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At least 19 recordsLinked to original sources
PubMed2000

Coherence between cerebellar thalamus, cortex and muscle in man: cerebellar thalamus interactions.

Local field potentials (LFPs) were recorded in seven unanaesthetized patients between the four adjacent contacts of a macroelectrode stereotactically implanted for the treatment of tremor. The LFPs were presumed to arise predominantly from the nucleus ventralis intermedius (Vim) of the thalamus, the implantation target. They were recorded simultaneously with the ipsilateral EEG and contralateral EMG during an isometric contraction or at rest. The patients had a history of either isolated tremor (essential tremor, n = 2; benign tremulous Parkinson's disease, n = 1) or tremor with signs of a cerebellar syndrome (multiple sclerosis, n = 3; essential tremor and ataxia, n = 1), although clinical tremor was absent at the time of recording because of a temporary microthalamotomy effect in four patients. In patients with isolated tremor, oscillatory activity picked up by contacts in Vim (cerebellar thalamus) was invariably coherent with that in the sensorimotor cortex or contracting muscle in the 8-27 Hz range. Such coherence was absent in two of the four subjects with tremor associated with a cerebellar syndrome. Coherence between LFPs recorded from more caudally placed contacts and the sensorimotor cortex or contracting muscle was negligible in all patients. These caudally placed contacts demonstrated the highest sensory evoked potential in response to median nerve stimulation. Oscillatory activity in the cerebellar thalamus (Vim) lagged behind that in both cortex and muscle. Coherent activity between the cerebellar thalamus (Vim) and the cortex persisted at rest. It is suggested that rhythmicities in the 8-27 Hz range could provide the basis for a temporal framework that is widely distributed within the motor system.

Aged↗
PubMed1977

Neurogenesis in the epithalamus, dorsal thalamus and ventral thalamus of the rat: an autoradiographic and cytological study.

Times of final mitotic division for neurons of the epithalamic, dorsal thalamic and subthalamic nuclei of the rat were determined with the aid of thymidine-H3 autoradiography. Intensely labelled neurons were observed in the brains of animals injected with radiochemical from days 13 to 19 of gestation. The pattern of distribution of the labelled neurons indicated that neurogenesis in the regions followed caudorostral, lateromedial and ventrodorsal neurogenetic gradients, all of which were found to operate simultaneously. Since neurogenesis in the epithalamus, subthalamus and caudolateral thalamic regions began on days 13 and 14 of gestation, the ventrodorsal and lateromedial proliferative gradients were clearly discerned only within the ventral and dorsal thalamus exclusive of the epithalamus. These directional neurogenetic gradients were apparent throughout the entire thalamus and within individual thalamic nuclei. No neurogenetic pattern based upon neuronal size was observed, i.e., large neurons were not preferentially formed earlier than smaller ones. Detailed information has also been provided on the cytological character of each thalamic nucleus.

Animals↗
PubMed2000

Improved functional outcome in patients with hemorrhagic stroke in putamen and thalamus compared with those with stroke restricted to the putamen or thalamus.

BACKGROUND AND PURPOSE: We analyzed the effect of late intensive inpatient rehabilitation on the functional outcome of patients with subcortical hemorrhagic stroke. METHODS: Patients who were nonambulatory with hemorrhagic stroke in the internal capsule and putamen (n=55), the thalamus (n=24), or all 3 regions (n=15) underwent intensive inpatient rehabilitation. Patients with surgical intervention or an episode of ventricular hemorrhage were excluded. Lesion location was evaluated by MRI 4 months after the ictus. RESULTS: Demographic data, initial disability, and impairment measures were comparable in the 3 groups. Functional outcome demonstrated significant differences in mobility subscores (P<0.05) of the Functional Independence Measure such that patients with injury in the 3 regions were more likely to ambulate independently than were patients in the other groups. Lesion location data demonstrated that the ventral anterior nucleus of the thalamus was always spared; the ventral posterior (lateral and medial) nucleus was always damaged, and the ventral lateral nucleus was frequently damaged. Putaminal damage always included the postcommissural area. In addition, the entire posterior half limb of the internal capsule was always damaged. CONCLUSIONS: Subcortical lesions to multiple structures in the basal ganglia-thalamocortical motor circuits permitted enhanced motor recovery. Lesion location predicted the level of independent ambulation and the rate of recovery in patients with stroke who were nonambulatory before neurorehabilitation therapy.

Aged↗
PubMed1987

Converging cerebellofugal inputs to the thalamus. I. Mapping of monosynaptic field potentials in the ventrolateral nucleus of the thalamus.

The extent of thalamic projections from punctate sites in the cerebellar nuclei was examined in 22 acutely prepared cats by mapping monosynaptic field potentials evoked in the ventrolateral (VL) nucleus by stimulation of the interpositus and dentate nuclei (IN and DN). The monosynaptic field potentials were evoked in the VL by low current stimulating pulses applied at high frequency to these cerebellar nuclei. Quantification of the projections was possible since the conditions of stimulation and recording were strictly controlled. The incoming volley recorded in the brachium conjunctivum caudally to the VL was also analysed. It was composed of two amplitude peaks with different latencies, corresponding to two groups of fibres conducting at 60-90 m/s and 20-25 m/s respectively. The negative field potentials in VL also showed two amplitude peaks and different latencies. The differences in latency between the first and second peaks in the presynaptic and postsynaptic field potentials are compatible with the possibility that both groups of afferent fibres may be monosynaptically connected to VL relay cells. The cerebello-thalamic projections were mapped and their density gradient was established. Two or three small thalamic strips of dense projections surrounded by a large zone of weaker projections were observed to emerge from each punctate cerebellar site. In the discussion of the functional significance of these findings, it is suggested that this organization might constitute a modulatable morphological support for a mechanism focalizing the cerebello-cortical inputs.

Action Potentials↗
PubMed1980

[Correlation between the thalamus EEG and rCBF in the thalamus infarction in the dogs (author's transl)].

We have made an investigation of the correlation between the changes in thalamic EEG and rCBF immediately following occlusion 4 arteries at the base of the brain using thalamic infarction model with 38 dogs. Changes in EEG patterns due to vascular occlusion were divided into 4 grades. A tendency was found for decreases in rCBF to be greater the more marked were the EEG changes. Animals showing mild EEG changes in which there was only slight attenuation of voltage had rCBF values roughly 63% those prior to occlusion; animals with moderate EEG changes in which there was voltage attenuation and an increase in slow wave components had rCBF values of 34%; and animals with severe EEG changes in which there was voltage attenuation and complete disappearances of fast wave components showed rCBF values of roughly 29%.

Animals↗
PubMed1994

Whisker stimulation metabolically activates thalamus following cortical transplantation but not following cortical ablation.

Local cerebral glucose utilization was assessed during whisker stimulation by 2-deoxyglucose autoradiography. Whisker stimulation increased local cerebral glucose utilization in brainstem, thalamus and whisker sensory cortex in normal rats. Whereas whisker stimulation increased glucose metabolism in brainstem, whisker stimulation failed to increase glucose metabolism in thalamus of rats that had whisker sensory cortex ablated 5 h to five weeks previously. The failure of whisker stimulation to activate thalamus after cortical ablations was probably not due to decreased cortical input to thalamus because whisker stimulation activated thalamus after large cortical tetrodotoxin injections. Failure of whisker stimulation to activate thalamus at early times (5 h and one day) after cortical ablations was not due to thalamic neuronal death, since it takes days to weeks for axotomized thalamic neurons to die. The failure of whisker stimulation to activate thalamus at early times after cortical ablations was likely due to the failure of trigeminal brainstem neurons that project to thalamus to activate axotomized thalamic neurons. This might occur because of synaptic retraction, glial stripping or inhibition of trigeminal brainstem synapses onto thalamic neurons. The thalamic neuronal death that occurs over the days and weeks following cortical ablations was associated with thalamic hypometabolism. This is consistent with the idea that the thalamic neurons die because of the absence of a cortically derived trophic factor, since the excitotoxic thalamic cell death that occurs following cortical kainate injections is associated with thalamic hypermetabolism. The glucose metabolism of parts of the host thalamus was higher and the glucose metabolism in surrounding nuclei lower than the normal side of thalamus in rats that sat quietly and had fetal cortex transplants placed into cavities in whisker sensory cortex five to 16 weeks previously. Whisker stimulation in these subjects activated the contralateral host thalamus and fetal cortical transplants. This was accomplished using a double-label 2-deoxyglucose method to assess brain glucose metabolism in the same rat while it was resting and during whisker stimulation. The high glucose metabolism of parts of host thalamus ipsilateral to the fetal cortical transplants is consistent with prolonged survival of some axotomized thalamic neurons. The finding that whisker stimulation activates portions of host thalamus further suggests that the cortical transplants maintained survival of the host thalamic neurons and that synaptic connections between whisker brainstem and thalamic neurons were functional.

Animals↗
PubMed2003

Two epochs in the development of gamma-aminobutyric acidergic neurons in the ferret thalamus.

These studies chart the development of gamma-aminobutyric acid (GABA)-ergic neurons in the three divisions of the thalamus (ventral thalamus, dorsal thalamus, and epithalamus). GABAergic neurons were identified by in situ hybridization to localize mRNA for 67-kDa glutamic acid decarboxylase (GAD(67)) and related to the morphological maturation of the thalamus in fetal and postnatal brains and to expression of transcription factors Gbx-2 and Tbr-1. Origins of GABAergic neurons were sought in in vitro slice preparations incubated in bromodeoxyuridine or injected with a carbocyanine dye. GABA neurons of ventral thalamus (reticular nucleus, ventral lateral geniculate nucleus, zona incerta, and nucleus of the fields of Forel) and of epithalamus appear at least 14 days before those intrinsic to dorsal thalamus. Ventral thalamus GABA cells are derived from a region connecting the ventricular zone of the third ventricle to the caudal ganglionic eminence. This region is delimited ventrally by the Tbr-1-expressing prethalamic eminence and dorsally by the Gbx-2-expressing part of the dorsal thalamus. GABA neurons of epithalamus are derived from the embryonic pretectum. Neurons continue to be added to the ventral thalamus, perireticular nucleus, entopeduncular nucleus, and substantia nigra from the ganglionic eminence as development proceeds. GAD(67)-expressing cells of dorsal thalamus become detectable only at birth and populate the thalamus from posterior to anterior over the first week of life. Although a very small number reaches the dorsal lateral geniculate nucleus from the caudal ganglionic eminence, there is no obvious new source of proliferating neurons at this stage. Intrinsic GABA cells of dorsal thalamus may, therefore, derive from an early generated population of cells that turns on a GABAergic phenotype only late in development.

Animals↗
PubMed1979

Development of the diencephalon in the rat. V. Thymidine-radiographic observations on internuclear and intranuclear gradients in the thalamus.

Groups of pregnant rats were injected with two successive daily doses of 3H-thymidine from gestational days 13 and 14 (E13 + 14) until the day before birth (E21 + 22). Internuclear and intranuclear cytogenetic gradients were examined in radiograms of the thalamus sectioned in the coronal, sagittal and horizontal planes. There was a precise and segregated lateral-to-medial gradient between and within the habenular nuclei. In the ventral thalamus the reticular nucleus had a lateral-to-medial gradient, the subthalamic nucleus a laterodorsal-to-medioventral gradient. There was a caudal-to-rostral gradient between the medial geniculate and dorsal lateral geniculate nuclei, and between the pars posterior and pars anterior of the lateral nucleus. A clear intranuclear gradient could not be detected in the sensory relay nuclei with the exception of the medial geniculate nucleus. A lateral-to-medial internuclear gradient was seen between the relay nuclei and the intralaminar nuclei, and between the latter and some of the midline nuclei. On the basis of a consideration of the time of origin and time span of production of neurons of various thalamic nuclei, and taking into account some of the recognizable internuclear and intranuclear gradients, the thalamus was divided into five principal cytogenetic components; the epithelamus, the ventral thalamus, the dorsal thalamus, the medial thalamus, and the posterior thalamus. The epithalamic nuclei form over a protracted period resembling the nuclei of the hypothalamus. The nuclei of the ventral thalamus are generated early and over a relatively long period. The dorsal thalamus consists of the relay nuclei and the intralaminar nuclei; they form rapidly and ahead of the medial thalamus. The medial thalamus was subdivided into the earlier-forming anteromedial nuclei and the latest-forming midline nuclei. The posterior thalamus was not examined in detail.

Animals↗
PubMed1989

Cells of origin of spinothalamic tract projections to the medial and lateral thalamus in the cat.

The double fluorescent retrograde labeling method was used to examine the distribution of spinothalamic tract (STT) cells that project to the medial and lateral thalamus in the cat. Injections of one fluorescent tracer (Fast Blue or Diamidino Yellow) were made throughout the lateral thalamus and injections of the other tracer were made in the medial thalamus at sites extrapolated from recording track coordinates. Survival times were successively extended (up to 5 weeks) in order to maximize labeling in both the cervical and lumbosacral spinal cord. On average, over 2,000 labeled contralateral STT cells were counted in serial sections from segments C5-7 and L5-S2. Numerical variability of the order of a factor of two was attributable to inherent differences between individual animals. The total number of cells labeled with fluorescent tracers was comparable to the number labeled with horseradish peroxidase in control cases, although there were significant differences between the laminar distributions of labeling produced by the two methods. Injections made anterior to the thalamus to control for labeling due to leakage or passing fibers did not produce substantial spinal labeling. The laminar distribution of fluorescent dye-labeled STT cells was consistent; about half (47%) were located in lamina I, 8% were in lamina V, 5% in lamina VI, 20% in lamina VII, and 20% in lamina VIII. The proportions of STT cells in laminae I and V were higher in cervical segments (57% and 12%, respectively) than in lumbosacral segments (38% and 6%). The dominant contribution of lamina I cells to the STT thus revealed by the fluorescent tracers is striking. The proportions of STT cells labeled from the medial and the lateral thalamus varied with segmental and laminar location and with injection placement. The majority (62%) of STT cells in most cases projected only to the medial thalamus, 25% projected only to the lateral thalamus, and 13% projected to both. The STT cell populations in laminae I, VII, and VIII each displayed this common projection pattern. In contrast, cells in laminae V and VI projected predominantly to the lateral thalamus. Twice as many STT cells in lamina I (19%) projected to both the medial and the lateral thalamus as from other laminae. A greater proportion of laminae V-VIII STT cells in segments L5-6 projected to the lateral thalamus, and in S1-2, more projected to the medial thalamus.(ABSTRACT TRUNCATED AT 400 WORDS)

Amidines↗
PubMed1994

The evolution of the dorsal thalamus of jawed vertebrates, including mammals: cladistic analysis and a new hypothesis.

The evolution of the dorsal thalamus in various vertebrate lineages of jawed vertebrates has been an enigma, partly due to two prevalent misconceptions: the belief that the multitude of nuclei in the dorsal thalamus of mammals could be meaningfully compared neither with the relatively few nuclei in the dorsal thalamus of anamniotes nor with the intermediate number of dorsal thalamic nuclei of other amniotes and a definition of the dorsal thalamus that too narrowly focused on the features of the dorsal thalamus of mammals. The cladistic analysis carried out here allows us to recognize which features are plesiomorphic and which apomorphic for the dorsal thalamus of jawed vertebrates and to then reconstruct the major changes that have occurred in the dorsal thalamus over evolution. Embryological data examined in the context of Von Baerian theory (embryos of later-descendant species resemble the embryos of earlier-descendant species to the point of their divergence) supports a new 'Dual Elaboration Hypothesis' of dorsal thalamic evolution generated from this cladistic analysis. From the morphotype for an early stage in the embryological development of the dorsal thalamus of jawed vertebrates, the divergent, sequential stages of the development of the dorsal thalamus are derived for each major radiation and compared. The new hypothesis holds that the dorsal thalamus comprises two basic divisions--the collothalamus and the lemnothalamus--that receive their predominant input from the midbrain roof and (plesiomorphically) from lemniscal pathways, including the optic tract, respectively. Where present, the collothalamic, midbrain-sensory relay nuclei are homologous to each other in all vertebrate radiations as discrete nuclei. Within the lemnothalamus, the dorsal lateral geniculate nucleus of mammals and the dorsal lateral optic nucleus of non-synapsid amniotes (diapsid reptiles, birds and turtles) are homologous as discrete nuclei; most or all of the ventral nuclear group of mammals is homologous as a field to the lemniscal somatosensory relay and motor feedback nuclei of non-synapsid amniotes; the anterior, intralaminar and medial nuclear groups of mammals are collectively homologous as a field to both the dorsomedial and dorsolateral (including perirotundal) nuclei of non-synapsid amniotes; the anterior, intralaminar, medial and ventral nuclear groups and the dorsal lateral geniculate nucleus of mammals are collectively homologous as a field to the nucleus anterior of anamniotes, as are their homologues in non-synapsid amniotes. In the captorhinomorph ancestors of extant land vertebrates, both divisions of the dorsal thalamus were elaborated to some extent due to an increase in proliferation and lateral migration of neurons during development.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2003

Electrical properties affecting discharge of units of the mid and posterolateral thalamus of conscious cats.

Discharge properties in response to intracellularly applied, rectangular currents were measured in units of the mid (lateralis dorsalis and centrolateral nuclei) and posterolateral (lateralis posterior and pulvinar nuclei) thalamus of conscious cats. A separate aim was to determine if neuronal excitability changed in association with changes in stimulus-evoked activity after the animals were trained to discriminate between two acoustic stimuli when performing a conditioned motor response. Low threshold spike (l.t.s.) discharges were observed in three of 272 cells given 1 nA intracellular, hyperpolarizing current pulses of 40 ms duration. This finding supports the view that thalamic neurons of conscious animals operate mainly in the relay as opposed to the oscillatory mode. Application of larger and longer hyperpolarizing currents in the cells produced rebound l.t.s. discharges, supporting the expectation that most thalamic neurons are capable of producing this type of discharge. Decrements of spike afterhyperpolarizations (AHP) and broadening of spike bases upon repeated discharge also were observed in each area of the thalamus studied. After conditioning, changes were found in the posterolateral thalamus (but not in the mid-thalamus) in the proportions of cells with spontaneous, rapid (>/=50 Hz), repetitive, discharges (RRD) and rapid, sustained discharges at rates >/=100 Hz during application of depolarizing current (RSD). In the posterolateral thalamus the percentage of units responding to 1 nA depolarization with RSD fell from 71% before conditioning to 45% after conditioning. The percentage of cells with RRD decreased from 69% to 46%. The changes were accompanied by a 3 mV hyperpolarization of the membrane potentials of the cells and a decrease in baseline activity. After conditioning, increases in excitability were found in cells of the mid thalamus that responded selectively to the click conditioned stimulus (CS) that elicited the conditioned response, and decreases in excitability were found in cells of the posterolateral thalamus that responded to the discriminative acoustic stimulus (DS) to which the animals were trained not to respond. An earlier study showed a potentiation of discharge in response to the CS in units of the midthalamus after similar conditioning and a reduction of the proportion of DS responsive units and peak discharge to the DS in units of the posterolateral thalamus. We conclude that the discharge properties of units of the mid and posterolateral thalamus can change to support discrimination between acoustic stimuli of different functional significance after conditioning.

Acoustic Stimulation↗
PubMed1991

Serotoninergic innervation of the thalamus in the primate: an immunohistochemical study.

Little is known of the serotoninergic innervation of the thalamus in primates; therefore, we undertook a detailed study of the distribution of 5-hydroxytryptamine (5-HT)-immunoreactive neuronal profiles in the thalamus of the squirrel monkey (Saimiri sciureus) with a specific antibody directly raised against 5-HT. All thalamic nuclei in the squirrel monkey displayed 5-HT-immunoreactive fibers, but none contained immunopositive cell bodies. The 5-HT innervation of the thalamus derived from extrinsic fibers arising mostly from the midbrain raphe nuclei and forming the transtegmental system. Most of the fibers destined to the thalamus collected into a major bundle that swept dorsoventrally within the midbrain tegmentum and coursed beneath the thalamus along its entire caudorostral extent. Several fiber fascicles broke off from this main bundle at different levels and ascended dorsally to innervate the various thalamic nuclei. Overall, the 5-HT innervation of the thalamus in the squirrel monkey was more massive than would have been expected from earlier studies in nonprimate species. Marked differences in the regional density of innervation were noted both between the various nuclei and within single nuclei. The most densely innervated nuclei were those delineating the principal subdivisions of the thalamic mass, that is, the midline, rostral intralaminar, limitans, and reticular nuclei, where very dense fields of isolated axonal varicosities occurred. In contrast to the rostral intralaminar nuclei, which were rather uniformly innervated, the centre médian/parafascicular complex contained immunoreactive fibers and isolated varicosities distributed according to a mediolateral gradient. The habenula and the ventral anterior nucleus were among the most weakly innervated nuclei. In the latter nucleus, as well as in more densely innervated nuclei, thin varicose fibers formed numerous pericellular contacts on cell bodies and proximal dendrites of thalamic neurons. The 5-HT innervation of the lateral nuclear group as well as that of the medial and lateral geniculate nuclei ranged from very weak to dense. The mediodorsal nucleus displayed a highly heterogeneous 5-HT innervation that varied from weak in its central portion to moderate or dense in its medial and lateral borders. A moderate 5-HT innervation was observed in the anterior nuclear group. The surprisingly dense and heterogeneous 5-HT innervation of the thalamus noted in the present study suggests that serotonin may be involved in several specific functions of the thalamus in primates.

Animals↗