Mediodorsal Nucleus


To understand functional roles of the thalamic mediodorsal nucleus (MD) in sensory-to-motor information transformation during spatial working memory performance and compare with those of the dorsolateral prefrontal cortex (DLPFC), we calculated population vectors using a population of MD activities recorded during 2 tasks.  

The mediodorsal nucleus (MD) of the thalamus has reciprocal projections with the frontal cortex and limbic system, and may be involved in absence seizures.  

Controls showed greater activation during attended than ignored PPI conditions in all FST regions-dorsolateral prefrontal cortex (Brodmann areas 46, 9), striatum (caudate, putamen), and the thalamic mediodorsal nucleus.  

Ultrastructural analysis in the macaque mediodorsal nucleus revealed that thalamic interneurons are a main postsynaptic target of DAT-ir axons; this suggests that the marked expansion of the dopamine innervation in the primate in comparison to the rodent thalamus may be related to the presence of a sizable interneuron population in primates.  

Automatic relevance determination was performed on neural networks trained on this data, identifying NAA group differences in the pulvinar and mediodorsal nucleus, underscoring the importance of examining thalamic subregions in schizophrenia..  

This postmortem study examined mRNA expression of ionotropic glutamate receptor (iGluR) subunits and PSD95 in 5 precisely defined and dissected thalamic subdivisions (medial and lateral sectors of the mediodorsal nucleus; and the ventral lateral posterior, ventral posterior, and centromedian nuclei) of persons with schizophrenia and matched controls using quantitative PCR with normalization to multiple endogenous controls.  

Unlike other thalamic nuclei, the mediodorsal nucleus, which is the principal thalamic nucleus for the prefrontal cortex, has similarly widespread connections with the reticular nucleus.  

The anterior multiformis part of the mediodorsal nucleus but not middle and caudal levels had high DBH activity.  

Patients with schizophrenia demonstrated decreased anisotropy and increased longitudinal and transversal diffusivity within the pathways from the mediodorsal nucleus and the pulvinar to the orbitofrontal and parietal-occipital-temporal lobes.  

The prefrontal cortex, excited by the visual stimulus via the mediodorsal nucleus of the thalamus, mediates the descending influence on the activity of dopaminergic cells, simultaneously controlling dopamine release in different areas of the striatum and thus facilitating the mutual selection of neural reflections of the individual properties of the visual stimulus and their binding into an integral image..  

CONCLUSION: Acute thalamic chronotaraxis is a specific clinical picture that accurately predicts a small artery disease of the thalamus involving the mediodorsal nucleus of the thalamus.  

Patients also showed significantly lower relative glucose metabolism in the frontal and temporal lobes, caudate nucleus, cingulate gyrus, and mediodorsal nucleus of the thalamus relative to normal volunteers, which is consistent with earlier studies.  

For area PEa, the corticothalamic projection formed by small endings was found mainly in LP, VPL, anterior pulvinar (PuA), lateral pulvinar (PuL), PuM and, to a lesser extent, in ventral posterior inferior nucleus (VPI), CL, mediodorsal nucleus (MD) and CM.  

The dysgranular and agranular regions lying on the orbital and medial surfaces of the frontal lobes were most closely connected with limbic structures including cingulate cortex, amygdala, parahippocampal cortex, subiculum, hippocampus, hypothalamus, medial caudate nucleus, and nucleus accumbens as well as the magnocellular division of the mediodorsal nucleus of the thalamus and midline thalamic nuclei, consistent with findings in the rhesus monkey.  

Several studies have pointed to alterations in mean volumes, neuron densities and total neuron numbers in the caudate nucleus (CN), putamen, nucleus accumbens (NA), mediodorsal nucleus of the thalamus (MDNT) and lateral nucleus of the amygdala (LNA) in schizophrenia.  

The aim of this study was to quantify the total number of neurons and glial cells in the mediodorsal nucleus of the thalamus (MD) of 8 newborn human brains, in comparison to 8 adult human brains.  

A network of subcortical structures, including the mediodorsal nucleus of the thalamus and striatum were the only regions showing activity that was exclusively correlated with the neurocognitive demands of reversing SR associations.  

D2 receptor availability was significantly lower in the orbitofrontal cortex, primary motor cortex, anterior cingulate gyrus, mediodorsal nucleus of thalamus, and hippocampus, areas important for motivation and reward, sensory gating, movement, and attention.  

In the thalamus, neurons in the mediodorsal nucleus relay a corollary discharge of saccades from the midbrain superior colliculus to the cortical frontal eye field.  

Intercorrelations of the mediodorsal nucleus were widespread with the prefrontal cortex (9 out of 10 Brodmann's areas in the left hemisphere) and temporal lobe (10 out of 11 Brodmann's areas in the left hemisphere) while the pulvinar correlated only with the parietal and occipital cortical areas.  

NP was also accompanied by activation of the right thalamus, particularly the mediodorsal nucleus, which has been implicated in the pathophysiology of schizophrenia, a condition associated with diminished NP effects.  

Conversely, using the identical statistical paradigm, bilateral anterior insular cortices, the right anterior cingulate, orbitofrontal cortex, amygdala, midbrain and mediodorsal nucleus of the thalamus showed decreased neural activation.  

RESULTS: A metabolic disconnection was observed in patients with schizophrenia in the left hemisphere between the mediodorsal nucleus and widespread frontotemporal cortical regions, and stronger-than-normal intercorrelations were found between the pulvinar and superior temporal, selected parietal, posterior cingulate, and occipital areas. CONCLUSIONS: Deficits in the functional interrelationships between the left frontotemporal cortices and the left mediodorsal nucleus of the thalamus complement inferences from postmortem and magnetic resonance imaging volumetric studies identifying a thalamic diathesis in schizophrenia..  

The mediodorsal nucleus of the thalamus (MD) represents the main subcortical structure that projects to the prefrontal cortex (PFC) and it regulates key aspects of the cognitive functions of this region.  

Val/Val) and the mediodorsal nucleus of the thalamus (Met/Met vs.  

The main thalamic afferentation of the prefrontal cortex (PFC) originates in the mediodorsal nucleus (MD).  

The effects of ibotenic acid lesions of the mediodorsal nucleus of the thalamus (MD) on memory and fear reactivity in mice were studied.  

Distinct thalamic nuclei were morphologically analyzed with qualitative methods with an emphasis on the mediodorsal nucleus.  

To clarify the brain regions where selective serotonin reuptake inhibitors act, we examined the effect of microinjection of the selective serotonin reuptake inhibitor, citalopram, into the amygdala, medial prefrontal cortex and mediodorsal nucleus of the thalamus on freezing behavior, an index of fear, induced by conditioned fear stress. Bilateral injection of citalopram into the amygdala before testing reduced freezing significantly, while bilateral injection into the medial prefrontal cortex or mediodorsal nucleus of the thalamus did not.  

Although the reciprocal interconnections between the prefrontal cortex and the mediodorsal nucleus of the thalamus (MD) are well known, the involvement of inhibitory cortical interneurons in the neural circuit has not been fully defined.  

Furthermore, microinjections of muscimol (100 and 200 pmol/side) in the mediodorsal nucleus of the thalamus in GAERS rats suppressed seizures. These results suggest that the mediodorsal nucleus of the thalamus could be involved in absence seizures modulation.  

Much evidence from animal and clinical studies has shown that the mediodorsal nucleus of the thalamus (MD) is related to various types of memory, such as visual recognition, object-reward association, spatial working, and reference memory; however, few studies have investigated its role in emotion-related learning and memory processes. Both pre- and posttraining lesions of the mediodorsal nucleus of the thalamus significantly attenuated conditioned freezing but had no effect on postshock freezing. Our results suggest that the mediodorsal nucleus of the thalamus has an important role in acquisition, consolidation or retrieval in Pavlovian contextual fear conditioning.  

The thalamic mediodorsal nucleus (MD) has strong reciprocal connections with the dorsolateral prefrontal cortex (DLPFC), suggesting that the MD, like the DLPFC, participates in higher cognitive functions.  

Since birth, a dense retrograde labeling has been found in the mediodorsal nucleus, which increased progressively from P4 to P8 and began to decrease at P10 until P13 (67.37% vs.  

RESULTS: Over the left prefrontal cortex, 1-Hz TMS was associated with increased activity at the site of stimulation as well as in connected limbic regions: bilateral middle prefrontal cortex, right orbital frontal cortex, left hippocampus, mediodorsal nucleus of the thalamus, bilateral putamen, pulvinar, and insula (t = 3.85, p <.001).  

Subsequent histological analyses of brain tissue were conducted to determine quantitatively the neuronal losses in both the mediodorsal nucleus of the thalamus (MDN) and the nucleus basalis magnocellularis (NBM).  

However, inhibition of the basolateral amygdala, mediodorsal nucleus of the thalamus, or the ventral prefrontal cortex had no effect on drug-seeking behavior.  

OBJECTIVE: Three thalamic nuclei--the mediodorsal nucleus, pulvinar, and centromedian nucleus--each have unique reciprocal circuitry with cortical and subcortical areas known to be affected in schizophrenia. To determine if the disorder is also associated with dysfunction in the mediodorsal nucleus, pulvinar, and centromedian nucleus, relative glucose metabolism in these regions was measured in a large group of unmedicated patients with schizophrenia. The PET and MRI images for each subject were coregistered, and the whole thalamus, mediodorsal nucleus, pulvinar, and centromedian nucleus were traced on the MRI image. RESULTS: Patients with schizophrenia showed significantly lower relative glucose metabolism in the mediodorsal nucleus and the centromedian nucleus and significantly higher relative glucose metabolism in the pulvinar, compared with the healthy subjects. Lower relative glucose metabolism in the total thalamus, mediodorsal nucleus, and pulvinar was associated with greater overall clinical symptoms as measured by the Brief Psychiatric Rating Scale. Lower relative glucose metabolism in the pulvinar was associated with more hallucinations and more positive symptoms, while lower relative glucose metabolism in the mediodorsal nucleus was associated with more negative symptoms.  

Results have revealed that (1) the forelimb is represented predominantly in the PMdr, while only a few sites representing other body parts are distributed as embedded within the forelimb representation; (2) the corticostriatal input zone is located in the striatal cell bridges and their surroundings; (3) the cells of origin of the thalamocortical projections to the PMdr are located mainly in the parvicellular division of the ventroanterior nucleus, the oral divison of the ventrolateral nucleus, area X, the caudal divison of the ventrolateral nucleus, the mediodorsal nucleus, and the intralaminar nuclear group; (4) the PMdr is interconnected primarily with higher-order motor-related areas and dorsal area 46.  

Breathing period and expiratory time were also increased when the stimulations involved the intralaminar wing surrounding the mediodorsal nucleus, the rostral central gray, zona incerta, and ventral tegmental area.  

Firstly, the anterior and mediodorsal nucleus are involved in processing the contents of the stimuli for storage and recall. The anterior nuclei influence the selection of material to be stored and remembered, whereas the mediodorsal nucleus is involved in the coordination and selection of the strategies used to retrieve material.  

In contrast, projections to d-area 23b originate from the nucleus lateralis posterior, medial pulvinar, nucleus centralis latocellularis, mediodorsal nucleus and nucleus ventralis anterior and lateralis and weakly from the anterior nuclei.  

DESIGN: Postmortem sections containing the thalamic mediodorsal nucleus were subjected to in situ hybridization with mouse Dlx1 and human SHOX2 RNA probes.  

The medial prefrontal cortex (mPFC), defined as the cortical region that has a reciprocal innervation with the mediodorsal nucleus of the thalamus, is also a terminal region of the mesocorticolimbic dopamine system.  

Combining our results with anatomical and electrophysiological facts, it is suggested that the thalamofrontal circuit involving the rostral reticular and the mediodorsal nucleus of the thalamus is responsible for the generation of 12 Hz frontal spindles in humans..  

Four studies have reported that the mediodorsal nucleus of the thalamus (MD) is smaller and contains fewer neurons in schizophrenia.  

The major association thalamic nuclei, the mediodorsal nucleus (MD) and the medial pulvinar nucleus (PUM) are regarded as important parts of the circuits among association cortical regions.  

Co-registration of the magnetic resonance image to a stereotactic atlas of the human thalamus revealed that the lesion was confined to a small subgroup of paramedian nuclei, including the parvocellular part of the mediodorsal nucleus. Voluntary eye closure may involve direct cortico-nuclear connections and indirect pathways through the paramedian thalamus, most probably through the mediodorsal nucleus..  

The mediodorsal nucleus (MD) is the thalamic gateway to the prefrontal cortex, an area of the brain associated with spatial and object working memory functions.  

Somewhat less intense activation in the central nucleus of the amygdala (AMc), and transient activation in the piriform cortex and the mediodorsal nucleus of the thalamus were observed.  

In addition, metabolic activity was increased in the dorsolateral and dorsomedial prefrontal cortex, as well as in the mediodorsal nucleus of the thalamus.  

PURPOSE: Status epilepticus (SE) was previously found to induce damage in the mediodorsal nucleus of the thalamus (MD) in both adult and immature rats.  

Anteroventral nucleus had decreased ACh content after PPTg lesion, but a time dependent increase was found in mediodorsal nucleus; ACh concentration was unchanged in thalamic reticular nucleus or medial geniculate.  

Rabbits received lesions of the mediodorsal nucleus of the thalamus (MDN) or sham lesions and were subjected to classical eyeblink (EB) and heart rate (HR) conditioning.  

Abnormalities in thalamic nuclei parallel these findings-the pulvinar, which projects to temporal association and sensory cortices, is reduced in both disorders, but the mediodorsal nucleus, which projects extensively to the frontal cortex, is reduced in schizophrenic patients but not in schizotypal patients.  

OBJECTIVE: The authors assessed schizophrenia-associated changes in volume and neuronal number in the mediodorsal nucleus and the pulvinar regions of the thalamus. Computer-assisted morphometric techniques were used to determine volumes for the mediodorsal nucleus, pulvinar, and the anterior and centromedian nuclei as well as the parvocellular, magnocellular, and caudodorsal subdivisions of the mediodorsal nucleus. Neurons in the mediodorsal nucleus and pulvinar were counted and measured by using a stereology-based sampling strategy. In analyses that included either the full cohort or only the subjects without Alzheimer's type pathology, volumes of the mediodorsal nucleus and pulvinar, but not the anterior or centromedian nuclei, were significantly smaller in the schizophrenic subjects. For the schizophrenic subjects, neuronal number in the mediodorsal nucleus, parvocellular subdivision, and pulvinar was significantly lower, and neuronal size in the mediodorsal nucleus, caudodorsal subdivision, and pulvinar was significantly smaller. CONCLUSIONS: Schizophrenia is associated with volume and neuronal changes in the mediodorsal nucleus and pulvinar, the major association nuclei of the thalamus, whereas total thalamic volume and the volumes of anterior and centromedian nuclei were not significantly altered..  

Our further demonstration of strong mPFC projections to several additional thalamic nuclei, particularly to the mediodorsal nucleus, suggests that these thalamic nuclei, like RE, represent important output stations (or gateways) for the actions of mPFC on diverse subcortical and cortical structures of the brain..  

Computed tomography and magnetic resonance imaging revealed cerebral haemorrhage in the right thalamus involving the ventral anterior nucleus, medioventral nucleus, mamillothalamic tract, internal medullary lamina, and mediodorsal nucleus.  

The effects of excitotoxic lesions of the mediodorsal nucleus of the thalamus, the anterior thalamic nuclei and of the prelimbic cortex were examined on two tests of discrimination and reversal learning. However, when stimulus-reward contingencies were reversed, animals with lesions of the mediodorsal nucleus of the thalamus made significantly more errors than control animals or animals of other lesion groups. However, lesions of the mediodorsal nucleus of the thalamus resulted in a mild impairment according to number of sessions required to attain criterion performance of the task when the response rule was reversed. The results of the present study provide evidence for a role for the mediodorsal nucleus of the thalamus in new learning, particularly when stimulus-reward contingencies are reversed.  

We examined the stimulating effect of Substantia Innominata pars anterior (SIa), during the waking state, on the 'central' part of the mediodorsal nucleus of the thalamus (MD), combining electrophysiological and anatomical techniques in restrained, undrugged, unanaesthetized cats.  

Surprisingly, area 3a receives the majority of its input from thalamic nuclei associated with the motor system, posterior division of the ventral lateral nucleus of the thalamus (VL), the mediodorsal nucleus (MD), and intralaminar nuclei including the central lateral nucleus (CL) and the centre median nucleus (CM).  

Analysis of the sections indicated consistent neuronal damage in the central and lateral segments of the mediodorsal nucleus of the thalamus, which was confirmed using adjacent cresyl violet-stained preparations.  

The behavioral effects of lesions of the prelimbic cortex (PL), mediodorsal nucleus of the thalamus (MD), and anterior thalamic nuclei (ANT) were investigated in 2 attentional tasks in rats: the 5-choice serial reaction time task and a vigilance task.  

(3) The mediodorsal nucleus of the thalamus and the caudate nucleus responded with an increase in signal which returned to baseline after approximately 15 to 30 s.  

After a single iontophoretic injection of PHA-L into a FEF site where intracortical microstimulation elicited eye movements, anterogradely labelled fibres and terminal-like elements were found in the thalamus in the anterior nuclei, intralaminar nuclei, lateral portion of the mediodorsal nucleus and posterior nuclear group.  

In thalamus, all three drugs increased GAD expression in the reticular nucleus, whereas only haloperidol decreased GABA(A) binding in the mediodorsal nucleus, actions consistent with a reduction in nigrothalamic, GABA-mediated neural transmission. Haloperidol, in contrast, has a broad and potent action in basal ganglia, causing changes in SNR and in the mediodorsal nucleus, while also altering GAD mRNA in RtN, potentially reflective of its dyskinetic and antipsychotic actions..  

Because frontal and temporal lobe volumes are diminished in schizophrenia, volume loss could characterize their primary thalamic relay nuclei (mediodorsal nucleus [ MDN] and pulvinar).  

The involvement of efferent projections was determined by microinjecting the local anesthetic procaine into the mediodorsal nucleus of the thalamus (MD) or the midbrain extrapyramidal area (MEA) prior to administering DAMGO or AMPA into the ventral pallidum.  

The lesions were located within the pulvinar, the sensory nuclei, the mediodorsal nucleus, and the ventral lateral posterior nucleus (according to the classification of Hirai and Jones), the latter including the ventral intermediate nucleus (Vim according to the classification of Hassler).  

Moderate densities of parvalbumin staining are also present in regions of the mediodorsal nucleus (MD).  

The effects of the associated mediodorsal nucleus of the thalamus on spike activity of respiratory neurons in the medulla oblongata and on respiration were studied in normal conditions and in oxygen insufficiency. At normal atmospheric pressure, before animals were elevated to low pressures, electrical stimulation of the mediodorsal nucleus of the thalamus had predominantly inhibitory effects. In these conditions, the inhibitory effect of stimulation of the mediodorsal nucleus of the thalamus was less marked than in normoxic conditions.  

In the thalamus, the main difference compared to the adult pattern was observed in the mediodorsal nucleus which, in early development, showed a high immunosignal, however, by postnatal day 22 the immunoreactivity decreased with only some scattered cells labelled in the adult brain..  

Cortical input to areas 46 and 8 is complemented by projections from the thalamic multiform and parvicellular sectors of the mediodorsal nucleus associated with oculomotor functions and working memory.  

Using stereological techniques in six pairs of individually matched brains from schizophrenics and controls, we measured the volumes and obtained estimates of the number of neurons in the three subnuclei (parvocellular, pc; densocellular, dc; magnocellular, mc) of the mediodorsal nucleus (MD) and from the ventral posterior medial nucleus.  

Results indicated that AA rats had a significantly greater content of proopiomelanocortin mRNA in the arcuate nucleus of the hypothalamus, of proenkephalin mRNA in the prefrontal cortex and of prodynorphin mRNA in the mediodorsal nucleus of the thalamus (p < or = .05).  

Neurodegeneration and neural injury in the caudate nucleus and mediodorsal nucleus of the thalamus were investigated in a postmortem study of 11 prospectively accrued, clinically well-characterized elderly people with schizophrenia, 11 elderly control subjects with no neuropsychiatric illness, and 12 subjects with Alzheimer's disease.  

IL has prominent projections to the central nucleus of the amygdala (Ce), the mediodorsal nucleus of the thalamus (MD), the lateral hypothalamic area (LHA), the periaqueductal gray (PAG), the parabrachial nucleus (Pb), and the nucleus of the solitary tract (NTS).  

Emerging data also confirms neuropathology in the mediodorsal nucleus of the thalamus that projects to the DLPFC.  

A sporadic type was mainly found in the parvocellular division of the mediodorsal nucleus (96.8% of the cells recorded) and in the centre median-parafascicular complex (74.2%). Two other types of activities characterized by random or rhythmic bursts fulfilling the extracellular criteria of low-threshold calcium spike bursts were concentrated in the central lateral nucleus (62.3%) and the paralamellar division of the mediodorsal nucleus (34.1%).  

The results indicate that damage to the mediodorsal nucleus of the thalamus, the midline nuclei or the intralaminar nuclei, or a combined lesion of these structures may be responsible for deficits of executive functioning..  

Layer IV, the target for axons from the mediodorsal nucleus of the thalamus, conveys information from other associational cortices, cerebellum, basal ganglia, and the reticular and limbic systems.  

Rostral AGm is interconnected with the lateral portion of the mediodorsal nucleus (MD1), VL, and the central lateral (CL), paracentral (PC), central medial, rhomboid and ventromedial nuclei.  

Seven days post-lesion, a 20-30% decrease in Bmax values (P < 0.05) was found in the nuclei receiving input from the lesioned nucleus reticularis thalami sector (the mediodorsal nucleus and densicellular and magnocellular parts of the ventral anterior nucleus) without changes in affinity.  

RESULTS: Significance probability mapping (with resampling) identified an area in the region of the mediodorsal nucleus bilaterally with significantly lower relative metabolism in the schizophrenia group than in either the control or schizotypal personality disorder groups, which did not differ from each other. Shape analyses revealed that schizophrenic patients had significantly fewer pixels in the left anterior region, whereas patients with schizotypal personality disorder had significantly fewer pixels in the region of the right mediodorsal nucleus than did control subjects.  

Thalamic labeling after cFr2 injections was present in anteromedial nucleus (AM), ventrolateral nucleus (VL), lateral segment, mediodorsal nucleus (MDl), centrolateral nucleus (CL), ventromedial nucleus (VM), posterior nucleus (Po) and lateral posterior nucleus (LP). Area Fr1 receives thalamic input from nuclei VL, anteroventral nucleus (AV), CL and Po, but none from mediodorsal nucleus (MD) or LP, and its input from VM is reduced.  

[ 6] finding a significant (P < 0.05) nerve cell loss in the thalamic mediodorsal nucleus in Huntington's disease with the so-called V(Ref) x N(V) method.  

We estimated the total neurone number, glial number, and glial index (ratio glial cells/neurone) in the thalamic mediodorsal nucleus (MD) in seven patients suffering from Huntington's disease (HD; four males, three females, mean age 52.4 +/- 13.6 years) and age- and sex-matched controls (four males, three females, mean age 53.6 +/- 12.1 years) by means of a stereological protocol.  

Thalamic inputs to the motor cortical areas (M1, SMA, PMd, and PMv), in general, were segregated from those directed to area 46, except in the mediodorsal nucleus, in which there was clear overlap of the territories sending projections to area 46, SMA-proper, and PMdc..  

Among the nuclei with metabolic changes, the hippocampus and the mediodorsal nucleus of the thalamus may be related to the therapeutic action of risperidone and require further study..  

In the medial thalamus, degeneration was frequently seen within the intralaminar nuclei, and somewhat less frequently observed within the paraventricular nucleus, the mediodorsal nucleus, and the gelatinosis nucleus.  

The main findings of this study are as follows: (1) few double-labeled cells were found after two injections in different sectors of the caudate nucleus; (2) double-labeled neurons were more abundant after adjacent injections and they were mainly located in the caudal intralaminar nuclei, in the rhomboid nucleus and in the dorsal mediodorsal nucleus; and (3) there were variations in the spatial organization of the thalamostriatal neurons projecting to various sectors of the caudate nucleus in the different thalamic nuclei known to project to this part of the striatum..  

These findings suggest that the midline thalamic nuclei, like the mediodorsal nucleus of the thalamus, process information required for response selection under non-optimal learning conditions..  

Anatomical analysis revealed that progesterone treatment decreased the amount of neuronal death seen in the striatum and the mediodorsal nucleus of the thalamus.  

The present experiments investigated the effects of excitotoxic, axon-sparing lesions of the mediodorsal nucleus of the thalamus (MD) on locomotor activity and i.v.  

The present study has investigated, using unbiased quantitative methods with randomized systematic sampling, the total neuronal cell numbers in the mediodorsal nucleus of the thalamus after aspiration lesions of the medial prefrontal cortex performed in neonatal and in adult rats. On the other hand, the volume of the mediodorsal nucleus was reduced by 27% in neonatally, and 20% in adult lesioned animals. Total neuronal cell number of the mediodorsal nucleus was significantly decreased in neonatally as well as in adult lesioned rats, by 14% and 21%, respectively.  

Agranular posterior insular cortex projected to medial mediodorsal nucleus, agranular anterior insular and infralimbic cortices as well as granular and dysgranular posterior insula.  

The mediodorsal nucleus of the thalamus (MD) has connections with central autonomic centers involved in cardiovascular control and undergoes severe degeneration in fatal familial insomnia, a human disease characterized by progressive dysautonomia.  

In contrast, the giant endings originating from SMA and PMd were located in a thalamic nucleus (mediodorsal nucleus) distinct from the main termination zone formed by small endings.  

The present study examined projections of GABAergic and cholinergic neurons from the basal forebrain and preoptic-anterior hypothalamus to the "intermediate" part of the mediodorsal nucleus of the thalamus. Retrograde transport from this region of the mediodorsal nucleus was investigated using horseradish peroxidase-conjugated wheatgerm agglutinin in combination with peroxidase-antiperoxidase immunohistochemical staining for glutamic acid decarboxylase and choline acetyltransferase. The choline acetyltransferase-positive mediodorsal-projecting neurons are morphologically different from the choline acetyltransferase-positive neurons in the basal forebrain, suggesting that those projecting to the mediodorsal nucleus are a small proportion of the cholinergic neuronal population in the basal forebrain. The highest percentage of mediodorsal-projecting GABAergic neurons is in the anterior lateral hypothalamus where more than 25% of the total population of glutamic acid decarboxylase-positive cells project to the mediodorsal nucleus of the thalamus. Overall, of the large population of retrogradely-labelled neurons in the basal forebrain and preoptic-anterior hypothalamus, a significant proportion are glutamic acid decarboxylase-positive neurons (> 60% in the basal forebrain and > 30% in the preoptic-anterior hypothalamus), while the choline acetyltransferase-positive neurons amount to a smaller percentage of the neurons projecting to the mediodorsal nucleus (< 13% in the basal forebrain and < 2% in the preoptic-anterior hypothalamus). These results provide anatomical evidence of direct GABAergic projections from the basal forebrain and preoptic-anterior hypothalamic regions to the "intermediate" part of the mediodorsal nucleus in the cat. This GABAergic projection field could be the direct pathway by which the basal forebrain directly modulates thalamic excitability and may also be involved in mechanisms modulating electroencephalographic synchronization and sleep through the "intermediate" mediodorsal nucleus..  

The origin of the corticothalamic projections to the contralateral mediodorsal nucleus, the collateralization of cortical fibers and their synaptic organization in the ipsi- and contralateral mediodorsal nuclei were investigated in adult rats with double retrograde fluorescent and anterograde tracing. At the electron microscopic level, unilateral injections of biotinylated dextran-amine in the orbitofrontal cortex resulted in anterograde labeling of small terminals and a few large boutons in the ipsilateral mediodorsal nucleus, while only small boutons were identified contralaterally. The diameter of postsynaptic dendritic profiles contacted by labeled small cortical endings was significantly larger in the ipsilateral mediodorsal nucleus than contralaterally. These findings demonstrate that dense contralateral cortical projections to the mediodorsal nucleus derive from the orbital and agranular insular areas, and that crossed corticothalamic afferents are mostly formed by collaterals of the ipsilateral connections. Our observations also point out the heterogeneity of corticothalamic boutons in the rat mediodorsal nucleus and morphological differences in the synaptic organization of prefrontal fibers innervating the two sides, indicating that ipsilateral cortical afferents may be more proximally distributed than crossed cortical fibers on dendrites of mediodorsal neurons..  

The mediodorsal nucleus was unique among thalamic nuclei because it contained a wide variety of intensely immunostained perikarya embedded in a moderately-labelled neuropil.  

Three rhesus monkeys with unilateral amygdala removals received bilaterally symmetrical injections of a retrograde fluorescent tracer into the medial portion of the mediodorsal nucleus of the thalamus.  

As visualized on X-ray film autoradiographs, high levels of CR gene transcript occurred in several thalamic nuclei, including the reticular nucleus, mediodorsal nucleus, rostral intralaminar nuclei (paracentral, central medial and central lateral) and several midline nuclei (paraventricular, reuniens and medioventral nuclei). In contrast, virtually all neurons in the rostral intralaminar and midline nuclei expressed very high levels of CR mRNA and formed a prominent rim around the mediodorsal nucleus, which contained scattered clusters of labeled neurons.  

Significant decreases in cytochrome oxidase activity were found in motor areas and limbic structures, such as hippocampus, piriform cortex, fundus striatum, globus pallidus, substantia nigra pars reticulata, mediodorsal nucleus of the thalamus, ventral pallidum, and interpositus nucleus of the cerebellum.  

Rabbits received lesions of the mediodorsal nucleus of the thalamus (MD) or sham lesions and were subjected to classical eyeblink (EB) and heart rate (HR) conditioning.  

We believe that this last system, which includes the mediodorsal nucleus, nucleus ventralis anterior, and cingulate cortex, plays a significant role in central command..  

The neurons that project to the FEFsem are distributed in (1) the rostral portion of the ventral lateral nucleus, pars caudalis, (2) the caudal portion of the ventral lateral nucleus, pars caudalis, (3) the mediodorsal nucleus, (4) the ventral anterior nucleus, pars parvocellularis, and (5) the ventral anterior nucleus, pars magnocellularis. In contrast, the large majority of neurons that project to the FEFsac are located in the paralaminar region of the mediodorsal nucleus.  

When compared with other cortical laminae, layer IV receives most of its synaptic input from the mediodorsal nucleus of the thalamus.  

The ventral pallidum, through its projections to the mediodorsal nucleus of the thalamus, has been considered as the main output structure of the prefrontal-basal ganglia circuits. When the biocytin injections were made into this ventral pallidal region, anterogradely labelled fibres were observed in both the dorsomedial substantia nigra pars reticulata and the medial subthalamic nucleus, but not in the mediodorsal nucleus of the thalamus. Among these responding cells, 43% were antidromically driven from the subthalamic nucleus, 30% from the substantia nigra pars reticulata and only 6% from the mediodorsal nucleus of the thalamus.  

These nuclei include the ventrobasal complex, the nucleus reticularis thalami, the mediodorsal nucleus, and the dorsal thalamic system with special reference to the habenula..  

The thalamus showed a distinctive heterogeneous distribution of cannabinoid receptors, with the highest concentration of receptors localized in the mediodorsal nucleus, anterior nuclear complex, and in the midline and intralaminar complex of nuclei, i.e.  

Electrical stimulation of the adjacent medial thalamic nuclei (mediodorsal nucleus (MD) or centromedial nucleus (CM)) and ventrobasal complex (VB) of the thalamus had very little effect on the VSR.  

These characteristics indicate that: (1) SHL and medial and dorsal parts of DMA and DMP are comparable to mammalian midline thalamic nuclei, including the medial components of the intralaminar nuclei; (2) lateral parts of DMA and DMP are comparable to the mediodorsal nucleus in mammals; (3) DIP is comparable to the parafascicular nucleus in mammals; and (4) DLM and DLP are comparable to the laterally located intralaminar nuclei in mammals.  

Lesions of the lateral-internal medullary lamina site in thalamus and the medial wall area in frontal cortex produced impairments that were significantly greater than for lesions of the mediodorsal nucleus in thalamus, the fornix, or the dorsal hippocampus.  

Each orbital area is connected with a particular segment of the mediodorsal nucleus. The medial orbital area receives its principal thalamic afferents from the parataenial nucleus, the dorsocentral portion of the mediodorsal nucleus, and the ventromedial portion of the submedial nucleus. The ventral orbital area receives input from the lateral segment of the mediodorsal nucleus, the rostromedial portion of the submedial nucleus, and the central lateral nucleus. Thalamic afferents to the ventrolateral orbital area arise from the entirety of the submedial nucleus and from the lateral segment of the mediodorsal nucleus. The lateral orbital area receives thalamic afferents from the central segment of the mediodorsal nucleus, the ventral portion of the submedial nucleus, and the ventromedial nucleus.  

Retrogradely labeled neurons were distributed primarily in the parvicellular division of the ventroanterior nucleus (VApc), oral division of the ventrolateral nucleus (VLo), area X, and mediodorsal nucleus (MD).  

An MRI study revealed bilateral lesions limited to the thalamus involving most of the right anterior nucleus (AN), mediodorsal nucleus (MD), ventrolateral nucleus (VL), and centromedial nucleus (CM), as well as a small part of the left MD, and CM.  

The mediodorsal nucleus displayed a markedly heterogeneous staining, with numerous clusters of labeled cells and fibers in its central parvicellular part.  

However, the great majority of amygdaloid neurons with projections to the mediodorsal nucleus did not exhibit glutamate or aspartate immunoreactivity.  

Thalamic lesions were aimed at the lateral internal medullary lamina (L-IML) and cortical lesions at the projection areas of the mediodorsal nucleus along the medial wall (MW) and dorsal to the rhinal sulcus (RS) in frontal cortex.  

Retrograde and anterograde tract-tracing studies were carried out to determine whether the capacity of the nucleus accumbens to influence the thalamic mediodorsal nucleus via ventral striatopallidothalamic connections disproportionately favors the shell over the core subterritory. mediodorsal nucleus-projecting rostroventral forebrain neurons were most numerous in the ventromedial part of the subcommissural ventral pallidum and pallidal parts of the olfactory tubercle. Injection into the ventromedial part of the subcommissural ventral pallidum resulted in robust anterograde labeling of the medial segment of the mediodorsal nucleus and ventral tegmental area and weak labeling of the substantia nigra and subthalamic nucleus. Conversely, after injection into the dorsolateral part of the subcommissural ventral pallidum, anterograde labeling was weak in the mediodorsal nucleus and ventral tegmental area, but robust in the substantia nigra and subthalamic nucleus. The results are consistent with a predominant accumbens shell influence on the mediodorsal nucleus and with cortico-ventral striatopallidal-thalamocortical pathways that begin and end in different parts of the frontal lobe..  

In normoxia, the orbitofrontal cortex and thalamic mediodorsal nucleus (MDN) basically inhibit the pulse activity of bulbar respiratory neurons and respiration in general.  

The aim of this study was to determine whether forebrain neurons projecting to the mediodorsal nucleus of the thalamus in rats express glutamate decarboxylase messenger RNA as a marker for GABAergic neurons. Forebrain glutamate decarboxylase messenger RNA-containing neurons that project to the mediodorsal nucleus were identified using a combination of retrograde tracing with Fluoro-Gold and in situ hybridization for the messenger RNA encoding the 67,000 molecular weight synthetic enzyme for GABA. Glutamate decarboxylase messenger RNA-containing afferents to the mediodorsal nucleus were observed in the olfactory tubercle, vertical limb of the diagonal band of Broca, ventral pallidum, sublenticular substantia innominata, globus pallidus, lateral preoptic area, bed nucleus of the stria terminalis and reticular nucleus of the thalamus. The largest proportions of glutamate decarboxylase messenger RNA-containing afferents to the mediodorsal nucleus were observed in the vertical limb of the diagonal band, ventral pallidal parts of the olfactory tubercle and the reticular nucleus of the thalamus. These data suggest that a GABAergic projection from the basal forebrain to the mediodorsal nucleus of the thalamus can influence the function of this nucleus..  

The aim of this study was to determine how GABA receptors in the mediodorsal nucleus of the thalamus in rats might contribute to the regulation of locomotor behavior. Microinjections of the GABAB and GABAA agonists, baclofen and muscimol, into the mediodorsal nucleus produced dose-dependent increases in locomotion that were blocked by co-administration of the GABAB antagonist, 2-hydroxysaclofen. Microinjection of baclofen along the midline, lateral into the ventrolateral thalamus or into the lateral ventricles produced significantly smaller dose-dependent increases in locomotion, indicating that the anatomical locus for baclofen-induced locomotion resides in the mediodorsal nucleus. These results suggest that GABAergic afferents to the mediodorsal nucleus may oppose a tonic inhibitory tone on locomotor activity.  

The counts were relatively high in occipital visual association cortex and area TE of temporal cortex, intermediate in perirhinal cortex, entorhinal cortex, anterior cingulate cortex and the diagonal band of Broca, and low in the hippocampal formation and mediodorsal nucleus of the thalamus.  

Lesion experiments ruled out the possibility that impulse traffic via the thalamic mediodorsal nucleus (MD) contributed to the responses.  

Unilateral electrical stimulation of the centrolateral nucleus induced: (i) local increase in metabolic activity within the stimulated centrolateral nucleus and the ipsilateral thalamic mediodorsal nucleus, (ii) metabolic depression in all layers of the ipsilateral frontal cortex, (iii) bilateral increase in glucose consumption within the periaqueductal gray, pedunculopontine nucleus, and pontine reticular formation, and (iv) contralateral metabolic activation in the deep cerebellar nuclei.  

The thalamic neurons were activated through disinhibition by perfusion of the GABAA antagonist bicuculline-methyl chloride via a microdialysis cannula placed in the mediodorsal nucleus of the thalamus.  

Moreover, AChE activity reveals previously unrecognized heterogeneities within several thalamic nuclei, like the ventral anterior (VA), where a new ventromedial subdivision (VAvm) is described, the medial pulvinar (PulM) or the mediodorsal nucleus (MD).  

In addition, the medial region of the ventral striatum receives numerous projections from the central superior lateral nucleus, the magnocellular subdivision of the ventral anterior nucleus, and parts of the mediodorsal nucleus. After injection into the lateral region of the ventral striatum, few labeled neurons are seen scattered in nuclei of the intralaminar and ventral thalamic groups and occasional labeled cells in the mediodorsal nucleus.  

None of the injections resulted in labelled cells in the gustatory thalamic nucleus ventralis posterior medialis, pars parvocellularis, although all injections resulted in label of the mediodorsal nucleus of the thalamus.  

Wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) and biotinylated dextran amine (BDA) were used as tracers to study nucleus reticularis (NRT) connections with the mediodorsal nucleus (MD).  

Bilateral infusions of NMDA into thalamic mediodorsal nucleus, the intralaminar central lateral/paracentral nucleus, ventroposterolateral, or reticular nucleus of the thalamus in conscious rats, prior to GHB administration suppressed GHB-induced SWD in a dose dependent manner.  

Chronic changes in the thalamic mediodorsal nucleus (MD) after unilateral lesions of the prefrontal cortex were studied with the aid of quantitative light, and electron microscopic immunohistochemistry.  

Rabbits received ibotenic acid lesions of the mediodorsal nucleus of the thalamus (MD) or sham lesions.  

The latency to onset of the ipsps in the mediodorsal nucleus and in the reticular nucleus were not substantially different (1.7 +/- 1.1 msec vs. These experiments support a dual functional role for limbic system output from the basal ganglia in the regulation of thalamocortical activity: a) a direct inhibitory projection from the VP to the mediodorsal nucleus and b) an indirect disinhibition of neurons in other dorsal thalamic nuclei that occurs via a direct inhibitory projection to the reticular nucleus of the thalamus.  

These subfields consist of the rostral pole of the mediodorsal nucleus with the exception of its central segment and a region of the ventral medial nucleus, medial to the mammillothalamic tract.  

Lesions of the mediodorsal nucleus (MDT), inflicted on the day of birth, caused no significant changes in prefrontal architecture on day 35.  

This study was undertaken to identify the neurotransmitter of the projection from the thalamic mediodorsal nucleus (MD) to the prefrontal cortex (PFC) using both retrograde transport of D-[ 3H]aspartate and electrophysiological approaches in the rat.  

The effects of stimulation of the substantia nigra pars reticulata (SNr) on the neurons of the mediodorsal nucleus (MD) projecting to the prefrontal cortex (PF) were studied in cats.  

The mediodorsal nucleus was the predominant source of projections to orbital areas, midline nuclei included consistently about 25% of the thalamic neurons directed to medial transitional cortices, and primary olfactory areas were distinguished by receiving thalamic projections predominantly from neurons in midline and intralaminar nuclei. Labeled neurons in the contralateral thalamus were noted in midline, the magnocellular sector of the mediodorsal nucleus, the anterior medial and intralaminar nuclei, and ranged from 0 to 14% of the ipsilateral; they were directed primarily to olfactory and transitional orbital and medial cortices but rarely projected to eulaminate areas.  

The L-IML lesion affects the mediodorsal nucleus (MDn) and both the intralaminar and paralaminar non-specific thalamic nuclei.  

These nuclei included the ventral lateral nucleus (VL), the intralaminar nuclei (ILN), the mediodorsal nucleus (MD) and midline nuclei.  

While patients with Wernicke's encephalopathy often had neuronal loss in the mediodorsal nucleus, only patients with Korsakoff's psychosis had cell loss in both medial thalamic nuclei.  

For example, generally no calcium-binding protein was detected in neurons of the anterodorsal, anteroventral, ventrolateral, ventral posterolateral, ventral posteromedial, or gelatinosus nuclei, or of the central part of the mediodorsal nucleus.  

Injections of these tracers were made into a variety of thalamic nuclei, including the intralaminar nuclei (most of these also involved the lateral part of the mediodorsal nucleus), the central part of the mediodorsal nucleus, the ventrolateral/ventromedial nuclei, and the ventral posterolateral/ventral posteromedial nuclei. Ascending reticular projections to the mediodorsal nucleus per se are somewhat weaker, while those to the ventrobasal complex (or at least the ventral posterolateral nucleus) are weaker still.  

To examine whether the striatal and thalamic connections from the prefrontal cortex arise from separate neuronal populations or are collateralized, two different fluorescent retrograde tracers (diamidino yellow and fast blue) were injected into topographically similar regions of the head of the caudate nucleus and the mediodorsal nucleus in the same animal. In contrast, the projections to the mediodorsal nucleus emanate largely from layer VI, and also from layer Vb. The differential laminar distributions of neurons projecting to the head of the caudate nucleus and the mediodorsal nucleus suggest that these structures may receive independent types of information from the prefrontal cortex..  

The thalamic projections of areas 24 and 32 were similar, but not identical, with projections to the mediodorsal nucleus (MD) and all of the midline nuclei.  

The VMCx also formed reciprocal connections with the ventrolateral, ventromedial and centrolateral nucleus, the lateral portion of the mediodorsal nucleus and the posterior complex of the thalamus.  

The most medial band included area 6-projecting neurons in the anterior nuclei, the rhomboid nucleus, the ventral anterior nucleus (VA), ventromedial nucleus (VM) and mediodorsal nucleus (MD).  

The organization of interconnections between the mediodorsal nucleus of the thalamus (MD) and the orbital and medial prefrontal cortex and the agranular insular cortex in the monkey was studied by retrograde and anterograde tracing techniques.  

The mediodorsal nucleus of thalamus represents a major efferent projection to the prefrontal cortex..  

The binding sites appeared to be confined to rat forebrain regions, e.g., orbital cortex, frontal cortex, cingulate cortex, piriform cortex, nucleus accumbens, amygdala, mediodorsal nucleus of the thalamus and arcuate and periventricular nuclei of the hypothalamus. Densitometric analysis of the autoradiographs revealed that the density of the binding sites was highest in the mediodorsal nucleus of the thalamus and the amygdala.  

Recordings were made in the frontal cortex and in various nuclei of the thalamus, in specific nuclei such as the ventroposterolateral, the ventroposteromedial and the ventrolateral nuclei, as well as in non-specific nuclei such as the mediodorsal nucleus, the reticular thalamic nucleus, the interanteromedial nucleus and the intralaminar nuclei (the central medial nucleus, the centrolateral nucleus and the paracentral nucleus). The activity in the specific nuclei and the mediodorsal nucleus shortly preceded the peak of the spike component.  

Following tritiated amino acid injections into the substantia nigra pars reticulata (SNr) and WGA-HRP injections into the contralateral cerebellar nuclei, we found that the nigrothalamic and cerebellothalamic afferents distribute to three main targets: the central portion of the ventral anterior nucleus (VA) and the ventral lateral nucleus (VL), the internal medullary lamina (IML) region, which includes the paralaminar VA, the mediodorsal nucleus (MD) and the central lateral nucleus (CL), and finally the ventromedial nucleus (VM).  

25-59% of LDTg neurones projecting to the mediodorsal nucleus provided collaterals to the midline nuclei.  

Other regions which receive sparse visual input include the lateral and anterior hypothalamic areas, the retrochiasmatic region, the sub-paraventricular zone, the paraventricular hypothalamic nucleus, the anteroventral and anterodorsal nuclei, the lateral habenula, the mediodorsal nucleus, and the basal telencephalon.(ABSTRACT TRUNCATED AT 400 WORDS).  

These results are interpreted in the context of recent evidence linking reversal learning to a neural network comprising the cholinergic basal forebrain, the amygdala and the orbitofrontal cortex, as well as the mediodorsal nucleus, and recent evidence of cholinergic deficits in this structure in patients with Alzheimer's disease..  

Significant potential changes were recorded in the mediodorsal nucleus of the thalamus and the lateral hypothalamic area. In the mediodorsal nucleus of the thalamus, the neurons responding to olfactory bulb electrical stimulation also responded to trigeminal nerve stimulation. These results suggest that olfactory and trigeminal pathways converge on the same neural elements within the mediodorsal nucleus of the thalamus and that the trigeminal input may modulate olfactory input in this nucleus..  

Deposits of somatopetal tracers, that filled the entire dorsolateral cortex of one hemisphere, labelled only a few cell bodies in the thalamic mediodorsal nucleus (MD).  

Numerical atrophy of neurons was found in the mediodorsal nucleus of the thalamus, amygdaloid nucleus, prefrontal cortex, impaired pattern of neuronal modules were found in the g.cinguli.  

Some intralaminar nuclei (central medial, central lateral, and paracentral), the reticular nucleus, midline nuclei (paraventricular and reuniens), some nuclei associated with the limbic system (anterodorsal nucleus and medially situated patches in the mediodorsal nucleus) and the lateral geniculate nucleus displayed the highest density of ChAT-positive axonal varicosities. The anterior intralaminar nuclei, the reticular nucleus, and medially situated patches in the mediodorsal nucleus displayed a substantial number of NGFr-positive varicose axons, presumably originating in the basal forebrain. While the vast majority of thalamic cholinergic input seems to come from the upper brainstem, the intralaminar and reticular nuclei, and especially medially situated patches within the mediodorsal nucleus also appear to receive substantial cholinergic innervation from the basal forebrain..  

Relatively sparse terminal fields associated with ascending fibers were also observed in the dorsomedial nucleus of the hypothalamus; in the nucleus reuniens, parataenial nucleus, paraventricular nucleus of the thalamus, and mediodorsal nucleus; in the central nucleus of the amygdala, anterodorsal part of the medial nucleus of the amygdala, posterior part of the basomedial nucleus of the amygdala; and in the ventral subiculum and adjacent parts of hippocampal field CA1, and the infralimbic and prelimbic areas of the medial prefrontal cortex.  

Mapping of the lesion demonstrated involvement of the caudal intralaminar nuclei (centre m├ędian and parafascicular nuclei), and portions of the medial nuclei (medioventral [ reuniens], centromedial, and the most inferior aspect of the mediodorsal nucleus). The majority of mediodorsal nucleus, the mammillary bodies, the mammillothalamic tract, and the anterior thalamic nuclei, were spared.  

In addition, neurons with CCK mRNA were found medially and laterally to the mediodorsal nucleus, in the midline and intralaminar nuclei.  

The medial and central segments of the mediodorsal nucleus of the thalamus (MD) receive afferents from the ventral forebrain, including the piriform cortex, the ventral pallidum, and the amygdaloid complex.  

Nine wide dynamic range neurons and two tap neurons were electrophysiologically identified and successfully stained with HRP in and around the parafascicular and subparafascicular nuclei, and in the mediodorsal nucleus.  

The distribution of presumptive glutamatergic and/or aspartatergic neurons retrogradely labeled following injections of 3HD-aspartate into the mediodorsal nucleus of the thalamus (MD) in the rat was compared to the distribution of neurons labeled by comparable injections of the nonspecific retrograde tracer wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP).  

Electrical stimulation of the mediodorsal nucleus (MD) of the thalamus elicited field potentials in the gyrus proreus (PRO), frontalis (FR), rectus (RE) and cinguli anterior (CIant) of the ipsilateral prefrontal and adjacent cortical areas in cats.  

The interconnected nuclei of the medial thalamus, most notably the mediodorsal nucleus, conversely appear to be associated with the development of the tachycardia that accompanies classical conditioning of the eyeblink and nictitating membrane response.  

The nigrothalamic label occupied a longitudinal band extending from rostral ventral anterior nucleus (VA) through to caudal mediodorsal nucleus (MD).  

The reactions of neurons of the associative mediodorsal nucleus of the thalamus to a solitary stimulation of the radial, sciatic, and splanchnic nerves were studied in conditions of an acute experiment in anesthetized and immobilized cats.  

The projections from the mediodorsal nucleus of the thalamus (MD) and the mesocortical dopaminergic (DA) projection were examined.  

The density of labeled terminals was especially high in the agranular insular cortex, olfactory tubercle, medial division of the mediodorsal nucleus of the thalamus, dorsal hypothalamic area and the lateral division of the central amygdaloid nucleus.  

The lateral geniculate nucleus, centrum medianum and mediodorsal nucleus were the first to be distinguished.  

Thus architectonically less differentiated medial and orbital prefrontal regions project to the medial sector of the mediodorsal nucleus, the magnocellular subdivision. In contrast, highly differentiated prefrontal area 8 projects to the most lateral sector of the mediodorsal nucleus, the multiformis subdivision. Lateral prefrontal areas with intermediate architectonic features project to the central parvocellular sector of the mediodorsal nucleus. Thus areas in the medial and dorsolateral cortices project to the dorsal part of the mediodorsal nucleus. In contrast, areas in orbital and ventrolateral cortices project to the ventral part of the mediodorsal nucleus. This successive and dichotomous organization of prefrontothalamic connections may provide the basis for the observed differential functions of the prefrontal cortex and the mediodorsal nucleus..  

The mediodorsal nucleus displayed a highly heterogeneous 5-HT innervation that varied from weak in its central portion to moderate or dense in its medial and lateral borders.  

In contrast, injections into the medial prefrontal cortex and mediodorsal nucleus of the thalamus resulted in dense anterograde and retrograde labeling primarily in the anterior agranular cortex, whereas injections in the amygdala resulted in axonal labeling in the agranular and dysgranular insular cortices. Our results indicate that ascending visceral afferents, VPLpc, VPMpc, and parabrachial nuclei, are topographically organized in the granular and dysgranular fields of the insular cortex, whereas the agranular cortex appears to receive highly integrated limbic afferents from the infralimbic cortex and the mediodorsal nucleus of the thalamus.  

In contrast to many other thalamic nuclei, cortical input to the mediodorsal nucleus arrives via two distinctive synaptic pathways, one terminating extraglomerularly and the other terminating within the synaptic glomeruli. The dual mode of corticothalamic terminations in the mediodorsal nucleus suggests a more potent and possibly different role for cortical input in the regulation of neuronal activity in this association nucleus than in sensory nuclei of the thalamus..  

Mediodorsal thalamic lesions including the medial part of the mediodorsal nucleus, similar to those which are frequently seen in Korsakoff amnesia, produced a severe impairment in this task.  

Medial area 6 is the target of afferents originating in a dorsolateral sector of the mediodorsal nucleus and in the ventroanterior nucleus. Medial prefrontal cortex is heavily innervated by pathways originating in the core of the mediodorsal nucleus and in the principal ventromedial nucleus.  

The labeling in mediodorsal nucleus following infralimbic cortex argues for including this area in the definition of rodent prefrontal cortex.  

Neurotensin-like immunoreactive (NTir) axon terminals in the mediodorsal nucleus of the thalamus (MD) in the adult rat were demonstrated by electron microscopic immunohistochemistry.  

Injections of two fluorescent retrograde tracers into the mediodorsal nucleus of the thalamus and the posterolateral hypothalamus showed that cells projecting to both diencephalic sites were intermingled in all of the olfactory cortical areas except the anterior olfactory nucleus, where cells were labeled only from the hypothalamus.  

The cholinergic innervation of the mediodorsal nucleus of the thalamus, which is thought to originate primarily in the laterodorsal tegmental nucleus and the substantia innominata, was studied by acetylcholinesterase histochemistry and immunohistochemistry with a polyclonal antiserum against human choline acetyltransferase on autopsy tissue from eight control subjects, five patients with progressive supranuclear palsy and four patients with senile dementia of Alzheimer type. In controls, cholinergic innervation of the mediodorsal nucleus of the thalamus was distributed heterogeneously in densely labelled patches surrounded by less heavily stained matrix. These results suggest that cholinergic innervation of mediodorsal nucleus matrix derives mainly from the laterodorsal tegmental nucleus and mediodorsal nucleus patches from the substantia innominata. Differential loss of innervation to the matrix and patches in progressive supranuclear palsy and senile dementia of Alzheimer type may in turn differentially affect mediodorsal nucleus innervation of the frontal cortex, resulting in dissimilar symptomatologies..  

The cortex of the upper bank of the STS-multimodal areas TPO and PGa-projects to four major thalamic targets: the pulvinar complex, the mediodorsal nucleus, the limitans-suprageniculate nucleus, as well as intralaminar nuclei.  

In addition, a parallel ascending pathway from the subpallidal area to the mediodorsal nucleus, and subsequently to the medial prefrontal cortex, probably mediates behaviour, e.g.  

Rabbits received ibotenic acid lesions of the mediodorsal nucleus of the thalamus (MD), or sham lesions.  

Rabbits received ibotenic acid lesions of the mediodorsal nucleus of the thalamus (MD) or sham lesions.  

Three groups of 3 monkeys received bilaterally symmetrical ablations in either the amygdala, the mediodorsal nucleus of the thalamus, or the ventromedial prefrontal cortex. One disconnection group had lesions in the amygdala and ventromedial prefrontal cortex; the other had lesions in the amygdala and the mediodorsal nucleus of the thalamus. Therefore, symmetrical bilateral lesions in either the amygdala, the mediodorsal nucleus, or the ventromedial prefrontal cortex produce similar impairments in the present task, implying that these structures are functionally related to each other; but the relatively mild effect of disconnecting these structures from each other argues against the hypothesis that they are serial stages in a single, tightly linked functional pathway..  

The anterior nuclear group and the mediodorsal nucleus showed high activities of ChAT and AChE together with relatively high levels of [ 3H]nicotine binding.  

The mediodorsal nucleus of the thalamus is known to be a source of afferents which terminate in layer IV of prefrontal cortex. However, combined retrograde transport and immunohistochemical techniques failed to reveal the presence of cholecystokinin-positive neurons in the mediodorsal nucleus of the thalamus that project to prefrontal cortex.  


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