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At least 973 records · Page 54Linked to original sources
PubMed1985

[Postnatal development of barreloid neuropils in the ventrobasal complex of mouse thalamus: a histochemical study for cytochrome oxidase].

Postnatal development of barreloid neuropils was studied in the ventrobasal complex of mouse thalamus. A single barreloid neuropil which topographically represented a corresponding facial vibrissa on the contralateral side was demonstrated as a solid reaction mass with the method for cytochrome oxidase. This architectural unit was called a vibrissa compartment. On postnatal Day 0, the nuclear area of the ventrobasal complex showed higher activity for the enzyme than in regions around, but no barreloids were seen. Barreloid neuropils became detectable on postnatal Day 3 in the dorsomedial subnucleus of the ventrobasal complex and the septal delimitation of barreloids was established on postnatal Day 6. The arrangement of barreloids showed a distinct orderlines similar to that of facial vibrissae on a horizontal section. Barreloid neuropils contained synaptic glomeruli ensheathed with glial processes, in which dendritic processes and their excrescences of nerve cells received large terminal knobs in well-organized manner. On postnatal Day 10, immature glomerular forms were found in barreloid neuropils. The synaptic glomerulus of mature type, however, was not formed till postnatal Day 13. The number of synaptic junctions was examined in barreloid neuropils from postnatal Day 3 to 21. The result that the growth rate of synaptic junctions was the highest in a short period from postnatal Day 10 to 13 suggested rapid maturation of barreloid neuropils in this period. On postnatal Day 21, several types of synaptic contacts became remarkable in matured glomeruli. One of them, a filamentous type with association of clear synaptic vesicles at presynaptic sites was indicated. And non-synaptic junctional complex accompaning tubular structures beneath dense materials at dendritic sites was remarked between terminal knobs and dendritic processes. From results the following conclusions are remarked that at the level of mouse thalamus, septal delimitation of vibrissa compartments appeared on postnatal Day 3 and was established until postnatal Day 6. On the other hand, barreloid neuropils containing glomerular synaptic complexes became a maturing state on postnatal Day 13, that is, about one week later after architectural compartmentalization.

Animals↗
PubMed1986

[The thalamus: motor functions].

Thalamic nuclei constitute the diencephalic relay system between different afferent systems and the telencephalon. The "motor" thalamus links cerebellar and pallidal afferents with the motor and pre-motor cortical regions. Separation of pallido-thalamo-cortical and cerebello-thalamo-cortical pathways is relatively complete: afferents of pallidal origin are relayed by thalamic nuclei VA, VLo and VLm and are projected onto prefrontal and supplementary motor areas whereas afferents of cerebellar origin are relayed in the VL and VPLo and then projected onto motor areas 4.6 and parietal areas 5 and 7. This report is concerned mainly with the analysis of the motor thalamus as a relay system for afferents of cerebellar origin. The anatomofunctional organization of the cerebello-thalamo-cortical tract possesses a topographic arrangement and also wide convergences and appears able to participate in the realization, through the motor cortex, of motor synergies and of co-ordinating postures and movements. The cerebello-cortical tract apparently plays a different role during learning of a movement and executing an automatized movement. For the latter, it is involved in their onset and in their completion. Its contribution to fine control of temporal parameters of motor commands or control of peripheral afferent messages is not decisive. During learning of a movement the cerebello-cortical tract plays a predominant role. According to Ito, the cerebellum is involved in the process of automatization of a movement, organized initially entirely by the cortex and then becoming progressively subcortical. Plasticity of cerebellar microcircuits could be the basis for these automatization processes expressed through the cerebello-thalamo-cortical tract.

Animals↗
PubMed1986

[Effect of stimulation of the sensory nucleus of the thalamus on dyskinesia and spasticity].

Intermittent electrical stimulation of thalamus sensory nucleus effectively controlled dyskinesiae in 4 patients with Dejerine-Roussy's painful thalamic syndrome, and clonus of legs in 2 patients with post-traumatic medullary paraplegia. Results of long-term follow-up of these 6 cases, with movements controlled by implantation of a system of electrical stimulation of the thalamus sensory nucleus, are reviewed.

Afferent Pathways↗
PubMed1986

[Relations between the basal ganglia and the thalamus of the primate. New morphologic data. New physiopathologic interpretations].

Considerable progress has been made over the last few years in our knowledge of the thalamus and basal ganglia and their relationships to the cerebral cortex. More detailed topographic studies in the macaque have demonstrated the separation, in the lateral region of the thalamus, between afferent cerebellar and basal ganglia territories. These territories fail to correlate with the subdivision between ventral and dorsal elements or the limits of a single cytoarchitectonic nucleus. The cerebellar territory corresponds to VIL (or VPLo) which projects towards the primary cortex, and to VIM (or area X) and DI (or VLc) which project towards premotor cortex. The nigral (and tectal) territory corresponds to VOM (or VAmc) and to some parts of the medial nucleus and projects mainly towards the oculomotor area, supplementary motor area and prefrontal cortex. In return, the oculomotor area and substantia nigra project towards the colliculus superior. Several thalamic nuclei constitute the pallidal territory: VOL (or VLo) projects mainly towards supplementary motor area, LPo (or VApc) and Do towards the prefrontal cortex. The median center, which receives afferents from pallidum and motor cortex, projects towards the striatum but also the motor cortex. The parafascicular nucleus projects towards the striatum and premotor cortex. It is still not possible to transpose data acquired in the macaque to man, but functional reinterpretations are possible. A system which involves the median pallidum, VOL and supplementary motor area could control motor initiative and flow of movement. A second system, involving the substantia nigra, colliculus superior, thalamic relay and oculomotor area could control posture. The pallidum and substantia nigra, anterior part of lateral mass, medial nucleus and prefrontal cortex could elaborate motor programmes.

Animals↗
PubMed1986

[Organization of the median and intralaminar nuclei of the thalamus: hypotheses on their role in the onset of certain central pain].

Afferent neurons from thalamic median and intralaminar (IL) nuclei arise in the spinal cord, brain stem synapses, substantia nigra, internal pallidum and cerebral cortex, directly and through the intermediary of the reticular nucleus of the thalamus (RT). Efferent neurons terminate in the anterior thalamic nuclei, RT, striatum and cerebral cortex. Tracking methods in the rat have demonstrated that some RT neurons which project towards the IL are surrounded by endings from the posterior ventral nucleus (VP). Electrical stimulation of multiple prosencephalic structures (mainly VP) and of sensory pathways induce responses in IL of brief latency followed by inhibition. Whereas the responses appear to be related to activation of excitatory projections (under the tonic facilitating control of cerebral cortex) the inhibition phases could be related to activation of RT, since they disappear after lesion of the RT. This nucleus could act as a common final pathway of inhibitions exerted on IL in the rat. Studies in this species have demonstrated that a lateral lesion of the thalamus that includes the RT provokes the appearance in IL of abnormal neuronal hyperactivity of a tonic nature and yet still exaggerated by stimuli normally capable of inducing responses of brief duration followed by inhibition. Human studies using a tomoscintigraphic method to determine regional blood flow have shown "hyperactivity" of the thalamic region in patients with pain of central origin during a natural stimulus provoking hyperpathia. This was not observed during painful states without hyperpathia. The working hypothesis proposed is that of a central lesion inducing a hyperpathia provoking pathologic hyperactivity in certain thalamic nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

[Motor symptomatology of the thalamus].

Muscular deficit, voluntary movement disorders, abnormal movements, and global disturbance of movements are considered. A muscular deficit is part of the Dejerine-Roussy syndrome. It appears as hemiparesis, regressive within days or weeks. A juxta-thalamic capsular involvement can be considered as the origin of this deficit in most cases, especially in hemorrhagic processes even if these are located within the thalamus, on account of mass effect. The occurrence of paresis or paralysis in ischemic processes strictly situated in the thalamus, however, is discussed: the deficit may be limited to parts of limbs; most often, it is not associated with pyramidal symptomatology; recovery is observed in the hand before the inferior limb. To these anatomoclinical facts some data from animal experiments or thalamic stereotaxic surgical procedures in humans must be added. A deafferentiation from the cortex seems to be the main cause of these motor disturbances. Three types of voluntary movement disorders may be encountered: contralateral cerebellar incoordination due to the involvement of the nucleus ventrooralis posterior where the superior cerebellar peduncle ends; homolateral imitative syncinesias, not confined to thalamic lesions, but frequently observed in this location with a particular aspect; contracture. Abnormal movements include choreoathetosic movements, and exceptionally intention and action tremor, and asterixis. They primarily involve the superior limb, but reported cases are not associated with thalamic limited lesions. Global disturbance of movements is observed in the hand or gait. "Thalamic hand" consists of incessant finger movements in the vertical and horizontal planes. They are associated with thalamic dystonia and deep sensibility disorder.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1985

[Visual-form thinking of patients before and after stereotaxic surgery on the ventrolateral nucleus of the thalamus].

An examination of patients with deformed muscular dystonia before and after stereotaxic surgery on the ventrolateral nucleus of the thalamus showed that prior to the surgery they had a certain difficulty in solving tasks involving mental manipulation with three-dimensional objects and constructive activity. It took them more time to accomplish these tasks and they made different mistakes as compared to normal. Changes in the object and image thinking differed, depending on the side of the destruction of the ventrolateral nucleus of the thalamus. Patients with right-side lesion were prone to overturn both a three-dimensional figure and a two-dimensional image, they showed greater changes in conducting tests on mental manipulation and constructive activity as against the patients who had left-side cryodestruction. It may be assumed that impairment of the complex forms of spatial functions manifested in mental manipulation with objects and in constructive activities is related to the work of the subcortical formations of the right hemisphere.

Adolescent↗
PubMed1985

A description of the GABAergic neurons and axon terminals in the motor nuclei of the cat thalamus.

The GABA neurons and their processes in the cat motor thalamic nuclei were identified and studied with glutamic acid decarboxylase (GAD) immunocytochemistry at both the light and electron microscopic levels. The three nuclei that comprise the motor thalamus, ventral anterior (VA), ventral medial (VM), and ventral lateral (VL), each displayed a characteristic distribution pattern of GAD-positive structures that was consistent with their afferent and intrinsic neuronal organization. All three thalamic nuclei displayed a population of small, GAD-positive cells the dendrites of which contained synaptic vesicles and participated in complex synaptic arrays such as serial synapses, triads, and glomeruli. Based on their ultrastructural features, these GAD-containing cells were identified as local circuit neurons. In contrast, the larger, GAD-negative cells were presumed to be the thalamocortical projection neurons. The axons of GAD-positive local circuit neurons could not be identified in these preparations. The number of GAD-positive dendrites in the neuropil was different for the three thalamic nuclei. In the VA and VM, the GAD-positive dendrites were numerous and formed symmetric synapses with dendrites of GAD-negative cells, mainly in association with corticothalamic boutons. Within VL, the GAD-containing dendrites were more numerous than in VA and VM and formed synapses at influential locations on presumed thalamocortical projection neurons, such as bases of primary dendrites, and bifurcation sites of primary and secondary dendrites. The VA and anterolateral VM nuclei that receive inhibitory GABAergic afferents from the entopeduncular nucleus and substantia nigra contained the highest concentration of large GAD-positive axon terminals. These boutons contained pleomorphic vesicles and numerous mitochondria and formed symmetric synapses and multiple puncta adherentes with dendrites and somata of presumed thalamocortical projection neurons. The size, ultrastructural features, and distribution of these GAD-positive boutons were similar to those features described for basal ganglia terminals in the motor thalamus of the cat. In addition, similar large-size GAD-positive boutons were observed in the medial VM, which receives basal ganglia afferents exclusively from the substantia nigra. The concentration of these terminals in medial VM along the dendrites of thalamocortical projection neurons was much less than that in VA and anterolateral VM. The VL nucleus which lacks basal ganglia input did not contain any large GAD-positive boutons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

[Functional significance of the spatial organization of efferent projections of the striopallidum to the cortex and thalamus].

A correlation has been found between spatial organization of efferent projections of the striopallidum to the cortex and the thalamus and the nature of behavioural reactions. A relative homogeneity of cellular structure of the striopallidal nuclei and a wide overlap of their efferent connections in the cortex and the thalamus are one of the causes of the common character of striate influences on behaviour. Differences of spatial organization of striate projections may be connected with functional heterogeneity of striate structures.

Animals↗
PubMed1995

Role of the dorsomedial nucleus of the thalamus in Alzheimer's disease.

It is not known whether changes in the thalamus play a role in the memory loss or dementia of Alzheimer's disease (AD), although trauma, infarction, and hemorrhage to the thalamus, particularly the dorsomedial nucleus (DMN), can cause these cognitive changes. To determine the pathologic changes in the DMN in AD, we examined the DMN in 16 cases of AD and 7 age-matched controls, with quantitative assessments of the total neuronal population and synaptic density, Alz-50-positive neurons, neurofibrillary tangles (NFT), and senile plaques (SP). We examined sections after staining with cresyl violet, a silver stain, and immunocytochemical staining for Alz-50 and synapsin I. Stereologic analysis demonstrated a mean loss of 29% of DMN neurons in AD and a synaptic density decrease of 21%. Alz-50 staining and NFT were present in all AD cases but in none of the controls. Senile plaques were 52 times more frequent in the DMN in AD than in the age-matched controls. The large variation in pathologic changes among our AD cases suggests that neuronal losses and other pathology in the DMN in AD may contribute to the total brain burden of pathology resulting in dementia in some AD patients, but not in others.

Aged↗
PubMed1994

Germinoma originating in the basal ganglia and thalamus: MR and CT evaluation.

PURPOSE: To describe MR and CT features of germinoma originating in the basal ganglia and thalamus and to discuss the roles of each modality for its diagnosis. METHODS: MR and CT studies of six cases of germinomas, five of which were histologically proved, were retrospectively reviewed. T1-weighted, T2-weighted, and contrast-enhanced T1-weighted conventional spin-echo images, and unenhanced and contrast-enhanced CT images were evaluated. RESULTS: Typically, the tumor consisted of an irregular solid area with contrast enhancement and various-size cysts. Cystic components were found in five cases and calcification in four. Intratumoral hemorrhage was noted in one. Ipsilateral cerebral hemiatrophy and brain stem hemiatrophy were noted in three cases each. MR was superior to CT in evaluating precise tumor extension, cystic components, and intratumoral hemorrhage, although in one case, extension of the tumor was better defined on CT in its early stage. Calcification was difficult to identify by MR alone. The solid components of the tumors generally showed slightly high density on CT, which seemed to be characteristic compared with nonspecific intensity pattern on MR. CONCLUSION: The combination of CT and MR findings allows early detection and appropriate diagnosis of the mass in the basal ganglia and/or thalamus.

Adolescent↗
PubMed1996

[A case of amnesic syndrome caused by hematoma in the left anterior medial thalamus].

We reported a case of amnestic syndrome caused by a hematoma in the left thalamus. The case was that of a 68-year-old, right-handed man who suddenly showed amnestic syndrome. He had neither motor paresis nor sensory disturbance. Clinical examination showed he had disorientation, anterograde amnesia and mild retrograde amnesia. Immediate recall and remote memory were intact, but recent memory was severely impaired. CT scan revealed a high density area in the anterior medial part of the left thalamus. We concluded that amnesia in this patient was caused by fasciculus mamillothalamicus damage because of a hematoma during thalamic hemorrhage.

Aged↗
PubMed1997

Role of Ca2+ ions in nicotinic facilitation of GABA release in mouse thalamus.

Presynaptic nicotinic acetylcholine receptors (nAChRs) are present in many regions of the brain and potentially serve as targets for the pharmacological action of nicotine in vivo. To investigate their mechanism of action, we performed patch-clamp recordings in relay neurons from slices of thalamus sensory nuclei. In these nuclei, nAChR activation facilitated the release of the inhibitory neurotransmitter GABA. Micromolar concentrations of nicotinic agonists increased the frequency of miniature GABAergic synaptic currents and decreased the failure rate of evoked synaptic currents. These actions of nicotinic agonists were not observed in knock-out mice lacking the beta 2 nAChR subunit gene. Nicotinic effects were dependent on extracellular calcium ions, and they persisted when calcium was replaced by strontium or barium but not by magnesium. Furthermore, in high extracellular calcium concentrations, nicotinic agonists evoked an increase in spontaneous release lasting for minutes after removal of the agonist. This supports the view that presynaptic nAChRs facilitate the release of neurotransmitter by increasing the calcium concentrations in presynaptic nerve endings. With use of cadmium and nickel ions as selective blockers, it was found that in different sensory nuclei the presynaptic influx of calcium could result either from the activation of voltage-dependent calcium channels or from a direct influx through nAChR channels. Finally, we propose that the nicotinic facilitation of GABAergic transmission may contribute to the increase of signal-to-noise ratio observed in the thalamus in vivo during arousal.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1976

[Influence of the somatic region of the cortex on trace inhibitory processes in the posterior lateral nucleus of the thalamus].

Acute experiments were conducted on cats under nembutal anesthesia. A study was made of the dynamics of the changes occurring in the curve of restoration of the test response amplitude in the thalamo-cortical fibers to the pared stimulation of the medial lemniscus with various actions on the somatosensory ared. The curve under study served as an indicator of the corticofugal influences on the inhibitory after process in the transmission nucleus of the thalamus. The influences on one somatosensory area of the cortex blocked the transmission of the afferent signals in 70% of the neurons of the transmission nucleus of the thalamus. A correlation between the number of the neurons participating in the reaction and the character of the initial phase of the inhibitory afterprocess was noted.

Animals↗
PubMed1964

ATTACK ELICITED BY STIMULATION OF THE THALAMUS OF CATS.

Electrical stimulation of sites in the medial thalamus leads to attack upon rats. This attack summates with attack elicited by hypothalamic stimulation. Stimulation of other thalamic sites suppresses hypothalamic attack, while excitation of still others facilitates it.

Aggression↗
PubMed1982

Symmetry and asymmetry in the human posterior thalamus. I. Cytoarchitectonic analysis in normal persons.

We parceled the posterior thalami of nine normal human brains according to cytoarchitectonic criteria, measured relevant nuclear volumes, and sought left-right asymmetries. We found that thalamic zones with multiple projections to the cerebral cortex, using the centromedian-parafascicular nucleus as a prototype, were mostly symmetric. This group includes the medial, lateral, and inferior pulvinar nuclei. Thalamic zones that project discretely to a few, clearly defined cortical receptor fields (using the medial geniculate nucleus [MG] as a prototype) closely reflected the asymmetry of the cortical fields to which they project. Hence, the MG showed a slight right-sided bias, and the lateralis posterior nucleus (related to the grossly asymmetric inferior parietal lobule) showed a significant leftsided bias in eight of the nine brains measured. This asymmetry may partially explain the apparent language specialization of the dominant thalamus.

Adolescent↗
PubMed1982

Symmetry and asymmetry in the human posterior thalamus. II. Thalamic lesions in a case of developmental dyslexia.

The cytoarchitecture of the brain of a patient with developmental dyslexia was analyzed. The cortical abnormalities, consisting of micropolygyria encompassing most of posterior temporoparietal area and ectopic cell collections elsewhere have been described previously. In this study, the posterior thalamus was likewise analyzed, and a bilateral disruption of cytoarchitecture was noted in the medial geniculate nucleus and the lateralis posterior nucleus, a nuclear group of probable relevance to language found to be asymmetric.

Cerebral Cortex↗
PubMed1996

Timecourse of development of the wallaby trigeminal pathway. II. Brainstem to thalamus and the emergence of cellular aggregations.

This paper is the second in a series which makes use of the protracted postnatal maturation of the wallaby to study the development of the trigeminal sensory system. Previous work has established similarities in the organisation of the trigeminal sensory system in the wallaby and in rodents. This study describes the structure and development of the ventroposteromedial nucleus in the wallaby in relationship to the arrival of afferents from the trigeminal nuclei, the formation of neuronal aggregations and naturally occurring cell death. Enzyme histochemistry, Nissl and myelin stains were used. Pathway development was followed using carbocyanine dyes. In the adult wallaby the nucleus demonstrates evidence of a parcellated organisation. Cells are arranged in dorsoventrally aligned bands resembling fingers. In the horizontal plane, these appear as circular clusters which are encircled by fine myelinated bundles. The clusters of cells are believed to correspond to the mystacial vibrissae. The first afferents from the principal trigeminal nucleus arrive between 10 and 15 days postnatal. This is more than two weeks prior to the time at which the borders of the nucleus can be discerned cytoarchitecturally. The first hints of segmentation are visible around day 50, and discrete aggregations form over the ensuing 3-4 weeks. Coincident with the aggregation of the neurons is an increase in their level of reactivity for acetylcholinesterase. A high level of acetylcholinesterase reactivity is maintained for at least 4 months, but has disappeared in adult animals. The peak of cell death occurs subsequent to the appearance of aggregations in the thalamus, but coincident with the appearance of vibrissae related patches in the cortex at day 85 (Waite et al. [1991] Dev. Brain Res. 58:35-41). The timing of the appearance of the neuronal aggregations supports the hypothesis that pattern formation occurs sequentially at successive levels of the pathway, and suggests the importance of target maturation in pattern formation.

Afferent Pathways↗