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Frontiers in Neural Circuits 2021The function of the higher-order sensory thalamus remains unclear. Here, the posterior medial (POm) nucleus of the thalamus was examined by extracellular recordings in...
The function of the higher-order sensory thalamus remains unclear. Here, the posterior medial (POm) nucleus of the thalamus was examined by extracellular recordings in anesthetized rats across a variety of contralateral, ipsilateral, and bilateral whisker sensory patterns. We found that POm was highly sensitive to multiwhisker stimuli involving diverse spatiotemporal interactions. Accurate increases in POm activity were produced during the overlapping time between spatial signals reflecting changes in the spatiotemporal structure of sensory patterns. In addition, our results showed for first time that POm was also able to respond to tactile stimulation of ipsilateral whiskers. This finding challenges the notion that the somatosensory thalamus only computes unilateral stimuli. We found that POm also integrates signals from both whisker pads and described how this integration is generated. Our results showed that ipsilateral activity reached one POm indirectly from the other POm and demonstrated a transmission of sensory activity between both nuclei through a functional POm-POm loop formed by thalamocortical, interhemispheric, and corticothalamic projections. The implication of different cortical areas was investigated revealing that S1 plays a central role in this POm-POm loop. Accordingly, the subcortical and cortical inputs allow POm but not the ventral posteromedial thalamic nucleus (VPM) to have sensory information from both sides of the body. This finding is in agreement with the higher-order nature of POm and can be considered to functionally differentiate and classify these thalamic nuclei. A possible functional role of these higher-order thalamic patterns of integrated activity in brain function is discussed.
Topics: Animals; Rats; Somatosensory Cortex; Thalamic Nuclei; Thalamus; Ventral Thalamic Nuclei; Vibrissae
PubMed: 34759802
DOI: 10.3389/fncir.2021.752804 -
Neurobiology of Disease Jan 2023Status epilepticus (SE) is a life-threatening emergency that can result in de novo development or worsening of epilepsy. We tested the hypothesis that the aberrant...
Status epilepticus (SE) is a life-threatening emergency that can result in de novo development or worsening of epilepsy. We tested the hypothesis that the aberrant cortical output during neocortical focal status epilepticus (FSE) would induce structural and functional changes in the thalamus that might contribute to hyperexcitability in the thalamocortical circuit. We induced neocortical FSE by unilateral epidural application of convulsant drugs to the somatosensory cortex of anesthetized mice of both sexes. The resulting focal EEG ictal episodes were associated with behavioral seizures consisting of contralateral focal myoclonic activity and persisted for 2-3 h. Ten and 30 days later, brains were processed for either immunohistochemistry (IHC) or in vitro slice recordings. Sections from the center of the thalamic reticular nucleus (nRT, see methods), the ventral posterolateral nucleus (VPL), and the ventral posteromedial nucleus (VPM) from the ventrobasal nucleus (VB) were used to measure density of NeuN-immunoreactive neurons, GFAP-reactive astrocytes, and colocalized areas for VGLUT1 + PSD95- and VGLUT2 + PSD95-IR, presumptive excitatory synapses of cortical and thalamic origins. Whole-cell voltage-clamp recordings were used to measure spontaneous EPSC frequency in these nuclei. We found that the nRT showed no decrease in numbers of neurons or evidence of reactive astrogliosis. In contrast, there were increases in GFAP-IR and decreased neuronal counts of NeuN positive cells in VB. Dual IHC for VGLUT1-PSD95 and VGLUT2-PSD95 in VB showed increased numbers of excitatory synapses, likely of both thalamic and cortical origins. The frequency, but not the amplitude of sEPSCs was increased in nRT and VB neurons. SIGNIFICANCE STATEMENT: Previous reports have shown that prolonged neocortical seizures can induce injury to downstream targets that might contribute to long-term consequences of FSE. Effects of FSE in thalamic structures may disrupt normal thalamo-cortical network functions and contribute to behavioral abnormalities and post-SE epileptogenesis. Our results show that a single episode of focal neocortical SE in vivo has chronic consequences including cell loss in VB nuclei and increased excitatory connectivity in intra-thalamic and cortico-thalamic networks. Additional experiments will assess the functional consequences of these alterations and approaches to mitigate cell loss and alterations in synaptic connectivity.
Topics: Male; Female; Mice; Animals; Neocortex; Thalamus; Neurons; Thalamic Nuclei; Seizures; Status Epilepticus
PubMed: 36442714
DOI: 10.1016/j.nbd.2022.105934 -
Brain and Behavior Jul 2022Trauma reexperiencing is dominated by recollection of sensory-perceptual elements of the trauma, pointing to involvement of the sensory thalamus. This study examined...
INTRODUCTION
Trauma reexperiencing is dominated by recollection of sensory-perceptual elements of the trauma, pointing to involvement of the sensory thalamus. This study examined posttraumatic stress symptoms in relation to volumes of thalamic nuclei that were grouped based on their predominant functions. We hypothesized that reexperiencing, controlling for other symptom dimensions, would correlate with volumes of thalamic nuclei involved in primary and higher-order sensory processing.
METHODS
Seventy-two trauma-exposed adults were interviewed with the Clinician Administered PTSD Scale for DSM-IV and underwent 3T magnetic resonance imaging. Scores were derived for reexperiencing, anxious arousal, dysphoric arousal, emotional numbing, and avoidance symptoms. These were entered as simultaneous predictors in five separate regression analyses, with age, sex, and total thalamus volume as covariates, predicting volumesf of five thalamus nuclear groupings corrected for intracranial volume: Specific sensory, associative-sensory, associative-cognitive, intralaminar, and motor groupings.
RESULTS
Reexperiencing symptoms were significantly positively correlated with volumes of the motor thalamic grouping, which included the ventral anterior, ventral lateral, and ventromedial nuclei. Anxious arousal was significantly negatively correlated with volumes of all five thalamic groupings.
CONCLUSIONS
Reexperiencing symptoms were correlated with volumes of the motor thalamus, while anxious arousal symptoms were related to all thalamic subregion volumes. Thalamic nuclei involved in motor functions, including oculomotor control and motor planning, may be implicated in posttraumatic reexperiencing symptoms.
Topics: Adult; Anxiety; Arousal; Humans; Stress Disorders, Post-Traumatic; Thalamic Nuclei; Thalamus
PubMed: 35676235
DOI: 10.1002/brb3.2639 -
NeuroImage Sep 2022The thalamus is a brain region formed from functionally distinct nuclei, which contribute in important ways to various cognitive processes. Yet, much of the human...
The thalamus is a brain region formed from functionally distinct nuclei, which contribute in important ways to various cognitive processes. Yet, much of the human neuroscience literature treats the thalamus as one homogeneous region, and consequently the unique contribution of specific nuclei to behaviour remains under-appreciated. This is likely due in part to the technical challenge of dissociating nuclei using conventional structural imaging approaches. Yet, multiple algorithms exist in the neuroimaging literature for the automated segmentation of thalamic nuclei. One recent approach developed by Iglesias and colleagues (2018) generates segmentations by applying a probabilistic atlas to subject-space anatomical images using the FreeSurfer software. Here, we systematically validate the efficacy of this segmentation approach in delineating thalamic nuclei using Human Connectome Project data. We provide several metrics quantifying the quality of segmentations relative to the Morel stereotaxic atlas, a widely accepted anatomical atlas based on cyto- and myeloarchitecture. The automated segmentation approach generated boundaries between the anterior, lateral, posterior, and medial divisions of the thalamus. Segmentation efficacy, as measured by metrics of dissimilarity (Average Hausdorff Distance) and overlap (DICE coefficient) within groups was mixed. Regions were better delineated in anterior, lateral and medial thalamus than the posterior thalamus, however all the volumes for all segmented nuclei were significantly different to the corresponding region of the Morel atlas. These mixed results suggest users should exercise care when using this approach to study the structural or functional relevance of a given thalamic nucleus.
Topics: Algorithms; Connectome; Humans; Imaging, Three-Dimensional; Magnetic Resonance Imaging; Thalamic Nuclei; Thalamus
PubMed: 35649466
DOI: 10.1016/j.neuroimage.2022.119340 -
Brain Structure & Function Mar 2023The thalamus plays an important role in the mediation and integration of various stimuli (e.g., somatosensory, pain, and vestibular). Whether a stimulus-specific and...
OBJECTIVES
The thalamus plays an important role in the mediation and integration of various stimuli (e.g., somatosensory, pain, and vestibular). Whether a stimulus-specific and topographic organization of the thalamic nuclei exists is still unknown. The aim of our study was to define a functional, in vivo map of multimodal sensory processing within the human thalamus.
METHODS
Twenty healthy individuals (10 women, 21-34 years old) participated. Defined sensory stimuli were applied to both hands (innocuous touch, mechanical pain, and heat pain) and the vestibular organ (galvanic stimulation) during 3 T functional MRI.
RESULTS
Bilateral thalamic activations could be detected for touch, mechanical pain, and vestibular stimulation within the left medio-dorsal and right anterior thalamus. Heat pain did not lead to thalamic activation at all. Stimuli applied to the left body side resulted in stronger activation patterns. Comparing an early with a late stimulation interval, the mentioned activation patterns were far more pronounced within the early stimulation interval.
CONCLUSIONS
The right anterior and ventral-anterior nucleus and the left medio-dorsal nucleus appear to be important for the processing of multimodal sensory information. In addition, galvanic stimulation is processed more laterally compared to mechanical pain. The observed changes in activity within the thalamic nuclei depending on the stimulation interval suggest that the stimuli are processed in a thalamic network rather than a distinct nucleus. In particular, the vestibular network within the thalamus recruits bilateral nuclei, rendering the thalamus an important integrative structure for vestibular function.
Topics: Humans; Female; Young Adult; Adult; Thalamus; Thalamic Nuclei; Pain; Ventral Thalamic Nuclei; Pain Perception
PubMed: 36239796
DOI: 10.1007/s00429-022-02582-y -
Trends in Neurosciences Jan 2000The pulvinar nuclei of the thalamus are proportionately larger in higher mammals, particularly in primates, and account for a quarter of the total mass. Traditionally,... (Review)
Review
The pulvinar nuclei of the thalamus are proportionately larger in higher mammals, particularly in primates, and account for a quarter of the total mass. Traditionally, these nuclei have been divided into oral (somatosensory), superior and inferior (both visual) and medial (visual, multi-sensory) divisions. With reciprocal connections to vast areas of cerebral cortex, and input from the colliculus and retina, they occupy an analogous position in the extra-striate visual system to the lateral geniculate nucleus in the primary visual pathway, but deal with higher-order visual and visuomotor transduction. With a renewed recent interest in this thalamic nuclear collection, and growth in our knowledge of the cortex with which it communicates, perhaps the time is right to look to new dimensions in the pulvinar code.
Topics: Animals; Behavior, Animal; Models, Neurological; Motor Cortex; Nerve Net; Primates; Pulvinar; Signal Transduction; Thalamic Nuclei; Vision, Ocular; Visual Pathways
PubMed: 10631787
DOI: 10.1016/s0166-2236(99)01482-4 -
Scientific Data Oct 2021Thalamic nuclei play critical roles in regulation of neurological functions like sleep and wakefulness. They are increasingly implicated in neurodegenerative and...
Thalamic nuclei play critical roles in regulation of neurological functions like sleep and wakefulness. They are increasingly implicated in neurodegenerative and neurological diseases such as multiple sclerosis and essential tremor. However, segmentation of thalamic nuclei is difficult due to their poor visibility in conventional MRI scans. Sophisticated methods have been proposed which require specialized MRI acquisitions and complex post processing. There are few high spatial resolution (1 mm or higher) in vivo MRI thalamic atlases available currently. The goal of this work is the development of an in vivo MRI-based structural thalamic atlas at 0.7 × 0.7 × 0.5 mm resolution based on manual segmentation of 9 healthy subjects using the Morel atlas as a guide. Using data analysis from healthy subjects as well as patients with multiple-sclerosis and essential tremor and at 3T and 7T MRI, we demonstrate the utility of this atlas to provide fast and accurate segmentation of thalamic nuclei when only conventional T weighted images are available.
Topics: Adult; Brain Mapping; Essential Tremor; Female; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Male; Multiple Sclerosis; Thalamic Nuclei; Young Adult
PubMed: 34711852
DOI: 10.1038/s41597-021-01062-y -
Magnetic Resonance Imaging Jun 2019Magnetic resonance imaging (MRI) is an important tool for analysis of deep brain grey matter structures. However, analysis of these structures is limited due to low...
Magnetic resonance imaging (MRI) is an important tool for analysis of deep brain grey matter structures. However, analysis of these structures is limited due to low intensity contrast typically found in whole brain imaging protocols. Herein, we propose a big data registration-enhancement (BDRE) technique to augment the contrast of deep brain structures using an efficient large-scale non-rigid registration strategy. Direct validation is problematic given a lack of ground truth data. Rather, we validate the usefulness and impact of BDRE for multi-atlas (MA) segmentation on two sets of structures of clinical interest: the thalamic nuclei and hippocampal subfields. The experimental design compares algorithms using T1-weighted 3 T MRI for both structures (and additional 7 T MRI for the thalamic nuclei) with an algorithm using BDRE. As baseline comparisons, a recent denoising (DN) technique and a super-resolution (SR) method are used to preprocess the original 3 T MRI. The performance of each MA segmentation is evaluated by the Dice similarity coefficient (DSC). BDRE significantly improves mean segmentation accuracy over all methods tested for both thalamic nuclei (3 T imaging: 9.1%; 7 T imaging: 15.6%; DN: 6.9%; SR: 16.2%) and hippocampal subfields (3 T T1 only: 8.7%; DN: 8.4%; SR: 8.6%). We also present DSC performance for each thalamic nucleus and hippocampal subfield and show that BDRE can help MA segmentation for individual thalamic nuclei and hippocampal subfields. This work will enable large-scale analysis of clinically relevant deep brain structures from commonly acquired T1 images.
Topics: Algorithms; Brain Mapping; Hippocampus; Humans; Image Enhancement; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Temporal Lobe; Thalamic Nuclei
PubMed: 30880111
DOI: 10.1016/j.mri.2019.03.014 -
The Journal of Headache and Pain Dec 2019The aim of this study is to investigate the alterations of thalamic nuclei volumes and the intrinsic thalamic network in patients with migraine.
BACKGROUND
The aim of this study is to investigate the alterations of thalamic nuclei volumes and the intrinsic thalamic network in patients with migraine.
METHODS
We enrolled 35 patients with migraine without aura and 40 healthy controls. All subjects underwent three-dimensional T1-weighted imaging. The thalamic nuclei were segmented using the FreeSurfer program. We investigated volume changes of individual thalamic nuclei and analyzed the alterations of the intrinsic thalamic network based on volumes in the patients with migraine.
RESULTS
Right and left thalamic volumes as a whole were not different between the patients with migraine and healthy controls. However, we found that right anteroventral and right and left medial geniculate nuclei volumes were significantly increased (0.00985% vs. 0.00864%, p = 0.0002; 0.00929% vs. 0.00823%, p = 0.0005; 0.00939% vs. 0.00769%, p < 0.0001; respectively) whereas right and left parafascicular nuclei volumes were decreased in the patients with migraine (0.00359% vs. 0.00435%, p < 0.0001; 0.00360% vs. 0.00438%, p < 0.0001; respectively) compared with healthy controls. The network measures of the intrinsic thalamic network were not different between the groups.
CONCLUSIONS
We found significant alterations of thalamic nuclei volumes in patients with migraine compared with healthy controls. These findings might contribute to the underlying pathogenesis of the migraine.
TRIAL REGISTRATION
None.
Topics: Adult; Cross-Sectional Studies; Female; Humans; Imaging, Three-Dimensional; Magnetic Resonance Imaging; Male; Middle Aged; Migraine Disorders; Organ Size; Prospective Studies; Thalamic Nuclei
PubMed: 31818256
DOI: 10.1186/s10194-019-1063-3 -
Neuroscience and Biobehavioral Reviews Jul 2015Lesions of the rodent anterior thalamic nuclei cause severe deficits to multiple spatial learning tasks. Possible explanations for these effects are examined, with... (Review)
Review
Lesions of the rodent anterior thalamic nuclei cause severe deficits to multiple spatial learning tasks. Possible explanations for these effects are examined, with particular reference to T-maze alternation. Anterior thalamic lesions not only impair allocentric place learning but also disrupt other spatial processes, including direction learning, path integration, and relative length discriminations, as well as aspects of nonspatial learning, e.g., temporal discriminations. Working memory tasks, such as T-maze alternation, appear particularly sensitive as they combine an array of these spatial and nonspatial demands. This sensitivity partly reflects the different functions supported by individual anterior thalamic nuclei, though it is argued that anterior thalamic lesion effects also arise from covert pathology in sites distal to the thalamus, most critically in the retrosplenial cortex and hippocampus. This two-level account, involving both local and distal lesion effects, explains the range and severity of the spatial deficits following anterior thalamic lesions. These findings highlight how the anterior thalamic nuclei form a key component in a series of interdependent systems that support multiple spatial functions.
Topics: Animals; Anterior Thalamic Nuclei; Cerebral Cortex; Hippocampus; Humans; Maze Learning; Mice; Nerve Net; Neural Pathways; Proto-Oncogene Proteins c-fos; Rats; Spatial Learning; Spatial Memory
PubMed: 25195980
DOI: 10.1016/j.neubiorev.2014.08.013