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PubMed1985

Vascular malformations of the thalamus with normal angiograms.

We describe two patients with fatal vascular malformations of the thalamus whom we thought had gliomas. They had progressive neurological impairment with subacute onset as adults. Computed tomography showed lesions of increased density with slight post-contrast enhancement; cerebral angiography was normal. Without biopsy, they received radiation therapy without benefit. Two other patients with similar radiological studies have done well with conservative treatment. We believe that these lesions have a distinctive appearance on CT, that vascular malformations can be diagnosed, even with normal cerebral angiograms, and distinguished with reasonable certainty from gliomas.

Adult↗
PubMed1990

Propriospinal neurons with ascending collaterals to the dorsal medulla, the thalamus and the tectum: a retrograde fluorescent double-labeling study of the cervical cord of the rat.

Branching neurons with descending propriospinal collaterals and ascending collaterals to the dorsal medulla, the thalamus and the tectum were studied in the rat's cervical spinal cord (C1-C8), using the retrograde fluorescent double-labeling technique: Diamidino Yellow Dihydrochloride (DY) was injected in the cord at T2, True Blue (TB) was injected in the brain stem. DY-labeled descending propriospinal neurons were present in all laminae, except lamina IX. They were concentrated in lamina I, laminae IV to VIII, and in the lateral spinal nucleus, LSN. TB-labeled neurons projecting to the dorsal medulla were concentrated in lamina IV and the medial parts of laminae V and VI (probably representing postsynaptic dorsal column--PSDC--neurons), but were also present in lamina I, the LSN, the lateral dorsal horn, and in laminae VII and VIII. DY-TB double-labeled neurons giving rise to both a descending propriospinal collateral and an ascending collateral to the dorsal medulla were intermingled with the TB single-labeled neurons. About 4% of the descending propriospinal neurons gave rise to an ascending collateral to the dorsal column nuclei; these double-labeled cells constitute a sizable fraction (10%) of the PSDC neurons. TB-labeled spinothalamic and spinotectal neurons were located in lamina I, the lateral cervical nucleus (LCN), and LSN, the lateral lamina V, lamina VII and VIII, lamina X and in the spinal extensions of the dorsal column nuclei, predominantly contralateral to the TB injections. DY-TB double-labeled neurons were present throughout C1-C8 in the LSN, lateral lamina V, lamina VIII, ventromedial lamina VII, and lamina X. Only very few were observed in lamina I and the LCN, and none in the spinal extensions of the dorsal column nuclei. The double-labeled neurons constituted only a minor fraction of all labeled neurons; 3-5% of the spinothalamic neurons and about 1-7% of the spinotectal neurons were double-labeled. Conversely, only about 1% of the labeled descending propriospinal neurons gave rise to an ascending spinothalamic collateral, and even fewer (0.1 to 0.6%) to a collateral to the dorsal midbrain. The LSN displayed the highest relative content of branching neurons. Up to 20% of its ascending spinothalamic and spinotectal neurons and up to 8% of its descending propriospinal neurons were found to be branching neurons, indicating that the LSN constitutes an unique cell-group in the rat spinal cord.

Animals↗
PubMed1991

Functional organization of the auditory thalamus in the guinea pig.

The auditory thalamus of the guinea pig was investigated with microelectrode mapping techniques. Pure tones of varying frequencies and amplitudes were used as acoustic stimuli, and frequency tuning curves were recorded from 840 multi-units or single cells. The neurons in ventral nucleus of the medial geniculate body (MGv) respond vigorously to pure tones; they have mostly narrow frequency tuning curves and short response latencies (8-12 ms). The MGv is tonotopically organized: High frequencies (16-21 kHz) are located rostrally; the intermediate frequencies (2.8-11 kHz) lie caudomedial of the high frequencies, while the low frequencies (0.5-2.8 kHz) run as a continuous band from rostrolateral to caudomedial. These data confirm a model of tonotopy of the guinea pig MGv which was based on anatomical data from previous tract-tracing experiments. In these experiments, thalamocortical connections were investigated with retrogradely transported tracers (horseradish peroxidase, fluorescent dyes, Redies et al. 1989b). Dorsal, lateral and in part also ventral to MGv, the neuronal responses to pure tones were often less vigorous than in MGv. Many neurons had broad frequency tuning curves, and in nearly all recordings from this region, the response latencies were longer than 12 ms. A tonotopic organization was not apparent here. From the response properties and the location relative to MGv, we concluded that this area corresponds to the shell nucleus of the MG.

Acoustic Stimulation↗
PubMed1996

Electrophysiological investigations of the somatosensory thalamus of the pigeon.

Somatosensory areas in the thalamus of the pigeon were studied electrophysiologically at the single-unit level. Of 459 units, 429 responded to somatosensory stimuli. Of these, 394 units responded specifically to somatosensory stimuli, whereas 8 responded in addition to visual stimuli and 27 to auditory stimuli also (bimodal neurons). Seven units were exclusively driven by visual stimuli and 23 units by auditory stimuli. Recording sites included nucleus dorsalis intermedius ventralis anterior (DIVA) and nucleus dorsolateralis posterior (DLP). The number of bimodal or visual and auditory neurons was much larger in DLP (40%) than in DIVA (7%). This points to a specific somatosensory function of DIVA. There was only a poor somatotopic organization in both nuclei. However, in vertical penetrations, wing representation was usually dorsal to leg representation. Distal parts of the limbs had smaller receptive fields (RFs) than proximal parts, and the smallest RFs were found on the toes, which seem to be represented in most detail.

Animals↗
PubMed1985

Role of intralaminar thalamus in gaze mechanisms: evidence from electrical stimulation and fiber-sparing lesions in cat.

Information on eye movement related activity in the internal medullary lamina (IML) of the thalamus is consistent with an IML role in the control of eye movements, or with its serving to convey information to the forebrain on impending events in the oculomotor system. Interpretation is impeded by the fact that eye movements evoked by electrical stimulation of the IML might be triggered by antidromic activation of projections to the IML from brainstem preoculomotor centers. In order to address this issue, thresholds for the elicitation of eye movements and cortical recruiting responses (as a marker for IML integrity) were studied before and after destruction of IML neuronal populations by the fiber-sparing neurotoxin ibotenic acid. Experiments were performed in alert cats chronically implanted with a scleral search coil for the monitoring of eye movements and an electrode-cannula assembly that permitted threshold determinations and drug injections at the stimulating site without any movement of probes in the tissue. Drastic elevation of the threshold for cortical recruiting responses, but not for eye movements following ibotenic acid destruction of IML neurons uncomplicated by myelin damage at the site of stimulation suggests an antidromic route for eye movements elicited by IML stimulation.

Animals↗
PubMed1996

Reevaluation of synaptic relationships of cerebellar terminals in the ventral lateral nucleus of the rhesus monkey thalamus based on serial section analysis and three-dimensional reconstruction.

Terminals of cerebellar afferents (CB) to different regions of the ventral lateral nucleus (VL) of the rhesus monkey thalamus were labeled with wheat germ agglutinin-horseradish peroxidase following injections into the dentate nucleus. Synaptic relationships of 17 CB with projection neuron dendrites (PNd) and local circuit neuron dendrites (LCNd) were analyzed in serial ultrathin sections from dorsal and ventral VL regions, which are known to differ cytoarchitecturally and functionally. Three terminals were reconstructed using three-dimensional (3D) computer image analysis techniques to obtain volumetric and planar measurements. CB in the ventral VL were often flat and elongated with synaptic vesicles arranged in clusters. Each CB was engaged with one PNd and one to four LCNd. A single bouton formed 8-50 synaptic contacts, with those on PNd outnumbering the ones on LCNd 4.1:1. Only some CB in the ventral VL were engaged in complex synaptic arrangements such as triads and serial synapses. Most CB in the dorsal VL displayed a roundish shape and numerous uniformly distributed synaptic vesicles. They formed 5-25 synaptic contacts with a 3:1 ratio of contacts on PNd compared with those on LCNd. CB in the dorsal VL participated in a variety of complex synaptic arrangements. Two types of triads were found: classic with CB, PNd and LCNd, and unconventional with CB and two LCNd. CB were also involved in serial synapses with two LCNd or LCNd and another PNd, and serial sequential synapses with two LCNd and a PNd. Three glomerulus-like structures were encountered in the dorsal VL. 3D reconstruction and volumetric measurements revealed that synaptic contacts formed by CB on PNd had varying shapes and sizes (0.022-0.274 microns2). Synapses formed on LCNd were larger (0.09-0.407 microns2). The total area of all active zones of a single CB on LCNd was either equal to or about 40% smaller than that of synapses on PNd. The entire active zone area comprised 1-1.6% of the total CB surface area and did not seem to correlate with the volume. Synaptic contacts formed by associated LCNd on PNd in complex arrangements were usually small (0.021-0.044 micron2). The results suggest that: synapses formed by CB on PNd and LCNd, and synapses formed by LCNd on PNd may differ in strength; a variety of different circuits participate in the processing of cerebellar afferent information in the primate VL; and these circuits differ in functionally different VL subdivisions.

Animals↗
PubMed1979

A combined horseradish peroxidase and Golgi study on the afferent connections of the ventrobasal complex of the thalamus in the cat.

Afferent connections to the ventrobasal complex (VB) of the thalamus were studied by means of retrograde transport of horseradish peroxidase (HRP) and by the Golgi-method. After HRP-injection into the VB, peroxidase-positive cells were observed contralaterally in the dorsal column nuclei (DCN), in the trigeminal nuclei and in the lateral cervical nucleus (LCN), and ipsilaterally in the somatosensoty I (SI) and II (SII) cortical areas. Labeled cells of different shape and size were compared with neurons impregnated by the Golgi-technique. On tn size and shape even within one region and that they correspond to the relay or efferent neurons observed in the Golgi-material.

Animals↗
PubMed1986

Pattern of pyramidal tract collateralization to medial thalamus, lateral hypothalamus and red nucleus in the cat.

Stimulating electrodes were placed in the red nucleus, lateral hypothalamus and medial thalamus in order to determine whether pyramidal tract (PT) neurons send collaterals to those sites. The red nucleus projections are well-known, but it was discovered that PT neurons also project into the other two sites. All of the fibers that sent collaterals to all three sites originated from fast PT neurons. Those that responded to stimulation of the skin and that sent collaterals to two or three sites were predominantly fast PT neurons. Those neurons that responded only to cerebral peduncle stimulation were predominantly slowly-conducting, when compared with the set of PT neurons in response to cerebral peduncle stimulation. The patterns of collateral branching to red nucleus and to lateral hypothalamus were similar, suggesting a similar synaptic effect of the pyramidal system in the two sites. Measurement of the speed of conduction from three sites along the length of corticospinal fibers revealed large changes on some, but not all, fibers; there was no evident pattern to these changes that might be associated with collateral branching. A new hypothesis concerning the functional role of fast PT neurons in regulating movement is presented.

Anesthesia↗
PubMed1986

Direct retinal pathways to the limbic thalamus of the monkey.

Tritiated proline, horseradish peroxidase (HRP), and wheat germ agglutinin conjugated to HRP (WGA-HRP) were used as anterograde tracers in the monkey to reveal visual pathways. After intravitreal injections, three separate, direct routes of labeled retinal axons were followed to the thalamus. These routes eventually converged to innervate the lateral dorsal and anterodorsal thalamic nuclei. Thus, retinal input may reach the posterior cingulate cortex after a single synapse in lateral and anterior thalamic nuclei.

Animals↗
PubMed1981

Neuronal responses in the rat's thalamus to scrotal heating.

Twenty-one single neurons from the rat's thalamus were recorded as they responded to scrotal skin thermal stimulation. Eighteen of them were warm and three inverse-warm cells. After the injection of Lidocain (Xylocain) into the scrotal skin, the response of each neuron was abolished. Eight neurons could be followed until the drug effect had disappeared; their responsiveness was fully restored. External application of Xylocain had the same effect as intracutaneous injection, apart from longer time intervals before the effect became apparent. From this, conclusions are drawn on the origin of the thalamic responses, and speculations are made on the functional role of warm and inverse-warm cells.

Animals↗
PubMed1986

Cytochrome oxidase staining reveals functional organization of monkey somatosensory thalamus.

Histochemical staining for a mitochondrial enzyme, cytochrome oxidase demonstrates elongated, rod-like configurations of probable axon terminals in the trigeminal representation of the monkey somatic sensory thalamus. The stained rods are colocalized with similar aggregations of immunocytochemically stained GABAergic thalamic interneurons. Other data suggest the rods also contain clusters of relay neurons projecting to cortical columns, and they are here demonstrated as somatotopic units by micro-electrode mapping and the distribution of afferent fibers. Similar somatotopic rods can be revealed in the rest of the thalamic body representation by the reduction in cytochrome oxidase staining ensuing from the cutting of selected peripheral nerves.

Afferent Pathways↗
PubMed1987

Thresholds and encoding of neuronal responses to mechanical stimuli in the ventro-basal thalamus during carrageenin-induced hyperalgesic inflammation in the rat.

Neuronal response thresholds and the encoding of mechanical stimulus intensity in the ventro-basal (VB) thalamus was analyzed in anaesthetized rats before and during the first two hours following induction of hyperalgesic inflammation. This inflammation was induced by the intra-plantar injection of carrageenin in the hindpaw contralateral to the recorded neurones. Only neurones exclusively driven by noxious stimuli and with a receptive field on or including the injected paw were considered. In this early phase of the inflammatory process, there was no significant modification of the response threshold to the mechanical stimulus (indentation of about 300 micron). This suggests the involvement of additional neuronal population(s) to account for the decrease in the vocalisation threshold to pressure observed in the freely moving animal at this time of the inflammation. A liner encoding of the indentation depth was observed before and after the carrageenin injection although the slope of the stimulus response-curve was steeper after the injection. The data emphasize that the carrageenin-sensitization acts differentially on the liminal and supra-liminal responses of the same neurone to a skin indentation, since in the first hour following the initiation of the inflammation the sensitization is essentially observed for responses obtained with stimulus intensity largely above the threshold value. With regard to previous observations using thermal stimulation, the results also illustrate that the carrageenin induced sensitization of responses differs depending on the stimulus intensity and modality used.

Animals↗
PubMed1987

Organization of the projections from barrel cortex to thalamus in mice studied with Phaseolus vulgaris-leucoagglutinin and HRP.

In order to elucidate the geometric organization of projections from the barrel cortex to the thalamus, iontophoretic injections of the anterograde tracer Phaseolus vulgaris-leucoagglutinin were made. The injections were confined to one barrel column (i.e. barrel in layer IV + cortical tissue above and below it). Axonal terminations could be demonstrated in three thalamic nuclei: reticularis (RT), ventrobasalis (VB) and posterior (PO). Anterograde terminal labelling was obtained in RT + VB; in PO only; or in RT + VB + PO. The terminals labelled in PO were much larger than those in RT and VB. The termination areas in RT, VB and PO were shaped like rods which have a rostro-caudal orientation. These cortico-thalamic projections are discretely and topographically organized. The clearest such arrangement was found in VB. Here, projections from the A row of barrels in BF terminate dorsally, whereas those from the C row end ventrally. Barrel A1 projects to the lateral part of VB, whereas A4, to more medial parts; other rows are arranged similarly. These results were compared with the distribution of thalamo-cortical projection neurons that were labelled after iontophoretic HRP injections in individual barrels. We concluded that the corticothalamic projections originating from one barrel column contact an are of barreloids in VB.

Animals↗
PubMed1990

Germ cell tumors of the thalamus and the basal ganglia.

Two cases of germ cell tumors (GCTs) of the basal ganglia are presented and 40 previously reported cases are reviewed. The incidence of GCTs of the basal ganglia and thalamus was estimated as less than 14% of all intracranial GCTs. All patients except for two (95%) were male, aged 7-19 years. The clinical course was usually slow. The major symptoms were hemiparesis, mental deterioration such as dementia or character change, precocious puberty, diabetes insipidus, oculomotor palsy, speech disturbance, and hemianopsia. Signs of intracranial hypertension did not occur until the late stages of the disease. The plain CT finding was characterized by an irregularly defined, slightly high-density area frequently accompanied by central low-density areas without significant mass effect. The tumors showed mild to moderate and nonhomogeneous contrast enhancement. An ipsilateral cerebral hemiatrophy was often found. MR images demonstrated the corresponding findings. GCTs of the basal ganglia had a high possibility of containing components other than germinoma such as choriocarcinoma, endodermal sinus tumor, and embryonal carcinoma. Thus, tumor markers in the serum, CSF, or cyst fluid were frequently positive. With recent refinement of microsurgical techniques as well as immunohistochemical study and measurements of tumor markers of serum, CSF, and cyst fluid, major resections of tumor, accurate pretreatment histologic diagnosis, and early determination of the specific types of this tumor appear to be readily possible. This is essential for effective treatment of patients not only with radiosensitive germinoma, but also those with radioinsensitive nongerminoma variants and a combination of them located in this region.

Adolescent↗
PubMed1984

Neuronal types in the neocortex-dependent lateral territory of the human thalamus. A Golgi-pigment study.

Nerve cell types of the neocortex-dependent nuclei of the human thalamus were investigated with the use of a transparent Golgi technique, that allows one to study not only the peculiarities of the cell processes, but also the marking characteristics of the intraneuronal lipofuscin pigment deposits. Three principal types of neurons have been distinguished: Type I is a medium-sized to large neuron with a profusely radiating dendrite system. Numerous large vacuolated lipofuscin granules are contained in one pole of the cell body. Type II is a small to medium-sized neuron with a few sparsely branching dendrites. Small and intensely stained pigment granules are dispersed within the cell body. Type III is a medium-sized to large neuron with only a few thick and almost unbranched dendrites devoid of spiny appendages. The dendrites extend over long distances. The cell body is devoid of lipofuscin granules.

Aged↗
PubMed1995

Familial neurofibromatosis 1 with germinoma involving the basal ganglion and thalamus.

Intracranial germinoma associated with neurofibromatosis 1 (NF-1) has never been documented previously. We report a case of familial NF-1 with a germinoma involving the right basal ganglion and thalamus. A 12-year-old boy presented with multiple café-au-lait spots and a family history of neurofibromatosis in his mother, one of two siblings, and his maternal grandfather. His intracranial lesion was subtotally resected. Histologically, it was a pure germinoma. Serum alpha-feto protein and beta-human chorionic gonadotropin levels were within the normal range. Postoperative myelographic examination and cerebrospinal fluid cytology study showed no evidence of subarachnoid seeding. The patient received postoperative combination chemotherapy resulting in complete response and clearance of the residual tumor. Although this finding of an intracranial germinoma in a patient with familial NF-1 may be coincident, it is suggestive of a potential genetic predisposition. Longitudinal evaluation for the possibility of neoplasm, especially germ cell tumor, in basal ganglion lesions in NF-1 patients is necessary.

Basal Ganglia↗
PubMed1977

Adrenergic modulation of a cholinergic emotional reaction in the cat's thalamus.

Direct carbachol stimulation of the intralaminar nuclei of the thalamus evokes an affective defense reaction in the cat. Pretreatment of the region with noradrenaline inhibited the reaction in a dose-related manner. Phenylephrine was ineffective in this respect while isoprenaline exhibited roughly the same inhibitory action as noradrenaline. The alpha-receptor blocking dihydroergotamine left the inhibitory effect of noradrenaline unaffected while the beta-receptor blocking propranolol abolished it. These findings suggest that the inhibitory effect of noradrenaline on the carbachol-induced thalamic emotional reaction is caused by its influence on beta-type adrenergic receptors. Since a similar adrenergic-cholinergic interaction was previously demonstrated also for the hypothalamus and red nucleus, it can be concluded that adrenergic modulation of cholinergic reactions in the central nervous sytem seems to be a principle of more general validity than has been assumed thus far.

Animals↗