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PubMed2005

[The peculiarities of speech disturbance in patients with arteriovenous malformations of the caudate nucleus and the thalamus].

Clinical and neuropsychological study of 28 patients with arteriovenous malformations (AVM) of the caudate nucleus and 36 patients with AVM of the thalamus has been conducted. After surgical removal of the caudate nucleus, speech disturbances developed in 4 out of 8 patients with left-side AVM and in 1 patient, a converted left-hander, with right-side AVM. All 5 patients had mild speech disturbances, which differed by character in dependence of the AVM location. In case of AVM location in the head of the caudate nucleus, the speech disturbances were represented by perseverations and were similar to those caused by the lesion in the Broca area. In case of the caudate nucleus lesion, naming was mildly affected that resembled temporal aphasia. After surgical removal of AVM in the left thalamus in 9 patients, complex and rather stable speech disturbances developed in 7 cases. They were featured by the signs of frontal and temporal aphasias, i.e. there were perseverations and disturbances of naming, auditory and speech memory. The peculiarities of speech disturbances in lesions of the caudate nucleus and the thalamus were well explained by their anatomic and functional correlations with different regions of brain speech cortex. Speech disturbances in various subcortical lesions are reviewed. In the authors' opinion, subcortical aphasias do not have any particular character but include the same factors in different combinations as cortical ones that is determined by the presence of common functional systems for speech support which comprise cortical and subcortical patterns.

Adolescent↗
PubMed1991

[Anatomic connections between homotopic transplant of fetal cortical tissue and optic thalamus in adult rats].

The present research was planned to study the possibility to reconstruct a damaged neural circuitry by replacing the injured neurons with homotopic fetal cells. In adult rats the motor cortex was injured with intracortical injection of kainic acid solution. After a delay of 10-14 days, a block of cerebral cortex of fetal rats (E17) was transplanted in the cavity produced by the kainic acid in the motor cortex. After 2-3 months, WGA-HRP solution was injected in the thalamus of the host and both anterogradely labeled fiber terminals and retrogradely labeled somata cells were researched in the transplanted cortex. The results showed that: 1) the host thalamus projects to the transplanted cortex with less density compared to the host cortex surrounding the transplant; 2) the thalamic projection to the transplant is not topographically organized whereas the projection to the host cortex is; 3) the transplant was virtually void of a significant projection to the thalamus of the host. In conclusion, the results offer direct evidence that the reconstruction of an injured thalamocortical circuitry of adult rat is not possible by transplanting homotopic fetal neurons.

Animals↗
PubMed1990

Alterations on the distribution of methionine-enkephalin-like in the cat thalamus after electroacupuncture: an immunocytochemical study.

The distribution of methionine-enkephalin-like structures in the cat thalamus after electroacupuncture was studied using an indirect immunoperoxidase technique. We have observed some alterations on the distribution of methionine-enkephalin-like fibres in the thalamus of the cat after electroacupuncture. Thus, in the nuclei habenularis lateralis and lateralis dorsalis, in the tractus mamillo-thalamicus and in the tractus habenulopeduncularis, we have found methionine-enkephalin-like fibres in the animals treated with electroacupuncture, however in such nuclei and tractus no immunoreactivity was observed in the control animals. On the contrary, after electroacupuncture we have not found methionine-enkephalin-like fibres in the thalamic nuclei centrum medianum, parascicularis and subparafascicularis, in which in the animals no pretreated with electroacupuncture, immunoreactive fibres were observed. In other thalamic nuclei such as habenularis medialis, paraventricularis anterior, centralis medialis, medialis dorsalis and in the stria medullaris no alteration on the distribution of immunoreactive fibres was observed in the animals treated with electroacupuncture in comparison with the distribution of such fibres found in the control animals. These observations suggest that the electroacupuncture might induce alterations on the distribution of methionine-enkephalin-like in certain nuclei of the thalamus of the cat.

Animals↗
PubMed1990

[Generalized nocifensor reflexes--II. A modified reflex pattern caused by functional disorders of the thalamus].

In the past, clinically relevant diagnostic procedures using nocifensive reflexes have been restricted mainly to ascertaining the functional status of the efferent or afferent portion of the reflex arc. The method described here, which evoked global nocifensive reflexes, permits differentiated conclusions to be drawn regarding possible supraspinal influences on nocifension. The reflex patterns yielded by the procedure can provide information regarding the functional status of the formatio reticularis, which is subject to modulatory influences of the pallidostriatum and thalamus. The results show that specific, pathohistologically confirmed lesions of the thalamus de-inhibit the formatio reticularis for motor reticulospinal activity and that this is reflected in the nocifensive pattern. Thus, the nocifensive reflex on the contralateral side to the thalamic process is stronger and has a shorter latent time than that on the clinically healthy side. This phenomenon has so far been confirmed on all patients with an impaired thalamus function.

Humans↗
PubMed1990

Topographic organization of neurons in the acoustic thalamus that project to the amygdala.

Projections from the posterior thalamus to the amygdala have been implicated in the processing of the emotional significance of acoustic stimuli. The aim of the present studies was to determine which areas of the amygdala receive afferents from posterior thalamic structures that, in turn, receive afferents (presumably acoustic afferents) from the inferior colliculus. Projections from the posterior thalamus to the amygdala and striatum were examined in rats using anterograde and retrograde axonal transport techniques. Following injections of WGA-HRP into the posterior thalamic areas [including the medial division of the medial geniculate body, the posterior intralaminar nucleus (PIN) and the medial posterior complex (POM)], anterograde transport was seen in the lateral (AL), central (ACE), medial (AM), and basomedial (ABM) nuclei of the amygdala and in the amygdalostriatal transition area (AST) and posterior caudate putamen (CPU). Injection of WGA-HRP into each anterogradely labeled area produced retrograde transport to the posterior thalamus, but the pattern of transport varied with the site of the injection. Injections in AL and AST produced retrograde transport to neurons in the medial division of the medial geniculate body (MGM), PIN, suprageniculate nucleus (SG) and, to a lesser extent, the lateral posterior nucleus (LP). Injections of the ACE, AM, and ABM, in contrast, only labeled cells in POM. While the MGM, PIN, and SG each receive afferents from the inferior colliculus, POM does not. AL and AST, therefore, receive inputs from thalamic areas that, in turn, receive inputs from the inferior colliculus.

Amygdala↗
PubMed1990

[Reading and writing deficit in cases of localized infarction of the left anterior thalamus].

We have observed two cases with marked reading and writing deficits, in which speech and oral comprehension were generally intact. Detailed symptomatological study was performed on these cases, and the lesions were examined organically (X-ray computed tomography [X-ray CT], magnetic resonance imaging [MRI] and functionally (positron emission tomography [PET]. In addition to the marked reading and writing deficits, mild naming and memory disorders were found. X-ray CT and MRI revealed that the lesions were limited to the regions fed by the polar and paramedian arteries in the left thalamus. In one case, PET demonstrated a functional disturbance of the left parietal and temporal lobes in addition to the left thalamus. Most previous cases have shown lesions in the anterior portion of the thalamus. It is possible that the reading and writing deficits in these cases may be due to the thalamic lesion itself, but the PET findings strongly suggest that a secondary cortical lesion may be involved in producing the higher cognitive disorders.

Aged↗
PubMed1989

The thalamus of the dog: a tridimensional and cytoarchitectonic study.

The organization of the thalamus varies considerably from species to species. This article reports a tridimensional study of the canine thalamus in which 18 nuclei were distinguished on the basis of their delimitation in sections and their differing cytoarchitectonic characteristics, the latter having been objectively quantified by means of an image analyser. On the basis of their location and/or mutual similarities, these 18 nuclei are classified in 5 groups. The thalamus of the dog is similar to that the cat, but differs considerably from those of other well-studied species.

Animals↗
PubMed1989

[The effect of the calcium antagonists nimodipin, verapamil and diltiazem on local cerebral blood flow of the cortex and thalamus in cats].

Experiments were carried out on 54 cats, anesthesized by ether and alpha chloralose (0, 1 g/kg of b. m.) and the influence of calcium antagonists nimodipin (0.01 and 0.03 mg/kg), verapamil (0.1 and 0.3 mg/kg) and diltiazem (0.1 and 0.3 mg/kg), administered intravenously by a femoral venous catheter, was investigated on th local cerebral blood flow in the cortex and thalamus by means of a thermistor thermoclearance technique. The cerebral blood flow was recorded in the sensomotor area of the cortex-and pulvinar thalami. The effect of these drugs was examined on arterial blood pressure in dynamics synchronously. Calcium antagonist nimodipin, verapamil and diltiazem increased cerebral blood flow and this effect was more manifested in the cortex than in the thalamus. The effect of nimodipin was considerably stronger on the cerebral blood flow in the cortex in comparison with verapamil and diltiazem. Verapamil and diltiazem showed approximately equal effect on cerebral blood flow in the cortex. Diltiazem increased cerebral local blood flow, but not-that of the thalamus.

Animals↗
PubMed1978

[Experimental cerebral infarction. Part 2: EEG change in experimental thalamus infarction in the dog--it's value and application (author's transl)].

Athough it has been generally believed that it is extremely difficult to prepare an experimental model of cerebral infarction in the dog with the use of temporary vascular occlusion, the procedure recently developed by one of the authors fascilitates the production of a localized infarction in the thalamus with a noticeably high rate of success. To obtain more reliability of this method, techniques of electroencephalography induced from depth electrode to the thalamus were applied in this experiment. Following a temporary vascular occlusion, a significant diminution of fast wave component of about 10 Hz occurred with attenuation of voltage in the ipsilateral thalamic depth electrode. In cases of 2 hour vascular occlusion done by this method, an obvious infarction in the thalamus was confirmed histologically 7 days later. The authors emphasised that when the experimental model of thalamic infarction in the dog are combined with EEG, not only can cerebral infarction be producted with more certainly but also the EEG changes can be followed. This analysis is important since it provides information on the chronological changes in the ischemic region or infarction lesion.

Animals↗
PubMed1984

[Sensitivity of neurons in the rabbit thalamus parafascicular complex to angiotensin II during stimulation of the ventromedial hypothalamus].

A study was made of the sensitivity of parafascicular neurons of the thalamus to angiotensin II (A-II) applied microiontophoretically. Almost half of the neurons investigated (48,5%) were discovered to be sensitive to the peptide. Stimulation of the ventromedial hypothalamus provoked marked changes in the pattern of the responses of parafascicular neurons of the thalamus to A-II. The data obtained suggest that the sensitivity of parafascicular neurons of the thalamus, the pattern of responses to biologically active substances may be altered dynamically under the influence of excitations evoked by stimulation of the hypothalamus.

Angiotensin II↗
PubMed1995

The role of the thalamus in functional neurosurgery.

The human thalamus has been the focus of much interest as a target organ for the stereotactic surgical modification of particularly pain and movement disorders. The sites receiving the greatest attention are portions of Vc, Vim, Vop, and the medial thalamus. As such procedures require physiologic corroboration of target site, a considerable literature has arisen concerned with electrical stimulation and microelectrode recordings within them. Not only do the physiologic observations accomplish the desired localization, but they also allow an insight into normal and pathologic thalamic physiology. Yet vast areas of the thalamus remain unstudied enigmas.

Brain Mapping↗
PubMed1976

The diencephalon of the vervet monkey (Cercopithecus aethiops). Part I: thalamus and metathalamus.

The diencephalon of the vervet monkey (Cercopithecus aethiops) is described and compared with that of other primates, particularly the macaque monkey (Macaca mulatta). In the vervet monkey, the thalamus is divided into six nuclear groups: anterior, midline, medial, dorsolateral, ventrolateral and posterior. The anterior nuclear group shows a regressive nucleus anterodorsalis and a poorly defined demarcation between the nuclei anteromedialis and anteroventralis. There is a large interthalamic adhesion in which the ventral region containing nuclei centralis medialis, interventralis and reuniens, shows more regression than the dorsal region consisting of nuclei parataenialis and paraventralis. As the nucleus medialis ventralis is not present, the nucleus medialis dorsalis is described as the nucleus medialis; this is clearly differentiated into three parts, each part showing different cytological and architectonic features. The nucleus centrum medianum is larger and better developed than that of lower primates but is not entirely demarcated from the nucleus parafascicularis. The pulvinar is an enormous outgrowth from the dorsolateral thalamic nuclei. The ventrolateral thalamic nuclei are well differentiated from one another: a distinct nucleus ventralis dorsomedialis is present and appears to possess definite topographical and cytological differences from those of the other ventrolateral nuclei. The nucleus ventralis posteromedialis is further differentiated into a magno- and a parvocellular part. The nucleus ventralis posteroinferioris is a distinct entity. The lateral geniculate body shows a definite differentiation into two nuclei: pregeniculate and lateral geniculate nuclei. The lateral geniculate nucleus is a six-layered structure which is of the inverted type; it has undergone a lateral rotation through an anteroposterior axis from a dorsal position in the prosimian thalamus to its present ventral position in the higher primate thalamus. The medial geniculate body is not laminated as is the lateral geniculate nucleus; it consists of a small dorsomedial magnocellular and a large ventrolateral parvocellular part.

Animals↗
PubMed1997

Nitric oxide production in rat thalamus changes with behavioral state, local depolarization, and brainstem stimulation.

Since its discovery as a putative neurotransmitter in the CNS, several functional roles have been suggested for nitric oxide (NO). However, few studies have investigated the role of NO in natural physiology. Because NO synthase (NOS) has been localized in regions believed to be important for attention and arousal, we hypothesized that NO production would be state-dependent. To test this hypothesis, we used in vivo microdialysis, coupled with the hemoglobin-trapping technique, to monitor extracellular NO concentrations in rat thalamus during wake, slow-wave sleep (SWS), and rapid eye movement (REM) sleep. The thalamus is known to receive a massive innervation from the NOS/cholinergic neurons in the mesopontine brainstem, which have been suggested to play a key role in EEG desynchronized states. To test whether thalamic NO output was sensitive to neuronal-dependent changes in the mesopontine brainstem, we measured thalamic NO concentration in response to electrical stimulation in the laterodorsal tegmentum (LDT) of anesthetized rats. Finally, the calcium dependence of NO release was tested by local depolarization with a high potassium dialysate or by addition of a calcium chelator. The results showed that (1) extracellular NO concentrations in the thalamus were high during wake and REM sleep and significantly lower during SWS, (2) thalamic NO release increased in response to LDT stimulation in both a site-specific and tetrodotoxin (TTX)-dependent manner, and (3) NO production was calcium-dependent. These data suggest that thalamic NO production may play a role in arousal.

Animals↗
PubMed1997

Spatiotemporal patterns of spindle oscillations in cortex and thalamus.

Spindle oscillations (7-14 Hz) appear in the thalamus and cortex during early stages of sleep. They are generated by the combination of intrinsic properties and connectivity patterns of thalamic neurons and distributed to cortical territories by thalamocortical axons. The corticothalamic feedback is a major factor in producing coherent spatiotemporal maps of spindle oscillations in widespread thalamic territories. Here we have investigated the spatiotemporal patterns of spontaneously occurring and evoked spindles by means of multisite field potential and unit recordings in intact cortex and decorticated animals. We show that (1) spontaneous spindle oscillations are synchronized over large cortical areas during natural sleep and barbiturate anesthesia; (2) under barbiturate anesthesia, the cortical coherence is not disrupted by transection of intracortical synaptic linkages; (3) in intact cortex animals, spontaneously occurring barbiturate spindle sequences occur nearly simultaneously over widespread thalamic territories; (4) in the absence of cortex, the spontaneous spindle oscillations throughout the thalamus are less organized, but the local coherence (within 2-4 mm) is still maintained; and (5) spindling propagation is observed in intact cortex animals only when elicited by low intensity cortical stimulation, applied shortly before the initiation of a spontaneous spindle sequence; propagation velocities are between 1 and 3 mm/sec, measured in the anteroposterior axis of the thalamus; increasing the intensity of cortical stimulation triggers spindle oscillations, which start simultaneously in all leads. We propose that, in vivo, the coherence of spontaneous spindle oscillations in corticothalamic networks is attributable to the combined action of continuous background corticothalamic input initiating spindle sequences in several thalamic sites at the same time and divergent corticothalamic and intrathalamic connectivity.

Anesthesia↗
PubMed1997

Apoptosis is restricted to the thalamus in thiamine-deficient rats.

Thiamine deficiency (TD) produces lesions in the thalamus, mamillary and medial geniculate nuclei, and inferior colliculus. To clarify the pathogenesis of these lesions, we examined the occurrence of hallmarks of apoptosis following TD in rat brain. Histological assessment showed apoptotic cells in the thalamus and medial geniculate nucleus but not in the inferior colliculus. We used terminal deoxynucleotidyl transferase-mediated deoxyuridine (dUPT)-biotin nick-end labelling (TUNEL) and gel electrophoresis to demonstrate that TD is associated with apoptotic cell death. In the thalamus, DNA fragmentation appeared from day 14 of deficiency and preceded the appearance of ataxia. The inferior colliculus and mamillary nucleus were without electrophoretic DNA fragments, and only rare TUNEL-positive labelling was observed. This model shows a rare combination of both apoptosis and necrosis in the same lesioned brain.

Animals↗
PubMed1998

A specific role for the thalamus in mediating the interaction of attention and arousal in humans.

The physiological basis for the interaction of selective attention and arousal is not clearly understood. Here we present evidence in humans that specifically implicates the thalamus in this interaction. We used functional magnetic resonance imaging to measure brain activity during the performance of an attentional task under different levels of arousal. Activity evoked in the ventrolateral thalamus by the attentional task changed as a function of arousal. The highest level of attention-related thalamic activity is seen under conditions of low arousal (secondary to sleep deprivation) compared with high arousal (secondary to caffeine administration). Other brain regions were also active during the attentional task, but these areas did not change their activity as a function of arousal. Control experiments establish that this pattern of changes in thalamic activity cannot be accounted for by nonspecific effects of arousal on cerebral hemodynamics. We conclude that the thalamus is involved in mediating the interaction of attention and arousal in humans.

Adult↗
PubMed1997

Subcellular distribution of AMPA and NMDA receptor subunit immunoreactivity in ventral posterior and reticular nuclei of rat and cat thalamus.

Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) selective glutamate receptors mediate excitatory neurotransmission in the somatosensory thalamus, but morphological localization of the receptors at identified thalamic synapses has been lacking. The authors used electron microscopic immunocytochemistry to localize AMPA selective GluR 2/3 subunits (GluR2/3) and NMDA receptor subunit 1 (NMDAR1) in rat and cat ventral posterior lateral nucleus (VPL) and in the associated sector of the reticular nucleus (RTN). Light microscopy showed that GluR2/3 and NMDAR1 immunolabeled neurons are homogeneously distributed in both nuclei. The relationship between glutamate receptor labeled profiles and glutamate or gamma-aminobutyric acid (GABA) labeled synapses was revealed by combining preembedding and postembedding immunostaining at the electron microscopic level. GluR2/3 and NMDAR1 immunoreactivity was located in somata and in proximal and distal dendrites of VPL relay cells and of RTN cells. Immunoreactivity was concentrated in postsynaptic densities of glutamatergic synapses and absent from postsynaptic densities of GABAergic synapses. In the cat, GluR2/3 and NMDAR1 immunoreactivity was also localized in GABAergic interneurons, including their presynaptic dendrites (PSD). Of the GluR2/3 and NMDAR1 labeled thalamic synapses observed, 10-29% were lemniscal (RL) type synapses in VPL; 60-70% were corticothalamic (RS) type synapses in the VPL and RTN. In the cat, 7-19% were identified as PSD profiles, and more NMDAR1 labeled PSD were found in the VPL than in the RTN. The main findings were as follows: 1) AMPA selective GluR2/3 and NMDAR1 share similar distribution patterns in the rat and cat somatosensory thalamus, 2) both glutamate receptors are likely to be colocalized at postsynaptic densities of both RL and RS synapses, and 3) localization of the glutamate receptor proteins in GABAergic dendrites in the cat thalamus indicates that glutamatergic transmission to GABAergic neurons is also mediated by both NMDA and non-NMDA receptors.

Animals↗
PubMed1998

Projection and innervation patterns of individual thalamic reticular axons in the thalamus of the adult rat: a three-dimensional, graphic, and morphometric analysis.

The gamma-aminobutyric acid-ergic thalamic reticular nucleus (Rt), which carries matching topographical maps of both the thalamus and cortex and in which constituent cells can synaptically communicate between each other, is the major extrinsic source of thalamic inhibitions and disinhibitions. Whether all the Rt axonal projections into the thalamus are similarly organized and have common projection and innervation patterns are questions of great interest to further our knowledge of the functioning of the Rt. The present study provides architectural and morphometric data of individual, anterogradely labeled axonal arbors that arose from distinct parts of the Rt. One hundred twenty-seven Rt neurons from all regions of Rt were marked juxtacellularly with biocytin or Neurobiotin in urethane-anesthetized adult rats. Eighteen two-dimensional and 14 three-dimensional reconstructions of single tracer-filled Rt neurons were made from serial, frontal, horizontal, or sagittal sections. Both the somatodendritic and axonal fields of tracer-filled Rt cells were mapped in three dimensions and illustrated to provide a complementary stereotaxic reference for future studies. Most marked units projected to a single nucleus of the anterior, dorsal, intralaminar, posterior, or ventral thalamus. Axons emerging from cells in distinct sectors of the Rt projected to distinct nuclei. Within a sector, neurons with separate dendritic fields innervated separate regions either in a single nucleus or into different but functionally related thalamic nuclei. Neurons with an overlap of their dendritic fields gave rise either to overlapping axonal arborizations or, more rarely, to distinct axonal arbors within two different thalamic nuclei implicated in the same function. In rare instances, an Rt axon could project within these two nuclei. Thalamic reticular axons commonly displayed a single well-circumscribed arbor containing a total of about 4,000 +/- 1,000 boutons. Every arbor was composed of a dense central core, which encompassed a thalamic volume of 5-63 x 10(6) microm3 and was made up of patches of maximal innervation density (10 +/- 4 boutons/tissue cube of 25 microm each side), surrounded by a sparse component. The metric relationships between the Rt axonal arbors and the dendrites of their target thalamocortical neurons were determined. Both the size and maximal innervation density of the axonal patches were found to fit in with the somatodendritic architecture of the target cells. The Rt axonal projections of adult rats are thus characterized by their (1) well-focused terminal field with a patchy distribution of boutons and (2) parallel organization with a certain degree of divergence. The role of the Rt-mediated thalamic inhibition and disinhibition may be to contrast significant with nonrelevant ongoing thalamocortical information.

Animals↗