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PubMed2000

A role for Pax6 in the normal development of dorsal thalamus and its cortical connections.

The transcription factor Pax6 is widely expressed throughout the developing nervous system, including most alar regions of the newly formed murine diencephalon. Later in embryogenesis its diencephalic expression becomes more restricted. It persists in the developing anterior thalamus (conventionally termed "ventral" thalamus) and pretectum but is downregulated in the body of the posterior (dorsal) thalamus. At the time of this downregulation, the dorsal thalamus forms its major axonal efferent pathway via the ventral telencephalon to the cerebral cortex. This pathway is absent in mice lacking functional Pax6 (small eye homozygotes: Sey/Sey). We tested whether the mechanism underlying this defect includes abnormalities of the dorsal thalamus itself. We exploited a new transgenic mouse ubiquitously expressing green fluorescent protein tagged with tau, in which axonal tracts are clearly visible, and co-cultured dorsal thalamic explants from Pax6(+/+ )or Pax6(Sey/Sey )embryos carrying the transgene with wild-type tissues from other regions of the forebrain. Whereas Pax6(+/+ )thalamic explants produced strong innervation of wild-type ventral telencephalic explants in a pattern that mimicked the thalamocortical tract in vivo, Pax6(Sey)(/Sey) explants did not, indicating a defect in the ability of mutant dorsal thalamic cells to respond to signals normally present in ventral telencephalon. Pax6(Sey)(/Sey) embryos also showed early alterations in the expression of regulatory genes in the region destined to become dorsal thalamus. Whereas in normal mice Nkx2.2 and Lim1/Lhx1 are expressed ventral to this region, in the mutants their expression domains are throughout it, suggesting that a primary action of Pax6 is to generate correct dorsoventral patterning in the diencephalon. Our results suggest that normal thalamocortical development requires the actions of Pax6 within the dorsal thalamus itself.

Alternative Splicing↗

PubMed2000

Functional connectivity in the thalamus and hippocampus studied with functional MR imaging.

BACKGROUND AND PURPOSE: With functional connectivity functional MR imaging, co-variance in signal intensity has been shown in functionally related regions of brain in participants instructed to perform no cognitive task. These changes are thought to represent synchronous fluctuations in blood flow, which imply neuronal connections between the regions. The purpose of this study was to map functional connectivity in subcortical nuclei with functional connectivity functional MR imaging. METHODS: Imaging data were acquired with an echo-planar sequence from six volunteers who performed no specific cognitive task. For functional connectivity functional MR imaging, a "seed" voxel or group of voxels was selected from the resting data set in the thalamus or in the hippocampus. Control voxels in gray matter presumed not to be eloquent cortex were also chosen. The correlation coefficient of the seed voxels and the control voxels with every other voxel in the resting data set was calculated. The voxels with correlation coefficients greater than or equal to 0.5 were mapped onto anatomic images for the functional connectivity functional MR images. The anatomic location of these voxels was determined by conventional parcellation methods. RESULTS: For each participant, functional connectivity functional MR imaging maps based on four seed voxels in the thalamus or hippocampus showed clusters of voxels in the ipsilateral and contralateral thalamus or hippocampus. For control voxels, few voxels in the hippocampus or thalamus showed significant correlation. Significantly more pixels in the ipsilateral hippocampus correlated with the seed voxel than in the contralateral hippocampus. The differences between numbers of functionally connected voxels in ipsilateral thalamus and those in contralateral thalamus were not significant. CONCLUSIONS: The thalamus and hippocampus show functional connectivity, presumably representing synchronous changes in blood flow.

Adult↗

PubMed1992

A comparison of the interaural time sensitivity of neurons in the inferior colliculus and thalamus of the unanesthetized rabbit.

The localization of low-frequency sounds (less than 3 kHz) along the azimuth involves comparing the ongoing difference in the time of arrival of a sound at the two ears. Information about interaural time differences (ITDs) is derived from an initial comparison performed in the superior olivary complex. However, little is known about which aspects of this information are transformed as it ascends the brainstem. To address this issue, we compared the ITD sensitivity of neurons in the inferior colliculus (IC) and auditory thalamus, successive stations in the auditory pathway. We found ITD sensitivity in the IC and thalamus to be similar in several respects. At both levels, the large majority of neurons responded maximally to ITDs within the range that a rabbit would normally encounter (+/- 300 microseconds) and preferred ipsilateral delays, delays that would be created by sounds in the contralateral sound field. The range of frequencies over which ITD sensitivity was expressed was also similar in the midbrain and thalamus. Several differences were also apparent. In comparison to IC neurons, neurons in the thalamus responded over more restricted ranges of ITD, responded at lower rates, and, in response to monaural stimulation, showed an increased influence of inhibition. Finally, a greater proportion of thalamic units had characteristic delays corresponding to intermediate discharge rates. The preservation of a bias for ipsilateral delays from IC to thalamus suggests that a representation of contralateral azimuths is present at both levels. Similarities between the two levels suggest that information about ITDs is faithfully transmitted from midbrain to thalamus. Differences in ITD sensitivity, such as the sharper tuning for ITDs, suggest that the thalamus is not a simple relay. Enhanced sensitivity to ITDs should translate to better-defined azimuthal receptive fields, and therefore may be a step toward achieving an optimal representation of azimuth within the auditory pathway.

Acoustic Stimulation↗

PubMedDate not supplied

[Neurofunctional aspects of the thalamus].

AIM: To carry out a revision of the principal neurofunctional aspects of the thalamus. DEVELOPMENT: Following the anatomical location of this cerebral structure in the diencephalon, we'll analyze the macroscopic characteristics of the thalamus establishing its anatomical limits. We'll study the main thalamic nuclei, taking into account different criteria: evolution, anatomical and functional, cytoarchitectonic, and connective fibers as well as the principal projections which reach and leave the thalamus, allowing an adequate information processing. The last part of this paper is dedicated to study of the aspects related with the participation of the thalamus in the basic psychofunctional processes and superior processes. CONCLUSIONS: The thalamus, in addition to its implication along with the cerebral cortex in the analysis and integration of sensitive and motor functions, is implied in superior functions like the attention, language, memory and executive function. The pulvinar nucleus, the lateral nuclear group and the anterior nuclear group take part in the language, fundamentally. In the mnesic processes, the scientific studies show that the midline nuclei, mediodorsal thalamic nuclei and intralaminar nuclei of the thalamus are implied in this superior function. Lesions of the thalamus can cause alterations in the executive functions, attention, initiative and temporal organization of the conduct. The mediodorsal nuclei, the intralaminar nuclei and the midline nuclei has been shown to have a critical role in executive function.

Emotions↗

PubMed1996

Specific innervation of the rat thalamus by grafted noradrenergic locus coeruleus neurons.

Growth and distribution of noradrenaline (NA) fibres from the implant into the thalamus of host rats were examined at 5-13 months after the implantation by immunohistochemistry using NA or tyrosine hydroxylase antisera. Cell suspension dissociated from the locus coeruleus (LC) region of 14-day-old rat fetuses was implanted into the center of the unilateral thalamus in adult rats from which the noradrenergic afferents to the thalamus had been eliminated with 6-hydroxydopamine treatment. A dense network of varicose NA-immunoreactive (NA-IR) fibres extended laterally into the posterior thalamic nuclear group and the ventral posterolateral thalamic nucleus from the implant in a pattern similar to that the intrinsic noradrenergic fibres form in the normal thalamus, i.e. laterally rich and medially poor NA fibres. Electron microscopic observations revealed that varicosities of NA-IR fibres formed symmetrical as well as asymmetrical axodendritic synapses and axo-axonic synapses with the host neurons as seen in the normal thalamus. labelled dendrite-like fibres of graft origin penetrated deep into the host brain and received afferents from non-labelled axon terminals. Varicosities of NA-IR fibres in the LC implanted animal formed axo-dendritic synapses at the higher ratio than those in the normal animal did. These results show that implanted fetal noradrenergic neurons innervate target regions of the thalamus specifically as the noradrenergic fibres in the normal thalamus do and maintain the innervation for a long time in the noradrenergically denervated rats.

Animals↗

PubMed2005

N-acetylaspartate reductions in the mediodorsal and anterior thalamus in men with schizophrenia verified by tissue volume corrected proton MRSI.

OBJECTIVE: Deficits in the mediodorsal and anterior nuclei of the thalamus may contribute to the psychopathological symptoms of schizophrenia. These thalamic nuclei have been found to be abnormal in schizophrenia and have close connections with other brain structures implicated in the disorder. We therefore examined schizophrenia-related alterations in brain metabolite levels specifically in the mediodorsal and anterior thalamic subregions. METHOD: We used in vivo proton magnetic resonance spectroscopic imaging ((1)H MRSI) to measure N-acetylaspartate (NAA), choline-containing compounds (Cho), and creatine+phosphocreatine (Cr) in the mediodorsal and anterior thalamus in 22 male patients with schizophrenia and 22 male controls. Magnetic resonance imaging (MRI) tissue segmentation and thalamic volume mask techniques were performed to distinguish the thalamus, extrathalamic gray and white matter, and CSF within the spectroscopic voxels. RESULTS: Compared to healthy subjects, patients with schizophrenia had significantly lower NAA in the mediodorsal and anterior thalamus bilaterally. No significant differences in Cho or Cr levels were seen. NAA was significantly higher in the left thalamus relative to the right in both groups. We found a strong negative correlation between left thalamic NAA and duration of illness, even after partialling out the effect of age. Tissue segmentation and thalamic volume mask techniques detected no group or lateralized differences in tissue type or CSF percentages, demonstrating that the metabolite reductions were not an artifact of spectroscopic voxel heterogeneity. CONCLUSIONS: These findings suggest diminished function and/or structure in the mediodorsal and anterior thalamus in male patients with schizophrenia and support earlier research demonstrating schizophrenia-related abnormalities in the thalamus and its circuitry.

Adult↗

PubMed2002

Reduced basal release of serotonin from the ventrobasal thalamus of the rat in a model of neuropathic pain.

Drugs that inhibit reuptake of monoamines are frequently used to treat pain syndromes, e.g. neuropathy or fibromyalgia, where mechanical allodynia is present. Several lines of evidence suggest the involvement of supraspinal sites of action of these drugs. However, a direct study of supraspinal serotonin (5-HT) or norepinephrine (NE) release in an animal model in which allodynia is expressed, e.g. neuropathy, has not been done. The ventrobasal (VB) thalamus and the hypothalamus are major supraspinal projection regions for spinal neurons that transmit nociceptive information and are innervated by monoaminergic fibers. This study determined if peripheral neuropathy would induce changes in extracellular monoamines in VB thalamus and hypothalamus. Male Sprague-Dawley rats had spinal nerve roots L5 and L6 tightly ligated (neuropathic rats; NP) or sham (SHAM) surgery; contralateral and ipsilateral VB thalamus and contralateral hypothalamus were dialyzed with modified artificial cerebral spinal fluid (aCSF), with and without fluoxetine. NP rats had significantly decreased 5-HT content in dialysates of the contralateral VB thalamus compared with SHAM rats with (82% decrease) or without (63% decrease) fluoxetine in the perfusion medium over the 180 min of the study. There were no differences in the ipsilateral VB thalamus. In contrast, release of 5-HT was unchanged in the hypothalamic dialysates of SHAM vs. NP rats. NE release was not different in dialysates of either the VB thalamus or hypothalamus of SHAM vs. NP rats. Synthesis of 5-HT, as assessed by accumulation of 5-hydroxytrytophan after treatment with an L-amino acid decarboxylase inhibitor, was not different between NP and SHAM rats in VB thalamic and hypothalamic brain tissue. This study is the first to demonstrate changes in monoamine release supraspinally in NP rats. The differential effect between VB thalamus and hypothalamus suggests that a terminal field change may be involved. Putative mechanisms for mediating this change include alterations of GABA-ergic systems and/or plasticity related to alterations in N-methyl-D-aspartate receptor activation and nitric oxide release related to afferent hyperactivity induced by neuropathic pain.

Animals↗

PubMed2005

Nociceptive stimulation activates locus coeruleus neurones projecting to the somatosensory thalamus in the rat.

In the thalamus, noradrenergic output from the pontine nucleus locus coeruleus (LC) may actively shape the response properties of various sensory networks en route to the cortex. Little is known, however, about the involvement of ascending noradrenergic innervation of the somatosensory thalamus in the processing of nociceptive information. To address this question, we combined the study of Fos expression upon nociceptive tooth pulp stimulation in the anaesthetized rat, with the detection of retrogradely traced neurones from the somatosensory thalamus. Cell bodies labelled retrogradely from the left thalamus were observed on both sides of the LC, with an ipsilateral predominance (n = 8). Electrical stimulation of the right incisor pulp (n = 4) provoked a significantly stronger Fos expression (around twice) than sham surgery (n = 4), in both the ipsi- and contralateral LC. Significantly larger numbers of double labelled neurones were counted in the LC of tooth-pulp-stimulated animals (representing around 30% of retrogradely labelled cells in LC) than in the LC of sham animals. They were found bilaterally, but with a clear, significant, ipsilateral (i.e. left) predominance. The present data offer an anatomical framework to understand how the LC is involved in the sensory processing of nociceptive information in the thalamus. For the first time, it is shown that nociceptive stimulation activates LC neurones projecting to the somatosensory thalamus. This suggests a new role for LC in modulating nociception within the thalamus.

Action Potentials↗

PubMed1989

A cyto-architectonic description of the thalamus of the tammar wallaby, Macropus eugenii.

Very few studies are available on the cyto-architectural features of the thalamus of metatherian mammals. Most of these studies describe the thalamus of a polyprotodont metatherian, the North American opossum, Didelphis virginiana. Studies on diprotodont metatherians are fewer still. There are two descriptions of the thalamus of the Australian possum Trichosurus vulpecula. The only part of the thalamus that has been described in the wallabies is the lateral geniculate nucleus. Hence, there was a need for a description of the thalamus in a wallaby. This study describes the organisation and the cyto-architectonics of the thalamus of the tammar, Macropus eugenii. Except for the midline nuclei, the boundaries of all other nuclei are well demarcated due to their well-differentiated nuclear components. Within the lateral posterior complex, a pulvinar nucleus was identified, and the pre-tectal nuclei show extensive differentiation, as do the medial geniculate nuclei. Also, a small centre-median nucleus was identified. The anteroventral nucleus retains its dorsal position for its entire rostrocaudal extent. The nucleus of the optic tract is located in a dorsal position in the tammar, as it is in cats. The general conclusion from this study is that the nuclear organisation of the thalamus in the tammar, a metatherian mammal, is complex and comparable in most respects to that in cats, eutherian mammals.

Animals↗

PubMed1999

Connections between cells of the internal capsule, thalamus, and cerebral cortex in embryonic rat.

The aim of our study is to understand the development of the earliest connections in the mammalian pallium by documenting the distribution of cells and fibres labelled from the dorsal and ventral thalamus, internal capsule, perirhinal, and dorsal cortex during the period between embryonic day (E) 14 and 17 by using carbocyanine dye tracing in fixed embryonic rat brains. Dye placed in the thalamus of E14 brains backlabels cells in the thalamic reticular nucleus and within the primitive internal capsule. Both anterograde and retrograde tracing confirmed that the first corticofugal projections reach the internal capsule by E14. At E15-E16, after the first cortical plate cells have migrated into the lateral cortex, some cells of the cortical plate and subplate and marginal zone, are backlabelled from the internal capsule, but still not from the dorsal thalamus, even with very long incubation periods. Crystal placement into the perirhinal cortex at E14-E15 labels numerous cells within the internal capsule, whereas no such cells are revealed from dorsal cerebral cortex until E17, suggesting that internal capsule cells establish early connections with the perirhinal and ventral but not dorsal cortex. We propose that the growth of axons from cortex to dorsal thalamus is delayed in two regions: first from E14-E15 at the lateral entrance of the internal capsule and then, from E16, closer to the thalamus, probably within the thalamic reticular nucleus. Subplate projections reach the proximity of the diencephalon at an early stage, but they might never enter the dorsal thalamus.

Animals↗

PubMed1994

Movement disorders following lesions of the thalamus or subthalamic region.

Reports of 62 cases with a movement disorder associated with a focal lesion in the thalamus and/or subthalamic region were analyzed. Thirty-three cases had a lesion confined to the thalamus. Sixteen cases had a thalamic lesion extending into the subthalamic region and/or midbrain. Thirteen cases had a lesion in the subthalamic region or a subthalamic lesion extending into the midbrain. Nineteen cases with dystonia, 18 with asterixis, 17 with ballism-chorea, three with paroxysmal dystonia, and five with clonic or myorhythmic movements have been described. No case with isolated tremor has been described. In 53 cases with unilateral thalamic or subthalamic lesions, all but one with bilateral blepharospasm (associated with right posterior thalamic, pontomesencephalic, and bilateral cerebellar lesions) had dyskinesias in the limbs contralateral to the lesion. The other nine cases had bilateral paramedian thalamic lesions; seven developed bilateral dyskinesias, and the remaining two had unilateral dyskinesias. Regarding the 19 patients with dystonia, the two with bilateral blepharospasm had thalamic and upper brainstem lesions, and one with hemidystonia and torticollis had a subthalamic lesion. The other 16 patients all had a unilateral thalamic lesion with contralateral dystonia (10 hemidystonia, five focal dystonia affecting a hand and/or and one segmental dystonia involving face, arm, and hand). The exact location of the thalamic lesion was mentioned in 10 cases; the posterior or posterolateral thalamus was involved in six and the paramedian thalamus in four. These areas are more posterior or medial to the ventrolateral and ventroanterior thalamic nuclei, which receive pallido-thalamic and nigro-thalamic afferents. Two cases developed dystonia immediately after thalamotomy, and one case developed it 4 days after head trauma. The others initially had a hemiplegia and developed dystonia 1-9 months after the acute insult. Fifteen of the 17 patients with chorea had a unilateral lesion in the subthalamic nucleus or subthalamic region (eight due to infarcts, one to hemorrhage, five to mass lesions, and one to multiple sclerosis). All had contralateral hemichorea or hemiballism. One other case had bilateral chorea of the hands and tongue due to paramedian thalamic infarction. Another case with generalized chorea and thalamic atrophy was complicated by stereotaxic surgery. Thirteen of the 18 cases with asterixis had lesions confined to the thalamus. Eight were associated with thalamotomy, and five others had a stroke (four infarction and one hemorrhage) affecting the contralateral thalamus.(ABSTRACT TRUNCATED AT 400 WORDS)

Dominance, Cerebral↗

PubMed1988

Transient asymmetry in the projections of the rostral thalamus to the visual hyperstriatum of the chicken, and reversal of its direction by light exposure.

Asymmetry in the visual pathways from the rostral thalamus to the hyperstriatum of the chicken has been found after injecting the retrograde tracer, True Blue (TB), into either the left or right hyperstriatum on day 2 or 12, post-hatching. There are ipsilateral connections from the ventromedial region of the left dorsolateral thalamus, lateral part (DLL) to the left hyperstriatum, and contralateral connections from the left dorsolateral thalamus, rostrolateral part (DLAlr) and the dorsolateral thalamus, dorsal part (DLLd) to the right hyperstriatum. On the right side of the thalamus, the ipsilateral connections from DLL to the right hyperstriatum are present, but there are only very few contralateral connections to the left hyperstriatum. No asymmetry in these pathways is seen in animals injected with TB on day 21. By this age the contralateral connections from the right thalamus to the left hyperstriatum have developed. Thus, the structural asymmetry in these visual pathways is transient, a finding which explains a controversy between two papers published recently in this journal, and which adds considerably to our understanding of the behavioural asymmetries known to occur in the chicken's response to stimuli presented to either the left or right eye. The direction of the asymmetry in visual pathways depends on asymmetrical light input to the eyes of the embryo. Normally the head of the embryo is oriented such that the left eye is occluded. If the head is withdrawn from the egg so that the right eye can be occluded and the left eye exposed to light, the direction of asymmetry in the thalamo-hyperstriatal pathways is reversed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Evidence for a projection from the perireticular thalamic nucleus to the dorsal thalamus in the adult rat and ferret.

During early development, the perireticular thalamic nucleus is very large (i.e. has many cells) and has a strong projection to the dorsal thalamus and to the cerebral neocortex. By adulthood, the nucleus has much reduced in size and only a few cells remain. It is not clear whether these perireticular cells that remain into adulthood maintain their connections with the dorsal thalamus and with the neocortex. This study examines this issue by injecting neuronal tracers into various nuclei of the dorsal thalamus (dorsal lateral geniculate nucleus, medial geniculate complex, ventroposteromedial nucleus, lateral posterior nucleus, posterior thalamic nucleus) and into different areas of the neocortex (somatosensory, visual, auditory). After injections of tracer into the individual nuclei of the rat and ferret dorsal thalamus, retrogradely-labelled perireticular cells are seen. In general, after each injection, the retrogradely-labelled perireticular cells lie immediately adjacent to a group of retrogradely-labelled reticular cells. For instance, after injections into the medial geniculate complex, perireticular cells adjacent to the auditory reticular sector are retrogradely-labelled, whilst after an injection into the dorsal lateral geniculate nucleus, retrogradely-labelled perireticular cells adjacent to the visual reticular sector are seen. By contrast, injections of tracer into various areas of the rat and ferret neocortex result in no retrogradely-labelled cells in the perireticular nucleus. Thus, unlike during perinatal development when perireticular cells project to both neocortex and dorsal thalamus, perireticular cells in the adult seem to project to the dorsal thalamus only: the perireticular projection to the neocortex appears to be entirely transient.

Animals↗

PubMed1998

Neuronal activity in the monkey ventrolateral thalamus following perturbations of voluntary wrist movements.

Extracellular single-cell recordings were made from the cerebellar thalamus (89 neurones) and the VPLc (53 neurones) of three conscious monkeys. The animals were trained to perform wrist movement paradigms including: (a) visually triggered skilled, voluntary movements; (b) 100-ms duration torque pulse perturbations applied during a hold period (termed Pa perturbations); (c) 100-ms perturbations that commenced 100 ms after the visual trigger but during preparation before a skilled, voluntary movement (termed Pb perturbations); and (d) 100-ms perturbations during the skilled, voluntary movement (termed Pm perturbations). These Pb and Pm perturbations were used to identify central and peripheral influences on patterns of neuronal discharge in the ventrolateral thalamus. There was no systematic difference between the responses to Pb and Pm perturbations of neurones in the cerebellar thalamus and those in VPLc. The responses of VPLc and cerebellar thalamic neurones to Pa perturbations were considered to represent transduction of peripheral afferent input, and these responses were compared with the responses to the other types of perturbations. Up to 40% of neurones in cerebellar thalamus and VPLc responded to Pb and Pm perturbations in a similar pattern to that which followed Pa perturbations, and therefore most likely represented faithful transduction of peripheral input. However, the response of over half the neurones in VPLc and cerebellar thalamus to Pb or Pm perturbations differed from Pa perturbations in a manner suggesting that central influences had gated the peripheral input. The short-latency response in cerebellar thalamus which was modified by central influences is appropriately timed to contribute to the "intended" response to perturbations of motor cortical neurones.

Afferent Pathways↗

PubMed1987

Importance of bilateral sympathetic innervation on cerebral blood flow autoregulation in the thalamus.

Effects of bilateral sympathetic innervation on the regulation of cerebral blood flow to the thalamus were examined in spontaneously hypertensive rats (SHR). The superior cervical ganglion was removed on one side or bilaterally, and blood flow in the thalamus was repeatedly measured with a hydrogen clearance technique during a stepwise increase in arterial pressure. Regional blood flow in the thalamus was unchanged following acute ganglionectomy: 55 +/- 6 ml/100 g/min in the intact rats and 56 +/- 4 in the denervated rats. Sympathectomy on one side neither had effects on the pressure-flow relationship nor on the blood pressure levels of upper limits of autoregulation in the ipsilateral thalamus. In contrast, bilateral sympathetic denervation impaired the autoregulatory function in the thalamus and the upper limits were significantly lower than those in intact rats: 206 +/- 8 vs 226 +/- 10 mm Hg, respectively (P less than 0.02). It is concluded that overlapping innervation of sympathetic nerves has an important role in regulation of blood flow to the thalamus during an acute rise in arterial pressure in SHR.

Adrenergic Fibers↗

PubMed2026

Large-Scale Neuroimaging and Genetic Analyses of the Human Thalamus in Loneliness.

BACKGROUND: Although loneliness is prevalent and significantly impacts society globally, its neural and genetic bases remain poorly understood. The thalamus, which receives sensory information from the environment, may have a more significant role in social interactions than previously recognized. Here, we integrate neuroimaging and genetic approaches to characterize structural differences within the thalamus associated with loneliness. METHODS: We obtained thalamic nuclei volumes on brain scans from 45,834 individuals (age range: 45-82 years) in the UK Biobank and grouped them into 6 anatomical groups. We investigated effects of loneliness and social isolation using self-reported data. Then, we performed a genome-wide association study (GWAS) analysis on the genetic overlap between thalamic volumes and loneliness. RESULTS: The volumes of the whole thalamus and its medial, lateral, and posterior nuclei are significantly reduced in individuals with loneliness compared with those who do not feel lonely. Loneliness with frequent social contact is associated with smaller volumes, whereas social isolation without loneliness shows no such reduction in thalamus volumes. Leveraging data from GWASs on thalamic volumes (n = 30,114) and loneliness (n = 370,342) in the UK Biobank, we identified shared loci between thalamus structure and loneliness. CONCLUSIONS: Our findings support the emerging view that the thalamus plays important roles in social interactions and in the experience of loneliness.

Genetic architecture↗

PubMed2000

Proton spectroscopic imaging of the thalamus in treatment-naive pediatric obsessive-compulsive disorder.

BACKGROUND: Neurobiological abnormalities in the thalamus, particularly the dorsomedial nucleus of the thalamus, are believed to be involved in the pathophysiology of obsessive-compulsive disorder. Although obsessive-compulsive disorder commonly arises in childhood and adolescence, no prior study has examined the thalamus in pediatric obsessive-compulsive disorder patients. METHODS: In this study, N-acetyl-aspartate, a putative marker of neuronal viability, creatine/phosphocreatine, and choline levels were measured in the lateral and medical subregions of the left and right thalami using a multislice proton magnetic resonance spectroscopic imaging sequence in 11 treatment-naive, nondepressed obsessive-compulsive disorder outpatients, 8-15 years old, and 11 case-matched control subjects. RESULTS: A significant reduction in N-acetyl-aspartate/choline and N-acetyl-aspartate/(creatine/phosphocreatine + choline) was observed in both the right and left medial thalami in obsessive-compulsive disorder patients compared with control subjects. The N-acetyl-aspartate/choline and N-acetyl-aspartate/(creatine/phosphocreatine + choline) levels did not differ significantly between case-control pairs in either the left or the right lateral thalamus. Reduction in N-acetyl-aspartate levels in the left medial thalamus was inversely correlated with increased obsessive-compulsive disorder symptom severity. CONCLUSIONS: These findings provide new evidence of localized functional neurochemical marker abnormalities in the thalamus in pediatric obsessive-compulsive disorder. Our results must be considered preliminary, however, given the small sample size.

Adolescent↗

PubMed1998

Destruction of the auditory thalamus disrupts the production of fear but not the inhibition of fear conditioned to an auditory stimulus.

The auditory thalamus is part of a neural circuit that mediates the expression of fear to auditory stimuli. Bilateral lesions of the auditory thalamus prevent the expression of fear to an auditory stimulus paired with shock. The present study assessed whether bilateral lesions of the auditory thalamus would also disrupt the inhibition of fear to an auditory stimulus paired with the absence of shock. Rats were given bilateral lesions of the auditory thalamus followed by Pavlovian conditioned inhibition training in which a light was paired with shock and a noise and light compound was presented in the absence of shock. Fear and the inhibition of fear were measured with the fear-potentiated startle effect. Lesions of the auditory thalamus did not disrupt the ability of the noise to inhibit the expression of fear to the light. However, these lesions did disrupt the ability of the noise to produce fear-potentiated startle after it had been subsequently paired with shock. These results suggest that although the auditory thalamus is an essential part of a neural circuit that mediates the expression of fear to auditory stimuli, it is not an essential part of the circuit that mediates the inhibition of fear to auditory stimuli.

Acoustic Stimulation↗