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PubMed1991

Corticofugal modulation of the information processing in the auditory thalamus of the cat.

Single unit activity of 355 cells was recorded in the auditory thalamus of anesthetized cats before, during, and after the inactivation by cooling of the ipsilateral primary auditory cortex (AI). Most of the units (n = 288) showed similar functional characteristics of firing before and after the cryogenic blockade of AI. The spontaneous firing rate remained unchanged by cooling in 20% of the units and decreased in the majority of them (60%). In some regions, i.e. dorsal division of the medial geniculate body (MGB), lateral part of the posterior group of the thalamus, and auditory sector of the reticular nucleus of the thalamus, the maximum firing rate evoked by white noise bursts was generally affected by cooling in the same direction and to the same extent as the spontaneous activity. Units in the ventral division of MGB showed a characteristic increase of signal-to-noise ratio during cortical cooling. The corticofugal modulation led to the appearance or disappearance of the best frequency of tuning in 51 units and changed it by more than 0.5 octave in 34 units. The bandwidths of different response patterns to pure tones stimulation were used to define a set of functional properties. During cryogenic blockade of AI, two cortically modulated sub-populations of units were usually distinguished that exhibited changes for a given functional property. The complexity and diversity of the effects of cortical inactivation suggest that the corticothalamic projection may be the support for selective operations such as an adaptive filtering of the incoming acoustic signal at the thalamic level adjusted as a function of cortical activity.

Acoustic Stimulation↗
PubMed1991

Neurons of the pretectal area convey spinal input to the motor thalamus of the cat.

The aim of this study was to corroborate lesioning work (Mackel and Noda 1989), suggesting the pretectal area of the rostral midbrain acts as a relay between the spinal cord and the ventrolateral (VL) nucleus of the thalamus. For this purpose, extracellular recordings were made from neurons in the pretectal area which were antidromically activated by stimulation in the rostral thalamus, particularly in VL. The neurons were tested for input from the dorsal columns of the spinal cord, the dorsal column nuclei, and the ventral quadrant of the spinal cord. Latencies of the antidromic responses ranged between 0.6 and 3.0 ms (median 1.0 ms): no differences in latencies were associated with either location of the neurons in the pretectal area or with the site of their thalamic projection. Orthodromic responses to stimulation of ascending pathways were seen in the majority of neurons throughout the pretectal area sampled. Latencies of orthodromic responses varied considerably, with ranges of 0.9-9 ms, 6-20 ms, and 2.5-20 ms upon stimulating the dorsal column nuclei, dorsal columns, and ventrolateral quadrant, respectively. The shortest-latency responses to stimulation of the dorsal column nuclei or of the ventral quadrant were likely to be monosynaptic. Temporal and spatial facilitation of the responses to ascending input were common. The data show that neurons of the pretectal area are capable of relaying somatosensory input ascending from the spinal cord to the rostral thalamus. It is suggested that the pretectofugal output to VL converges with cerebellar input in VL neurons and becomes incorporated in cerebello-cerebral interactions and, ultimately, the control of movement.

Animals↗
PubMed1975

Types of neuronal responses in the rat thalamus to peripheral temperature changes.

Recordings were made of spike-trains from 163 neurons of the rostral part of the ventrobasal thalamus complex of the rat while the temperature of the scrotal skin was altered. The following results were obtained: 55 neurons were non-thermosensitive, 7 neurons cold-sensitive and 101 neurons warm-sensitive. In the case of the warm-sensitive cells a definite discrimination was possible: 61.4% of the neurons altered their firing behavior during peripheral cooling, changing from relatively even spike frequency to burst firing. This change could be induced repeatedly by altering the temperature. 38.6% of the neurons, on the other hand, reacted to cooling by slowing down their frequency. By way of statistical methods the firing patterns of the two response-types were analyzed more precisely and the differences in response to temperature stimuli more exactly defined. Likewise, the spatial distribution of the two response-types of warm-sensitive cells exhibited differences; whereas the cells devoid of burst activity occured rather uniformly in the region of the thalamus studied, the cells with bursting activity were confined more to the mediocaudal region. These findings are discussed with regard to the phenomenon of peripheral bursts and to the projection of thermoafferent pathways onto the ventrobasal thalamus complex. The functional interpretation of the various cell reactions and their role in the central processing of thermoafferent signals still remains unexplained and requires comparative studies of peripheral and central parts of the thermoafferent system.

Animals↗
PubMed1982

Prelimbic cortex, mediodorsal thalamus, septum, and delayed alternation in rats.

Rats were trained preoperatively on contingently reinforced alternation in a T-maze. Then different matched groups of rats received lesions in the prelimbic cortex, mediodorsal thalamus, posterodorsal septum (aimed at transecting the precommissural fornix), and control operations (no brain lesions). Following a 2-week recovery period the rats were retested in the T-maze for retention of delayed alternation. Control rats were unaffected by the control operations and the testing hiatus of the recovery period. Rats with lesions in the prelimbic cortex performed at chance levels on the first postoperative session as did rats with posterodorsal septal lesions, but both groups recovered with continued experience, i.e., they could relearn the task. Rats with lesions in mediodorsal thalamus were only slightly affected by the lesions. The results suggest that a restricted field in the medial pregenual cortex, the prelimbic area, is critically involved in T-maze alternation. However, the data also suggest that a major subcortical source of afferents to prelimbic cortex, the mediodorsal nucleus of the thalamus, is not crucial for retention of contingently reinforced T-maze delayed alternation following interference with septo-hippocampal circuitry is consistent with data previously reported.

Animals↗
PubMed1988

Topography of basal glucose utilization in rat thalamus and hypothalamus determined with (1-14C)-glucose.

High resolution autoradiography was used to study the basal pattern of glucose-utilization in the rat thalamus and hypothalamus. Rats were injected via chronic jugular catheter with (1-14C)-glucose and sacrificed 30 min later. The high resolution thaw-mount autoradiographic procedure, using 4 micron frozen sections and nuclear emulsion, permitted discrimination of regional variations in glucose-utilization that have not yet been described. Quantitative data were obtained by means of digital image analysis and computerized densitometry. In the thalamus, high activity was present in the anterodorsal, anteroventral, laterodorsal and reticular nuclei, while low activity was found in the mediodorsal and paraventricular nuclei. The autoradiographic pattern of glucose utilization in the thalamus corresponds largely to classical cytoarchitectonic subdivisions. In the hypothalamus, the median eminence, arcuate nucleus, and periventricular nucleus showed the lowest activity, whereas certain parts of the lateral hypothalamus appeared high. Very high activity was present in mammillary nuclei. The described detailed anatomical data of glucose-utilization may provide insights into the functional circuitry of thalamic and hypothalamic systems and serve as a baseline from which experimental manipulations can be assessed.

Animals↗
PubMed1983

A neuropathologic study of Werdnig-Hoffmann disease with special reference to the thalamus and posterior roots.

The brains of five cases of severe infantile form of Werdnig-Hoffmann (W-H) disease were studied to observe the pathologic changes of sensory neurons and the thalamus. The present study disclosed severe cell loss, chromatolytic degeneration, and empty cell beds of the spinal anterior horn and cranial motoneurons (V, VII, X, XII). Glial bundles were also noted in the anterior roots. In the sensory systems, glial bundles in the posterior roots (2/5), ghost cells in Clarke's column (2/5), and degeneration of the thalamus, mainly in the lateral formation (4/4) were noted. It was demonstrated that not only degeneration of lower motor neurons and glial bundles in the anterior roots, but also degeneration of sensory neurons and thalamus were present in W-H disease. These findings suggested the possibility that W-H disease is a multisystemic disease involving both the anterior and posterior root systems. No sensory involvement was found clinically. Characteristic wrist drop was observed in four cases, two of which also having motor nerve conduction velocity (MCV) delay. On the other hand, MCV of another case without wrist drop was normal. The possibility that wrist drop might be one of the clinical features of peripheral nerve dysfunction was discussed, but further pathologic evaluation of peripheral nerves is needed.

Female↗
PubMed1989

Intracytoplasmic inclusion bodies of the thalamus and the substantia nigra, and Marinesco bodies in myotonic dystrophy: a quantitative morphological study.

Intracytoplasmic inclusion bodies of the thalamus and the substantia nigra, and Marinesco bodies have been studied in four patients with myotonic dystrophy (MyD), eight patients with other neurological diseases (control A), and eight patients without neurological diseases (control B). The percentages of the affected cells were calculated by dividing the number of neurons including intracytoplasmic inclusion bodies of the thalamus and the substantia nigra, and Marinesco bodies, by the total cell count in these respective regions. Statistical analyses were performed with regard to the frequency of these bodies by using Student's t test. There was a significantly higher incidence of intracytoplasmic inclusion bodies of the thalamus (13.2% versus 0.7%, P less than 0.001) and the substantia nigra (20.4% versus 2.7%, P less than 0.001), and Marinesco bodies (37.4% versus 4.1%, P less than 0.001) in patients with MyD than in controls A and B. From our observations, it is suggested that the presence with a high frequency, in combination, of these bodies is not an incidental finding but may have an intimate and important relationship with the pathogenesis of MyD, and may be a conspicuous and diagnostically important feature of MyD.

Adult↗
PubMed1996

Trends in the anatomical organization and functional significance of the mammalian thalamus.

The last decade has witnessed major changes in the experimental approach to the study of the thalamus and to the analysis of the anatomical and functional interrelations between thalamic nuclei and cortical areas. The present review focuses on the novel anatomical approaches to thalamo-cortical connections and thalamic functions in the historical framework of the classical studies on the thalamus. In the light of the most recent data it is here discussed that: a) the thalamus can subserve different functions according to functional changes in the cortical and subcortical afferent systems; b) the multifarious thalamic cellular entities play a crucial role in the different functional states.

Animals↗
PubMed2003

Kinaesthetic neurons in thalamus of humans with and without tremor.

Increased afferent input may alter receptive field sizes, properties and somatotopographic representation in the cortex. Changes in the motor thalamus may also occur as a result of altered afferent input. Such plasticity has been implicated in both sensory and movement disorders. Using tremor as a model of augmented afferent input to kinaesthetic/deep neurons representing the shaking limbs, we studied the representation and properties of these neurons in human thalamus in patients with resting tremor (RestTr) from Parkinson's disease, patients with action- or posture-induced tremor (ActionTr), and patients without tremor (NoTr). Data were collected during stereotactic thalamotomy or insertion of deep brain stimulators for relief of pain or movement disorder. Using microelectrode recording, 58 kinaesthetic neurons responding to wrist and/or elbow movement were studied by mapping the receptive field, carefully isolating each joint during testing. There were no significant differences in the proportions of single and multijoint responsive neurons in the different patient groups (RestTr, ActionTr and NoTr). The borders between tactile-cutaneous, deep-kinaesthetic and voluntary cell representations in the thalamus were mapped in 74 patients and compared between the different tremor groups. A significant difference in kinaesthetic representation was found: both the RestTr and ActionTr groups had a significantly greater kinaesthetic representation than the NoTr patients. There was an expansion of kinaesthetic representation in patients with chronic increased afferent drive from tremor, without alteration in RF size. No decrease in tactile representation was found, suggesting that the increase in kinaesthetic representation does not occur at the expense of tactile representation. These data suggest that plasticity can occur at the thalamic level in humans and may contribute to the pathogenesis of tremor.

Action Potentials↗
PubMed2005

The usefulness of fractional anisotropy maps in localization of lacunar infarctions in striatum, internal capsule and thalamus.

We aimed in this study to assess the clinical usefulness of fractional anisotropy (FA) maps in the evaluation of lacunar infarctions in striatum, internal capsule and thalamus. We retrospectively reviewed 28 patients (18 men, 10 women; mean age 63 years) who had acute lacunar infarction in striatum, internal capsule and thalamus on diffusion weighted MR imaging (DWI). Fractional anisotropy (FA) maps were generated in addition to conventional T2 weighted images (T2WI) and trace maps of DWI. Two radiologists reviewed the location of infarcts in combination with and without FA maps. Exact location of infarction was determined by FA maps, i.e. on the white band of internal capsule or outside the internal capsule. Accuracy and inter-observer agreement on determination of the location of infarction was evaluated. Accuracy of infarct localization by T2WI-DWI only was varied from 72 to 91% according to the observers. Inter-observer agreement value was moderate (Kappa=0.446), when images were interpreted by T2WI-DWI only. Clinical manifestation of each lesions were varied, but sensory motor stroke was mainly observed in thalamic lesion (50%), while pure motor hemiparesis was predominant in the case of infarct involving internal capsule, corona radiata (91%) and basal ganglia (83%). The FA map is useful in the evaluation of lacunar lesions in striatum, internal capsule and thalamus. Clinical presentation varies according to the exact location of lacunar infarctions, and more accurate diagnosis can be made by FA maps as well as conventional T2-weighted image and DWI.

Acute Disease↗
PubMed2001

The dorsal cyst in holoprosencephaly and the role of the thalamus in its formation.

The dorsal cyst is poorly understood, although it is commonly encountered in holoprosencephaly. We endeavor to establish the role of diencephalic malformations in the formation of the dorsal cyst and speculate on the developmental factors responsible. We reviewed the imaging of 70 patients with holoprosencephaly (MRI of 50 and high-quality CT of 20). The presence or absence of a dorsal cyst, thalamic noncleavage and abnormal thalamic orientation were assessed for statistical association, using Fisher's Exact Test and logistical regression. The presence of a dorsal cyst correlated strongly with the presence of noncleavage of the thalamus (P = 0.0007) and with its degree (P < 0.00005). There was a trend toward an association between abnormalities in the orientation of the thalamus and the dorsal cyst, but this was not statistically significant (P = 0.07). We speculate that the unseparated thalamus physically blocks egress of cerebrospinal fluid from the third ventricle, resulting in expansion of the posterodorsal portion of the ventricle to form the cyst.

Adolescent↗
PubMed1997

Differential distribution of the glutamate transporters GLT1 and rEAAC1 in rat cerebral cortex and thalamus: an in situ hybridization analysis.

The distributions in rat cerebral cortex and thalamus of the mRNAs encoding the glutamate transporters GLT1 and rEAAC1 (a rat homologue of rabbit EAAC1) were investigated by nonautoradiographic in situ hybridization using digoxigenin-labelled riboprobes. The probe recognizing rEAAC1 mRNA labelled exclusively neurons while GLT1 mRNA was found in glia as well as in select neuronal populations. The neurons containing the GLT1 transcript exhibited a distribution that was different from, and at some sites complementary to, the distribution of neurons containing rEAAC1 mRNA. In the subiculum, neurons positive for GLT1 and rEAAC1 were found in the deep and superficial part of the cell layer, respectively, while in the parietal neocortex GLT1 predominated in layer VI and rEAAC1 in layer V. Very few neuronal populations, most notably cells in hippocampal subfields CA3 and CA4, and in layer II in the entorhinal cortex, appeared to be equipped with both transcripts. In the thalamus the GLT1 labelling predominated in the midline and intralaminar nuclei while rEAAC1 labelling was found throughout this structure. It was concluded that the cerebral cortex and thalamus show cellular, laminar, as well as regional heterogeneities in the expression of the two glutamate transporters.

Amino Acid Transport System X-AG↗
PubMed2001

Chondroitin sulfate proteoglycans in the rat thalamus: expression during postnatal development and correlation with calcium-binding proteins in adults.

Postnatal expression of chondroitin sulfate proteoglycans was studied in the rat thalamus by immunocytochemistry and Western immunoblotting techniques with monoclonal antibodies that recognize carbohydrate epitopes (clones CS-56, 1-B-5, 2-B-6). The complex of the results shows that these antibodies recognize mostly nonoverlapping molecules whose expression is regulated during postnatal development. Chondroitin sulfate proteoglycans, recognized by antibody CS-56, and hyaluronan, identified by antibody 1-B-5 after hyaluronidase digestion, are abundant in the neuropil of most thalamic nuclei at the perinatal stage and progressively decrease during the second week of life, attaining levels barely detectable by immunocytochemistry at the end of the third week. In adult thalamus, chondroitin sulfate proteoglycans of high molecular mass, bearing glycosaminoglycans unsulfated in the linking region, and recognized by antibody 1-B-5 are confined to perineuronal nets around neurons chiefly localized in thalamic reticular nucleus. The immunoreactvity for antibody 2-B-6, specific for chondroitin-4-sulfate, is low at the perinatal stage and is not detectable in adult thalamus. Double-immunolabeling has shown that, along the rostrocaudal extension of reticular nucleus, the most developed perineuronal nets are associated with a subset of neurons expressing calretinin, and not with parvalbumin-positive neurons, which represent the largest neuronal population of the nucleus. The distribution of perineuronal nets supports the presence, in thalamic reticular nucleus, of neuronal subpopulations with different morphological and physiological features.

Animals↗
PubMed2003

Multiple deep-seated cavernomas in the third ventricle, hypothalamus and thalamus.

BACKGROUND: Cavernomas are rarely located in the third ventricle, hypothalamus, or thalamus. In this report, we present our experience managing a patient with three cavernomas, one each in the floor of the third ventricle, hypothalamus, and left thalamus. CASE PRESENTATION: This 62-year-old woman had had an unsteady gait and weakness of both legs for six months. Magnetic resonance imaging (MRI) revealed multiple intracranial tumours in the third ventricle, hypothalamus, and left thalamus. The third ventricle tumour was found to be a cavernoma by intra-operative endoscopic examination and then was excised via a transcortical, transventricular approach. Pathology revealed a cavernoma. The other two tumours were assumed to be cavernomas because of their MRI features. Three days after surgery, the patient developed right hemiparesis and disturbance of consciousness. Computed tomography revealed a left thalamic haemorrhage. After conservative treatment, her conscious level gradually recovered and she could walk with support seven months after surgery. INTERPRETATION: Our experience with this rare case of multiple, deep-seated cavernomas suggests that management of such patients requires specific consideration of the clinical manifestations, location, size, and previous bleeding history.

Brain Neoplasms↗
PubMed1981

A search for corticospinal collaterals to thalamus and mesencephalon by means of multiple retrograde fluorescent tracers in cat and rat.

An attempt has been made to determine anatomically whether in rat and cat cortical projections to ventrolateral nucleus of thalamus and to mesencephalon are in part composed of corticospinal collaterals. For this purpose two different fluorescent tracers were injected: one in the spinal cord and the other contralaterally in the lateral thalamus and in the mesencephalon respectively. In these experiments Fast Blue and True Blue were used in combination with Nuclear Yellow. Evans Blue was used in combination with Granular Blue. After injections of the tracers into the thalamus and spinal cord two different populations of single retrogradely labeled cortical neurons were found, while after injections in mesencephalon and spinal cord double-labeled cortical neurons occurred. This has lead to the conclusion that in cat and rat corticospinal neurons do not distribute collaterals to specific thalamic nuclei, but do distribute collaterals to mesencephalon. Moreover, the preferential distribution of the double-labeled corticospinal neurons in cat suggest that the corticospinal neurons distributing collaterals to the mesencephalon in part are concentrated in those cortical areas which subserve the steering of movements of the head, neck and trunk.

Animals↗
PubMed1987

Response properties of spinal neurons projecting to midbrain or midbrain-thalamus in the monkey.

Response and receptive field properties were determined for 24 spinal neurons backfired from midbrain or midbrain-thalamus in the anesthetized monkey. Recording sites were located in laminae I (11 cells), IV (6), V (6) and VI (1) in the lumbosacral spinal cord. The mean axonal conduction velocity of cells projecting to midbrain was significantly less than that of cells projecting to midbrain-thalamus. Cells backfired only from midbrain had complex excitatory receptive fields whereas those projecting to midbrain-thalamus had excitatory receptive fields confined to a single limb. Cells in both populations had complex inhibitory receptive fields.

Animals↗
PubMed1990

Topographic distribution of pallidal neurons projecting to the thalamus in macaques.

The respective topographic distribution of the pallidal neurons projecting to the central complex (centre médian-parafascicular complex) and to the oral part of the lateral mass of the thalamus was studied by using a topographic technique based on ventricular landmarks. WGA-HRP was stereotactically injected into the central complex of 4 macaques and into the oral part of the lateral mass of the thalamus of 3 others. Neurons projecting to the central complex were located in the caudal, lateral and ventral region of the ipsilateral medial nucleus of the pallidum. Pallidal neurons projecting to the lateral mass of the thalamus were more numerous and occupied the entire volume of the medial pallidum apart from a small rostral and dorsomedial region. The location of the pallido-central complex neurons appeared to be included in that of the neurons projecting to the lateral mass. As very few neurons of this shared region were unlabeled, it is very likely that the same pallidal neurons project to both targets. The pallido-central complex neurons were located in the region crossed by axons coming from the putaminal sensorimotor territory of the striatum. These results provide further evidence that Nauta and Mehler's loop is a real closed loop probably involved in sensorimotor processing.

Animals↗
PubMed1992

Effect of superior colliculus lesions on sensory unit responses in the intralaminar thalamus of the rat.

The effects of kainic acid lesions of the intermediate and deep layers of the superior colliculus on the sensory input to the intralaminar thalamus of the rat were determined. Ipsiversive circling and contralateral sensory neglect were consistently seen after lesion placement. Two to 7 days later, the intralaminar thalamus was systematically explored for extracellular mechanoreceptive unit responses to high threshold and low threshold stimuli. On the side ipsilateral to the lesion the number of responsive units was reduced by 51%. The loss was particularly marked for nociceptive units (80%), and low threshold and complex units with orofacial receptive fields (73%). This effect may involve a partial deafferentation of the intralaminar thalamus as well as altered excitatory thresholds of thalamic neurons. It is suggested that the functionally distinct direct tectothalamic projection as well as the indirect tecto-reticulo-thalamic pathway are implicated.

Animals↗