces its antinociceptive effect after a single injection and after repeated administration during several days by different mechanisms so that the effect of analgesic agents is not enhanced following a single injection of Neurobion but may be enhanced after repeated administration of the compound.

Acetaminophen↗