Anatomical observations on the dorsal column nuclei, their thalamic projection and the cytoarchitecture of some somatosensory thalamic nuclei in the monkey.
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Neuronal and synaptic structure of the specific thalamic nuclei.
1. Neuronal organization of the specific thalamic nuclei is rather uniform. The ratio of thalamocortical relay neuron and Golgi II type interneuron is 2:1, as well as 3:1. 2. Interneurons show GABA-immunoreactivity. The presynaptic dendrites (F2-profiles) modify the intrathalamic transmission of the specific afferent impulses. 3. The two principal types of synaptic arrangements were observed in the specific thalamic nuclei: the synaptic glomeruli and the general neuropil. 4. Three different types of axon-terminals could be distinguished in the neuropil of all specific thalamic nuclei: the large RL-boutons are terminals of the specific afferents, the small RS-boutons are mainly the terminals of cortical afferents and the F1-boutons are probably axon-terminals of the Golgi II type interneurons, as well as axon-endings originating from the reticular nucleus of thalamus. 5. Synaptic contacts of the specific afferent fibers have basic importance in the relay nuclei. 6. In associative and anterior thalamic nuclei the RS- and F1-boutons have a significant modification effect on the interneurons (inhibition-disinhibition).
Animals↗
Topographic organization of subcortical projections to the anterior thalamic nuclei in the rat.
Subcortical projections to the anterior thalamic nuclei were studied in the rat, with special reference to projections from the mammillary nuclei, by retrograde and anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase. The medial mammillary nucleus (MM) projects predominantly ipsilaterally to the entire anterior thalamic nuclei, whereas the lateral mammillary nucleus projects bilaterally to the anterodorsal nucleus (AD) of the anterior thalamic nuclei. A topographic relationship was recognized between the MM and the anterior thalamic nuclei. The dorsal region of the pars mediana of the MM projects to the interanteromedial nucleus (IAM), whereas the ventral region projects to the rostral part of the anteromedial nucleus (AM). The dorsal and the ventral regions of the pars medialis project to the dorsomedial part of the AM at its caudal and rostral levels, respectively. The dorsomedial region of the pars lateralis projects to the ventral AM. The ventrolateral region of the pars lateralis projects to the ventral part of the anteroventral nucleus (AV) in such a manner that rostral cells project rostrally and caudal cells project caudally. The pars basalis projects predominantly ipsilaterally to the dorsolateral AV and bilaterally to the AD. The rostrolateral region of the pars posterior projects to the lateral AV, whereas the medial and the caudal regions of the pars posterior project to the dorsomedial AV. The rostrodorsal part of the nucleus reticularis thalami was found to project to the anterior thalamic nuclei; cells located rostrally in this part project to the IAM and AM, whereas cells located caudodorsally project to the AV and AD. The laterodorsal tegmental nucleus projects predominantly ipsilaterally to the AV, especially to its dorsolateral part. The present study demonstrates that subdivisions of the subcortical structures are connected to the subnuclei of the anterior thalamic nuclei, with a clear-cut topography arranged in the dorsoventral and the rostrocaudal dimensions.
Animals↗
Restricted cortical termination fields of the midline and intralaminar thalamic nuclei in the rat.
The projections from the midline and intralaminar thalamic nuclei to the cerebral cortex were studied in the rat by means of anterograde tracing with Phaseolus vulgaris-leucoagglutinin. The midline and intralaminar nuclear complex taken as a whole projects to widespread, predominantly frontal, cortical areas. Each of the constituent thalamic nuclei has a restricted cortical projection field that overlaps only slightly with the projection fields of adjacent midline and intralaminar nuclei. The projections of the intralaminar nuclei cover a larger cortical area than those of the midline nuclei. The laminar distributions of fibres from individual midline and intralaminar thalamic nuclei are different and include both deep and superficial cortical layers. The parataenial, paraventricular and intermediodorsal midline nuclei each project to circumscribed parts of the prefrontal cortex and the hippocampal and parahippocampal regions. In the prefrontal cortex, the projections are restricted to the medial orbital, infralimbic, ventral prelimbic and agranular insular fields, and the rostral part of the ventral anterior cingular cortex. In contrast to the other midline nuclei, the rhomboid nucleus projects to widespread cortical areas. The rostral intralaminar nuclei innervate dorsal parts of the prefrontal cortex, i.e. the dorsal parts of the prelimbic, anterior cingular and dorsal agranular insular cortical fields, the lateral and ventrolateral orbital areas, and the caudal part of the ventral anterior cingular cortex. Additional projections are aimed at the agranular fields of the motor cortex and the caudal part of the parietal cortex. The lateral part of the parafascicular nucleus sends fibres predominantly to the lateral agranular field of the motor cortex and the rostral part of the parietal cortex. The medial part of the parafascicular nucleus projects rather sparsely to the dorsal part of the prelimbic cortex, the anterior cingular cortex and the medial agranular field of the motor cortex. Individual midline and intralaminar thalamic nuclei are thus in a position to directly influence circumscribed areas of the cerebral cortex. In combination with previously reported data on the organization of the midline and intralaminar thalamostriatal projections and the prefrontal corticostriatal projections the present results suggest a high degree of differentiation in the convergence of thalamic and cortical afferent fibres in the striatum. Each of the recently described parallel basal ganglia-thalamocortical circuits can thus be expanded to include projections at both the cortical and striatal levels from a specific part of the midline and intralaminar nuclear complex. The distinctive laminar distributions of the fibres originating from the different nuclei emphasize the specificity of the midline and intralaminar thalamocortical projections.
Animals↗
Inhibition of gonadotropin secretion induced by stimulation of thalamic nuclei.
The effect of electrochemical stimulation (anodic current, 100 micronA/30 sec) of thalamic nuclei was studied in nonanesthetized freely-behaving rats bearing chronic implanted electrodes and plastic cannulae inserted into the jugular vein for blood sampling. Stimulation of the anterior thalamic nuclei, the nucleus (n.) mediodorsalis thalami (MD) and the n. posteromedianus thalami at 2 p.m. on the day of proestrus prevented spontaneous ovulation and the release of LH which takes place on that day. No effect on ovulation or LH release was observed after stimulation of the n. lateralis thalami, the n. ventralis thalami or other thalamic nuclei or after passing a cathodic current through the n. MD. Stimulation of the n. MD resulted also in a significant decrease of the elevated serum LH levels found after an injection of progesterone into ovariectomyzed estrogen-primed rats. These results indicate that nuclei of the medial thalamic region are capable of inhibiting LH secretion. No stimulatory influence of LH release was observed after thalamic stimulation in ovariectomized estrogen-treated rats.
Animals↗
VEP and SEP in non-specific thalamic nuclei and pulvinar during stereotaxic surgery.
This report is based on recordings of evoked photic (VEP) and somatosensory response (SEP) from the thalamic nuclei and cortex of 17 humans during stereotaxic surgery. The cortical SEP and VEP have relatively uniform patterns. The initial latency of the cortical VEP is shorter than that of SEP. Both thalamic SEP and VEP give relatively constant response to Limitans and Parafascicularis, Centromedian and Pulvinar but Dorsomedial nucleus has a smaller and variable latency. Thalamic SEP gives a better response than thalamic VEP in Nucleus Limitans and Parafascicularis, Nucleus Centromedian, and Pulvinar. This suggests that the non-specific thalamic nuclei, especially Centromedian, Limitans and the nucleus Parafascicularis and Pulvinar, play an important role in pain conduction and function as a relay station in the transmission of non-specific visual impulses. The visual evoked response pattern as well as somato-sensory evoked response from the thalamic nuclei can serve as a very reliable means of controlling the target area prior to subcortical destruction.
Adult↗
[Projections of different areas of the putamen on tha thalamic nuclei].
In the work presented the projections of rostral and caudal areas of the putamen on the thalamic nuclei were studied. The analysis of the frontal serial sections from the cat brains impregnated according to the methods of Nauta-Gygax, Finck-Haimer, Wiitanen made it possible to state that all the areas of the putamen radiate a great number of axons to the lateral thalamic nuclei--ventro-anterior, ventro-lateral, lateral-posterior, and ventro-posterior-medial. Only the rostral area of the putamen sends a mass of fibres to the nuclei of the median thalamus--medial-dorsal, central, central-lateral and ventro-posterior-lateral. On the other hand, in the posterior thalamic nucleus a great number of axons only from caudal area of the putamen have their terminals.
Animals↗
Two types of epileptic cortical after-discharges evoked by the stimulation of the hippocampus and thalamic nuclei in rats.
Rhythmic cortical phenomena were evoked by stimulation of hippocampus and/or thalamus in rats. Electrical stimulation of thalamic nuclei (nc. ventralis dorsomedialis VDM and nc. lateralis anterior--LA) by single pulses elicited rhythmic after-discharge ("spindle") as a late component of the cortical response, whereas identical stimulation of hippocampus did not trigger such an activity. Rhythmic stimulation of thalamic nuclei elicited cortical incremental responses more often than stimulation of hippocampus. Epileptic self-sustained after-discharges (AD) occurred after the endo of rhythmic stimulation in 66% of hippocampal stimulations, in 35% of VDM stimulations and in 30% of LA stimulations. AD evoked by stimulation of the hippocampus (long duration discharges of slow serrated waves) differed characteristically from AD following stimulation of the VMD (short duration spike and wave complexes). Stimulation of the LA in half of the cases led to the "hippocampal" pattern of serrated wave after-discharges, in the remaining cases spike-and-wave complexes or a combined AD pattern was recorded.
Animals↗
Single units activities in ventral posterior and posterior group thalamic nuclei during nociceptive and non nociceptive stimulations in the cat.
The purpose of this study was to define, in hyperventilated and unanesthetized cats, the role of the posterior thalamic nuclei in pain mechanisms. Unit activities of these structures were compared to those of the ventro-posterior nucleus during non-noxious (touch, brushing) and noxious stimulations (pinches and intra-arterial injections of bradykinin into the limbs). 135 cells with somatic inputs and clear peripheral excitatory receptive field were studied. The cells driven by noxious stimulations were located in the posterior group nuclei as anatomically defined by Rinvik. These units, preferentially excited from contralateral receptive fields, were localized in POm, POl, suprageniculate nuclei, the magnocellular division of the medial geniculate body (Mgmc) and the ventral part of the lateral posterior nucleus. At this level two groups of units were found: those driven only by noxious stimulations and those driven by both noxious and non-noxious stimulations. On contrast, cells recorded at the levels of the VPm and VPl were not activated by noxious stimuli. These results emphasize the role of the posterior thalamic nuclei in pain processing.
Animals↗
Spontaneous neuronal hyperactivity in the medial and intralaminar thalamic nuclei of patients with deafferentation pain.
Electrical activity was recorded from single cells in the thalamus of 10 patients with chronic pain associated with deafferentation. Under local anesthesia, these patients underwent either electrode implantation or thalamotomy for treatment of their pain. In eight of the 10 patients, single units were identified as discharging spontaneously in high-frequency, often rhythmic, bursts. The discharges were of two types: short bursts comprised of two to six spikes with a burst frequency of one to four per second; and long trains of 30 to 80 spikes of similar frequency. Reconstruction of electrode trajectories indicated that recordings were made from the region corresponding to the lateral aspect of the mediodorsal thalamic nucleus, the central lateral nucleus, a small part of the central median nucleus, and the parafascicular nucleus. In the eight patients in whom spontaneous neuronal burst activity was exhibited, it was impossible to study activity evoked by natural cutaneous stimulation due to the continuous spontaneous neuronal discharges. Both animal and human studies have suggested that pain related to deafferentation is accompanied by spontaneous hyperactivity in the dorsal horn of the spinal cord and in the ventral posterior thalamic nuclei. The authors present evidence of spontaneous neuronal hyperactivity in the intralaminar thalamic nuclei of patients with pain related to deafferentation. The findings suggest that spontaneous neuronal discharge in patients with pain related to deafferentation is more widespread in the central nervous system than has been previously appreciated. The results have important implications for the surgical treatment of chronic pain.
Afferent Pathways↗
Cortical projections of the anterior thalamic nuclei in the cat.
Unilateral stereotaxic lesions were made in the anterior thalamic nuclei of the cat, and the ensuing terminal degeneration traced to the medial cortex by the methods of Nauta-Gygax and Fink-Heimer. The anterodorsal nucleus projects to the retrosplenial, postsubicular and presubicular areas. These projections appear to be organized in the dorsoventral direction. The posterior portion of the retrosplenial area receives no fibers from the anterodorsal nucleus. Fibers from this nucleus are distributed largely in layer I and in layer III and the deep portion of layer II of the posterior limbic cortex. The anteroventral nucleus sends fibers to the cingular area and parts of the retrosplenial, postsubicular and presubicular areas. These projections appear to be organized in a topical manner mediolaterally. When the lesion involves the parvocellular part of the nucleus, degeneration spreads to the lower lip, bank and fundus of the splenial sulcus. There appears to be an anteroposterior organization in the cortical projections of the anteroventral nucleus. Fibers from the anteroventral nucleus are distributed most profusely in layers IV and III and in the superficial portion of layer I of the posterior limbic cortex. The anteromedial nucleus sends fine fibers to the anterior limbic region and to the cingular, retrosplenial, postsubicular and presubicular areas. The cortical projections of the anteromedial nucleus appear to be topographically organized in the dorsoventral direction. Fibers from the anteromedial nucleus are distributed largely in cortical layers V and VI of the anterior and posterior limbic regions.
Animals↗
An autoradiographic study of cortical projections from motor thalamic nuclei in the macaque monkey.
The special areal and laminar distributions of cortical afferent connections from various thalamic nuclei in the monkey (Macaca fuscata) were studied by using the anterograde axonal transport technique of autoradiography. The following findings were obtained. The superficial thalamocortical (T-C) projections, terminating in the (superficial half of) cortical layer I, arise mainly from the nucleus ventralis anterior, pars principalis (VApc) and nucleus ventralis lateralis, pars oralis (VLo), and possibly from the nucleus ventralis lateralis, pars medialis (VLm) and nucleus ventralis anterior, pars magnocellularis (VAmc). The VApc gives rise to the superficial T-C and deep T-C projections onto the postarcuate premotor area around the arcuate genu and spur, and onto the dorsomedial part of the caudal premotor area as well as the supplementary motor area (SMA). The VApc also gives rise to only deep T-C projections onto the remaining premotor area and onto the rostral bank of the arcuate sulcus as well as the ventral bank of the cingulate sulcus at the level of the premotor area. The VLo gives rise to the superficial T-C projections onto the ventrolateral part of the motor area (mainly to the forelimb motor area) and onto the dorsomedial part to the mesial cortex at the rostral level of the motor area. The VAmc gives rise to the superficial T-C projections onto the banks of the arcuate genu and adjacent region of area 8. Area X, the nucleus ventralis posterolateralis, pars oralis (VPLo), nucleus ventralis posterolateralis, pars caudalis (VPLc), nucleus ventralis posteromedialis (VPM) and possibly the nucleus ventralis lateralis, pars caudalis (VLc) send only deep T-C projections. The dorsal and medial parts of the VLc project onto the premotor area, the rostral part of the motor area and the SMA, and also the ventral bank of the cingulate sulcus. Area X projects onto the premotor area, the SMA, and the caudal part of area 8. The thalamic relay nuclei projecting onto the frontal association cortex were found to be the VAmc, medial VLc and area X.
Afferent Pathways↗
[Responses of the reticular nucleus neurons and dorsal thalamic nuclei neurons in the cat during extinction of a conditioned instrumental reflex].
Activity of 66 neurons of the reticular nucleus (R), 31 neurons of the ventroposterolateral nucleus and 14 neurons of the posterolateral nucleus-pulvinar complex of the thalamus was investigated during extinction of the conditioned instrumental alimentary reflex. The quantity of R neurons that show initial excitation in response to the conditional stimulus in the first 300 ms decreased during extinction. Conditioned placing reactions and late excitatory and inhibitory neuronal responses in the R and dorsal thalamic nuclei with latency above 300 ms disappeared during extinction simultaneously. The background unit activity decreased during extinction in the 2/3 of investigated neurons of R and dorsal thalamic nuclei. It is suggested that the efferent influence from the R decreased during extinction.
Animals↗
Epileptiform EEG activity of the centromedian thalamic nuclei in children with intractable generalized seizures of the Lennox-Gastaut syndrome.
Centromedian thalamic nuclei (CM) epileptiform EEG activities were recorded in children with intractable generalized seizures of Lennox-Gastaut syndrome (LGS) through implanted recording-stimulating electrodes used for seizure control. Ictal CM epileptiform activities were consistently correlated to widespread surface cortical EEG activities and symptoms in all patients and all types of generalized seizures; i.e., fast spike discharges at CM correlated at onset of tonic and tonic-clonic generalized seizures; slow (1-2 Hz) spike-wave complex discharges at CM correlated for atypical absence seizures; slow polyspike-wave complex discharges correlated for myoclonic seizures; and spike bursts and suppression patterns correlated for combined tonic-atonic-myoclonic seizures. Ictal EEG activities occurred simultaneously at right and left CM and surface at onset of all seizure types, with the exception of myoclonic seizures where CM complete discharges and individual spike-wave complexes significantly lead those of the surface. Brief tonic-atonic spasms clinically undistinguishable from "real" epileptic seizures showed no EEG counterparts at CM and surface. Interictal CM spike-wave complete discharges and individual spike-wave complexes showed variable amplitude-temporal patterns. Amplitude emphasis on CM and frontopolar regions was observed in most of complete discharges, however, and phase shifts between CM and frontopolar regions were observed in individual spike-wave complexes.
Adult↗
[Horseradish peroxidase labelled neurons of nonspecific thalamic nuclei projecting to the cat brain somatosensory zone I].
The morphology and topography of neurons whose axons form the thalamic nonspecific input to the primary somatosensory cortex were studied in the cat thalamus by the method of the retrograde transport of the horseradish peroxidase. The labelled cells were found in the dorsolateral part of the nucleus ventralis anterior, in the nucleus centralis lateralis, in the lateral part of the nucleus dorsalis medialis, in the dorsal part of the nucleus centrum medianum. A very small number of slightly stained cells were found in the nucleus paracentralis. The variety of the shape, size and intensity of labelling of the HRP-positive cells was observed in each thalamic structure. The results of the experiments indicate that not only the ventrobasal complex but also the nonspecific thalamic nuclei are projected to the primary somatosensory cortex. These data demonstrate the existence of multiple afferent thalamic inputs to the primary somatosensory cortex.
Afferent Pathways↗
Language disturbances from mesencephalo-thalamic infarcts. Identification of thalamic nuclei by CT-reconstructions.
The authors report the cases of two patients with CT-documented paramedian mesencephalo-thalamic infarcts, showing language disturbances. The first patient showed a non fluent, transcortical motor-like aphasia, the other had a fluent but severely paraphasic language disorder. The CT study disclosed that it was the dorso-median thalamic nucleus that was mostly involved in both cases. These findings agree with a few previous pathological studies suggesting that the paramedian thalamic nuclei, particularly the dorso-median nucleus may play some role in language disturbances. However the anatomical basis for thalamic aphasia remains speculative, taking into account the importance of cortical connections in the origin of subcortical neuropsychological disturbances.
Aged↗
[Responses of neurons of the medial group of thalamic nuclei to stimulation of the fronto-basal portions of the neocortex].
Neuronal and focal responses of medial thalamic nuclei (mediodorsal, central lateral, parecentral, centrum medianum, parafascicular) to stimulation of frontobasal cerebral cortex (proreal, posterior orbital, basal temporal regions) were studied in acute experiments on cats narcotized by nembutal mixed with chloralose. Proceeding from the data on the number of neurons responding to cortical stimulation and on the duration of the response latent period, three functionally heterogeneous sections of medial nuclei were distinguished: the microcellular and magnocellular regions of the mediodorsal nucleus, and the intralaminar nuclei with the parafascicular complex. Neurons were recorded which could be activated antidromically during stimulation of another region. On this basis a suggestion is made on the integrating function of medial nuclei providing unification of the frontobasal regions of the neocortex.
Animals↗
[Reactions of neurons of the parietal associative cortex field 7 to electric stimulation of the latero-dorsal and postero-lateral thalamic nuclei].
Neuronal responses of the parietal associative cortex (PAC) field 7 to the electrical stimulation of laterodorsal (LD) and posterolateral (PL) thalamic nuclei were studied in calypsol-narcotized cats. A correlation between depth, duration of the background activity inhibition and latent periods was determined for distribution of neurons responding to stimulation of associative nuclei by impulses. It is shown that there are functional relations between LD and field 7 of PAC. Common and specific peculiarities of neuronal responses of the associative cortex were found when a volley of impulses came from LD- and PA-nuclei of the thalamus.
Action Potentials↗