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At least 1,675 records · Page 93Linked to original sources
PubMed1984

The ventral pallidal projection to the mediodorsal thalamus: a study with fluorescent retrograde tracers and immunohistofluorescence.

We have examined rat basal forebrain projections to the mediodorsal thalamic nucleus (MD) by making injections of retrogradely transported fluorescent tracers into the MD. Additionally, in some animals, we also stained sections for glutamate decarboxylase (GAD) by the indirect fluorescent antibody technique. Our results demonstrate that the following basal forebrain areas project to the MD: lateral orbital cortex, agranular insular cortex superficial to claustrum, primary olfactory cortex, diagonal band nuclei, ventral pallidum, and amygdala. A large number of labeled cells are present in the olfactory tubercle, and these cells are almost without exception located in dense GAD-positive ventral pallidal areas rather than in striatal regions of the tubercle. This ventral pallidal projection to the MD strengthens the concept of a ventral striatal-pallidal system in parallel to the classic striatal-pallidal system which projects to the ventral thalamus. These results are also discussed in relationship to the olfactory system.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMedDate not supplied

[Effect of sectioning the mammillothalamic tract on neurons of limbic nuclei of the thalamus].

Neuronal activity of n. AV (n = 75) and n. AD (n = 55) of the thalamus was recorded extracellularly in unanaesthetized chronic rabbits after complete transection of the mammillo -thalamic tract (MTT). Elimination of this powerful afferent system produced a surprisingly small effect upon spontaneous and evoked neuronal activity. All types of responses were preserved in both nuclei, though some increase of multimodal diffuse tonic responses and decrease of more specialized phasic and complex on-effects occurred in n. AV. In both nuclei short-latency responses (less than 14 ms) to auditory stimuli disappeared. The number of units with dynamic transformations of responses during repeated stimuli application (gradual emergence and shaping of responses, as well as their habituation) decreased 2-3-fold in both nuclei. The impulse activity travelling in MTT seems to be not critical for limbic nuclei sensory reactivity but significant for plasticity of the responses.

Animals↗
PubMed1984

[Connections of the laterodorsal nucleus of the thalamus in the monkey. Study of efferents].

Efferent pathways of the LD nucleus of the thalamus were studied in 6 Papio-papio baboons with the retrograde transport technique utilizing HRP. Injections were made in cingular and parietal cortex and hippocampal formation. Large projection from the LD to the cingular and subicular cortex were visualized as reciprocal connections. No pathway to parietal area 7 was found. The course of the fibers is via the fornix, the cingular bundle and the retro-lenticular portion of the internal capsule. The result of this study make it necessary to reconsider neuropathological hypotheses on memory.

Animals↗
PubMedDate not supplied

[Spike activity of neurons of the medial thalamus of the rat during urethane anesthesia, wakefulness and immobilization stress].

A statistical analysis was carried out of unit activity in the medial thalamus (MT) of rats in states of urethane anaesthesia, quiet unrestrained wakefulness and immobilization stress. Discharge activity of MT neurones in these states significantly differed by parameters characterizing both single cells (mean frequency, standard deviation, variation coefficient) and their populations (intragroup variability of parameters, homogeneity of population as to the activity of its cells components, the extent of connections between them). The revealed differences are interpreted as a reflection of the properties of central interneuronal integration created in accordance with real needs of the organism for providing for its adaptive activity.

Anesthesia, General↗
PubMedDate not supplied

[Effect of stimulation of the mediodorsal nucleus of the thalamus on the synchronous flow of cortical electrical processes].

It was shown in chronic experiments on rabbits that stimulation of the mediodorsal thalamic nucleus brings about, as a rule, en enhancement of amplitudes of the spatially-synchronous cortical theta-rhythm and a decreased frequency of its oscillations. Analysis of the phenomenon by means of a simple mathematical models shows that such a connection between amplitude and frequency EEG parameters may be accounted for by the existence of two-way cyclic interactions between the cortex and the thalamus, forming a closed contour of a feedback connection. The capacity of the mediodorsal thalamic nucleus to influence the synchroneity of cortical electrical processes is compared with published data on its role in conditioned activity.

Animals↗
PubMed1983

[Causes and effects of synthesis differences of the dorsomedial nucleus of the thalamus].

Attention has been paid to the connection between morphogenesis and the synthesis of tissue structures with regard to their effects upon the functions and, on the other hand, their dependence on diseases and changes in blood circulation. A synthetic interpretation of the brain leads to the picture of a total ("ganzheitlich") order which, by itself, helps to explain the existence of a harmony. We have pointed to limitations in drawing parallels (in a biological sense) between human beings and animals. Above all, this becomes clear in the case of the Ncl. medio-dorsalis of the thalamus: Here is a functional system, the importance of which (for psycho-pathological conditions and disturbances) can be observed. Thereby, lacks of functions that are due to the dynamics of vital processes, can be explained. "Functional morphae" (Gestalten) are only those that are of a certain use. The variability of the building elements of the Ncl. medio-dorsalis is greater than its functions would require. However, there may be border-line cases, being explicable as a result of micro-evolution. The "change of forms" ("Formwandel") can finally help to illustrate certain pathological formations whose detailed interpretation is not entirely possible.

Adult↗
PubMed1983

Organization of the visual thalamus: corticothalamic projections from the primary visual area in the opossum.

The projections from the visual cortex to thalamic nuclei in the opossum were investigated by degeneration and radioautographic methods. Efferent axons from the striate cortex course from the internal capsule to the thalamus in two bundles, one of which innervates the reticular and dorsal lateral geniculate nuclei, while the other bundle innervates the external layer of the ventral lateral geniculate nucleus. Both bundles course along and through terminal fields found in the lateral posterior nucleus. The visuotopic organization inferred from the corticofugal pathway shows that projection lines in the dorsal lateral geniculate nucleus (DLGN) run along medio-lateral strips including both the beta and alpha segments, across the quasi-laminae of retino-geniculate projection, and that naso-temporal axes in the visual field run in a dorso-ventral direction through the DLGN. The external layer of the ventral lateral geniculate nucleus receives a projection from the striate cortex and bilateral projections from the retina, and naso-temporal axes in the visual field are represented along a dorso-ventral direction in this layer. The striate cortical projections cover approximately the lateral two-thirds of the lateral posterior nucleus, overlapping a small retinal terminal field, and naso-temporal axes in the visual field are represented onto the cortico-recipient zone in a mirror-symmetric direction to that of the adjoining DLGN. In all these three cortico-recipient zones, dorso-ventral axes in the visual field are represented in a rostro-caudal direction.

Animals↗
PubMed1984

[Morphophysiologic study of the afferent projections of the posterolateral nucleus of the thalamus in the rat].

Afferent connections of the posterolateral nucleus of the thalamus were studied in rat using retrograde axonal transport of horseradish peroxidase. It was shown that the posterolateral nucleus receives ascending projections from SC, GL, PT, VP, VL, zona incerta and hypothalamus as well as descending projections from cortical areas 18A, 20, 18, 7, 29c , 17 and 36 and from fascia dentata of rippocampus as well. In electrophysiological experiments 134 from 229 investigated neurons of the posterolateral nucleus responded to isolated or simultaneous visual, auditory and cutaneous stimulations. 53 neurons were monosensory units; they responded only to visual (41/53) or cutaneous (12/53) stimulation. Cells responding only to auditory stimulation were not found. Polysensory neurons (81/134) showed convergence of signals from two-three sensory systems and received preferential inputs from visual and somatosensory systems. The polysensory cells showed nonlinear interaction between responses during heterosensory stimulations.

Afferent Pathways↗
PubMed1983

[Characteristics of the evoked electrical reactions of the nucleus lateralis posterior in the rabbit thalamus and their dependence on cortical and reticular formation function].

The electrical responses of n. lateralis posterior of the thalamus (nLP) to light stimuli of different intensity were recorded in alert rabbits, and their interrelationships with the reactions of retina, superior colliculi and visual cortex were analysed. The retina rather than superior colliculi appeared to play a major role in afferent supply of nLP in rabbit. The organized mechanism of facilitating reticular control of the nLP function was shown, with the adrenoreactive mechanism playing the most important role in the reticular influence. The inhibitory influence of visual and sensomotor cortical areas upon neuronal mechanism of nLP forming the responses to photostimuli, was revealed. The effects of visual cortex were the most expressive and stable.

Animals↗
PubMed1981

[Mass extracellular monosynaptic potential of synapses of a single axon in the optic thalamus of frogs upon electric stimulation of the retina].

Mass extracellular monosynaptic PSP of one axon synapses ("EEG quantum") were reliable recorded in the frog thalamus as "all-or-none" potentials up to 250 muV at threshold electrical stimulation of the retina. The degree of facilitation of the second response was measured during paired-pulse stimulation. The ratio of the testing PSP amplitude to the conditioning one dependent on the signal amplitude. The ratio reached 250% at interstimulus interval of 5 ms with amplitude of conditioning PSP being about 50 muV.

Animals↗
PubMed1980

[Descending connections between the parafascicular complex of the thalamus and midbrain periaqueductal gray].

Descendin projections of the parafascicular complex (CM--Pf) of the cat thalamus to periaqueductal gray matter (PAG) of the midbrain were studied by Fink-Heimer electrocoagulation of CM--Pf complex in stereotaxic coordination. Degenerative changes in nerve fibers were most pronounced on transversal sections of the brain stem in the lateral nucleus of PAG, whereas less degeneration was seen in the ventral part of the medial nucleus.

Animals↗
PubMed1993

[Substance P is not involved in SII descending modulation of the nucleus centrum medianum of the thalamus in cats].

It was investigated that the effects of electrical stimulation of the somatosensory area II (SII) of the cerebral cortex and electroacupuncture on substance P (SP) concentration in the perfusate from the nucleus centrum medianum (CM) of the thalamus, in order to probe into if SP participates in the SII descending modulation of the nucleus CM and this mechanism of acupuncture analgesia. Adult cats were randomly divided into three groups: control, electroacupuncture and electrical stimulation of SII. Push-pull perfusion technique was used to collect the perfusate from the nucleus CM. SP contents in the perfusate were determined by radioimmunoassay. The results showed that SP contents in the perfusate have not statistically significant changes before and after the electrical stimulation of SII or electroacupuncture, suggesting that the SP release from the nucleus CM was not influenced by the stimulation of SII or electroacupuncture. It is indicated that SP may not associate with the SII descending modulation of the nucleus CM and this mechanism of acupuncture analgesia.

Acupuncture Analgesia↗
PubMed1994

Distribution and response evoked by microstimulation of thalamus nuclei in patients with dystonia and tremor.

The effect of 806 microstimulations were observed in 16 patients with movement disorders, dystonia (DA, n = 6) and tremor (TR, n = 10). Among the 347 sites in DA patients motor response was seen at 29 sites, the response with increased dystonia was seen at 28 sites. The effect could be seen at 14 sites (50%) in ventrointermedialis (Vim), five sites (18%) in ventrocaudalis (Vc) and five sites (18%) in white matter (Wm). As for the other four sites, one site was in ventraloralis anterior (Voa), two sites in ventraloralis posterior (Vop), and one site in dorsal thalamus (dth), but reduction of dystonia drive was only seen at one site in dth. On the other hand, among the 459 sites in TR patients, motor response leading to reduction of tremor drive was seen at 38 sites, of which 30 sites (79%) were noted in Vim nuclei, and five sites (13.2%) in vc nuclei; of the remaining sites, two were seen in Vop nuclei, one in dth, and no increasing tremor drive was observed in all area. In general, paresthesia was the most common response, which was found at 159 sites (45.8%) with DA and 216 sites (47.1%) with TR. Pain was only seen at one site in Wm of DA; warm/cold and vertigo could be seen in Vop, Vim, and vc nucleus respectively. No responses were shown at 156 sites (45%) in DA, and 201 sites (43.8%) in TR.

Dystonia↗
PubMed1975

[Connections between the nucleus lateralis dorsalis of the thalamus and the limbic system in man. Study of 12 anatomo-clinical cases of vascular origin].

Lateralis dorsalis nucleus of thalamus belong to the limbic system of Papez more by its trigonal than cingular afferent pathways. Its parietal efferent pathways are probable, its cingular and trigonal ones possible but not proved. Neuropathologic studies provide informations to separate a latero-ventral part connected with parietal cortex and a mediodorsal part connected with limbic system.

Aged↗
PubMed1994

Spatiotemporal structure of somatosensory responses of many-neuron ensembles in the rat ventral posterior medial nucleus of the thalamus.

Classically, the rat ventral posterior medial (VPM) nucleus of the thalamus has been considered as a simple passive relay for single-whisker information to the primary somatosensory cortex (SI). However, recent reports have suggested that the VPM could contain a much more coarsely coded and spatiotemporally complex representation of the rat whisker pad. To address this possibility properly, we have carried out chronic simultaneous recordings of large numbers (up to 23) of single neurons, distributed across the entire VPM, in both awake and lightly anesthetized adult rats. Quantitative, computer-based reconstruction of receptive fields (RFs) revealed that single VPM neurons exhibit significant responses to discrete stimulation of as many as 20 single whiskers (mean +/- SD RF size, 13.7 +/- 4.8 whiskers). By defining multiple response magnitude (RM) thresholds it was possible to subdivide these large VPM RFs quantitatively into a prominent center (mean +/- SD, 1.41 +/- 0.70 whiskers, RM > 95%) and an excitatory surround (up to 18 whiskers, RM < 95%). VPM neurons exhibited both short-latency responses (SLRs, from 4 to 10 msec poststimulus) and/or long-latency responses (LLRs, 15-25 msec), each followed by inhibitory responses. Though LLRs were weaker (mean +/- SD, 47.19 +/- 33.34 Hz) than SLRs (119.63 +/- 50.12 Hz), they often defined RFs that differed considerably from those defined by the SLRs of the same cell. In particular, VPM cells with short-latency RFs centered in caudal whiskers (e.g., C1, D1, E1) showed a poststimulus time-dependent shift of these RF centers toward the rostral whiskers (e.g., C4, D4, E4). These caudal-to-rostral (C-->RF shifts occurred in neurons with the largest RFs of our sample (17.2 +/- 2.4 whiskers). On the other hand, VPM cells with short-latency RFs centered in rostral whiskers had the smallest RFs (13.1 +/- 4.1 whiskers) and usually did not exhibit time-dependent RF center shifts. Multivariate analysis revealed that these two groups of VPM neurons, C-->R shifting and rostral position (RP) cells, could be statistically distinguished according to a combination of three RF attributes (short-latency RF center location, RF size, and magnitude of RF center shift). Quantitative, computer-based reconstruction of "population response maps" demonstrated that the "place" coding for each single whisker in the VPM involved a distinct weighted contribution from a large proportion of the simultaneously recorded neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Anesthesia↗
PubMed1993

Directionally selective mnemonic properties of neurons in the lateral dorsal nucleus of the thalamus of rats.

The hippocampal formation has been extensively studied for its special role in visual spatial learning and navigation. To ascertain the nature of the associations made, or computations performed, by hippocampus, it is important to delineate the functional contributions of its afferents. Therefore, single units were recorded in the lateral dorsal nucleus of the thalamus (LDN) as rats performed multiple trials on a radial maze. Many LDN neurons selectively discharged when an animal's head was aligned along particular directions in space, irrespective of its location in the test room. These direction-sensitive cells were localized to the dorsal aspect of the caudal two-thirds of the LDN, the site of innervation by retinal recipient pretectal and intermediate/deep-layer superior colliculus cells (Thompson and Robertson, 1987b). The directional specificity and preference of LDN cells were disrupted if rats were placed on the maze in darkness. If the room light was then turned on, the original preference was restored. If the light was again turned off, directional firing was maintained briefly. Normal directional firing lasted about 2-3 min. After this time, the directional preference (but not specificity) appeared to "rotate" systematically in either the clockwise or counterclockwise direction. The duration of normal directional discharge patterns in darkness could be extended to 30 min by varying the behavior of the animal. LDN cells required visual input to initialize reliable directional firing. After the rat viewed the environment, directional specificity was maintained in the absence of visual cues. Maximal directional firing was achieved only when the rat viewed the entire test room, and not just the scene associated with the directional preference of the cell. Thus, contextual information seems important. Also, a significant correlation was found between directional specificity and errors made on the maze during acquisition of the task. It was concluded that the LDN may pass on to the hippocampal formation directional information that is not merely a reflection of current sensory input. As such, the LDN may serve an important integrative function for limbic spatial learning systems.

Animals↗
PubMed1993

Effective response evoked by microstimulation of thalamus nuclei in patients with tremor.

459 microstimulations were done in 10 patients with tremor. The motor evoked response with reduction tremor drive was observed at 38 sites, of which 30 (79%) were noted in ventrointermedialis (vim) nuclei, and 5 (13.2%) in ventrocaudalis (vc) nuclei, 2 in ventroralis posterior (vop) nuclei, 1 in dorsal thalamus (dth). No increased tremor drive response was noted in all the sites. Paresthesia was the most common response (47.1%). Except pain at 1 site in vc nuclei, warm/cold and vertigo were noted in vop, vim, vc nuclei. No responses accounted for 43.8%.

Electric Stimulation↗
PubMed1977

[Electron-autoradiographic analysis of projections of somatosensory cortex regions I and II to the posterior ventral nucleus of the thalamus].

To reveal the differences in the nucleus ventralis postero-lateralis (VPL) of the thalamus of the corticofugal fibers originating from the first (S1) and the second (S2) somatosensory areas a combined morphological study was undertaken using autoradiography and electron microscopy of the degenerating terminals. Within the range of VPL distribution of the cortico-fugal fibers of the corresponding zones of two cortical somatosensory regions differed from one another. The terminals of both types of the fibers established synaptic contacts, chiefly with the distal dendrites of the relay VPL cells, and much more rarely with the dendrites of the interneurons of the Golgi II type. No direct convergence of the fibers originating from two somatosensory regions on single VPL elements was observed.

Animals↗