Thalamocortical radiations

Résumé

In neuroanatomy, thalamocortical radiations also known as thalamocortical fibres, are the efferent fibres that project from the thalamus to distinct areas of the cerebral cortex. They form fibre bundles that emerge from the lateral surface of the thalamus. Structure Thalamocortical fibers (TC fibres) have been referred to as one of the two constituents of the isothalamus, the other being microneurons. Thalamocortical fibers have a bush or tree-like appearance as they extend into the internal capsule and project to the layers of the cortex. The main thalamocortical fibers extend from different nuclei of the thalamus and project to the visual cortex, somatosensory (and associated sensori-motor) cortex, and the auditory cortex in the brain. Thalamocortical radiations also innervate gustatory and olfactory pathways, as well as pre-frontal motor areas. Visual input from the optic tract is processed by the lateral geniculate nucleus of the thalamus, auditory input in the medial

Source officielle

https://en.wikipedia.org/wiki/Thalamocortical_radiations

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées (19)

Publications associées

Chargement

Personnes associées (3)

Personnes associées

Chargement

Unités associées (4)

Unités associées

Chargement

Concepts associés (9)

Le cortex cérébral (ou écorce cérébrale), d'origine prosencéphalique, est la substance grise périphérique des hémisphères cérébraux. Il se compose de trois couches (pour l'archi- et le paléocortex)

vignette|281x281px|Formation réticulée et posture La (ou ; également, en formatio reticularis) est une structure nerveuse du tronc cérébral à l'interface des systèmes autonome, moteur et sensitif. E

vignette|Vue tridimensionnelle du thalamus (en rouge). vignette|Thalamus (vue antérolatérale). vignette|Thalamus (vue supérieure). Le thalamus (du grec θάλαμος, chambre à coucher) est une structure

Afficher plus

Concepts associés

Chargement

Cours associés (2)

Cours associés

Chargement

Séances de cours associées (2)

Séances de cours associées

Chargement

A computational biophysical model of thalamic and reticular nucleus microcircuitry: from neurons to emergent network dynamics

Elisabetta Iavarone

The thalamus, once believed to be a simple relay station between the body periphery and the neocortex, has started to be recognized as a key player in higher-order functions, such as attention. It participates in the transition between brain states, such as sleep and wakefulness, and thalamocortical oscillations. Many of these functions involve the reticular nucleus (Rt), an inhibitory brain structure that surrounds the thalamus and where thalamocortical and corticothalamic axons establish synaptic contacts. Recent technical advances have made possible the study of thalamic activity in vivo and its contributions to cortical processing and behavior. However, a unified understanding of how network dynamics in the thalamus and the thalamocortical system is shaped by its neurons and synapses is still lacking. To address these challenges, we developed biophysically-detailed computational models of thalamic and reticular neurons. We then incorporated them in a large-scale model of thalamo-reticular microcircuitry, whose connectivity was directly constrained by three-dimensional reconstructions of neuronal morphologies. We included intrathalamic connections through chemical synapses, gap junctions and synapses from the sensory periphery and the neocortex. A large part of the data used to build and validate the model was extracted from the literature and leveraged a framework for its systematic and collaborative curation. This framework allowed us to keep track of parameter values used in the model, along with metadata describing the species, brain regions and experimental conditions. As a first validation of the model at the network level, we studied the generation of spindle-like oscillations. We found that external inputs are necessary to initiate this rhythm, while its termination can be sustained by the synaptic interplay alone, with a key role of mutual inhibition between reticular neurons. We found that that waxing-and-waning oscillations have a clear spatial component, that reflected the connectivity through chemical synapses as well as gap junctions. Finally, we investigated how differential depolarization in reticular and thalamocortical neurons influence the properties of spindle-like oscillations and predicted conditions where they are less easy to evoke. Taken together this thesis demonstrates how a bottom-up modelling approach can be successfully applied to reconstruct and simulate thalamic microcircuitry, which shows emergent network behavior compatible with experimental findings, and paves the way for understanding the role of the thalamus in thalamocortical functions.

EPFL2020

Chargement

Cortical afferents onto the nucleus Reticularis thalami promote plasticity of low-threshold excitability through GluN2C-NMDARs

Simone Astori, Gil Vantomme

Thalamus and cortex represent a highly integrated processing unit that elaborates sensory representations. Interposed between cortex and thalamus, the nucleus Reticularis thalami (nRt) receives strong cortical glutamatergic input and mediates top-down inhibitory feedback to thalamus. Despite growing appreciation that the nRt is integral for thalamocortical functions from sleep to attentional wakefulness, we still face considerable gaps in the synaptic bases for cortico-nRt communication and plastic regulation. Here, we examined modulation of nRt excitability by cortical synaptic drive in Ntsr1-Cre x ChR2(tg/+) mice expressing Channelrhodopsin2 in layer 6 corticothalamic cells. We found that cortico-nRt synapses express a major portion of NMDA receptors containing the GluN2C subunit (GluN2C-NMDARs). Upon repetitive photoactivation (10 Hz trains), GluN2C-NMDARs induced a long-term increase in nRt excitability involving a potentiated recruitment of T-type Ca2+ channels. In anaesthetized mice, analogous stimulation of cortical afferents onto nRt produced long-lasting changes in cortical local field potentials (LFPs), with delta oscillations being augmented at the expense of slow oscillations. This shift in LFP spectral composition was sensitive to NMDAR blockade in the nRt. Our data reveal a novel mechanism involving plastic modification of synaptically recruited T-type Ca2+ channels and nRt bursting and indicate a critical role for GluN2C-NMDARs in thalamocortical rhythmogenesis.

Nature Publishing Group2017

Chargement

In the mouse whisker system, sensory information is relayed to the whisker somatosensory cortex by two major thalamic nuclei, the ventral posterior medial nucleus (VPM) and the posterior medial nucleus (POM). While the cortical axonal innervation pattern of these two nuclei has been studied anatomically in some detail, their synaptic input to distinct cell-types across different layers in barrel cortex is incompletely understood. I used the specificity of optogenetics to selectively stimulate axons from VPM or POM, and I measured the evoked excitatory postsynaptic potentials in vitro with whole-cell patch-clamp recordings in primary whisker somatosensory cortex (wS1). VPM or POM was infected in vivo with an adenoassociated virus (AAV) encoding the light-gated cation channel channelrhodopsin (ChR2). Synaptic input onto individual neurons of the barrel cortex was recorded in brain slices in vitro by activating the ChR2-expressing thalamic axons with blue light. I measured thalamic inputs onto excitatory and three distinct classes of GABAergic neurons, expressing Parvalbumin (PV), somatostatin (SST) or vasoactive intestinal peptide (VIP) neurons across all layers of the barrel cortex. In excitatory and PV neurons, I found that the biggest inputs appeared to largely colocalize with the anatomical innervation pattern Anatomically, VPM preferentially innervates layer4 (L4), deep L3 and the L5B/6A border, and, functionally, we found that the biggest input was observed in L4, followed by L3. Anatomically, POM innervates L5A and L1, and, functionally, I found the biggest input in L5A. SST neurons received very weak input from both thalamic nuclei. VIP neurons on the other hand received larger inputs than SST neurons, however, they were weaker than excitatory and PV neurons. POM is considered to have both first-order and higher-order properties and I, therefore, began to investigate connectivity within sub-parts of POM. Taking advantage of a recently developed anterograde transsynaptic AAV injected into somatosensory brainstem nuclei, I defined first-order and higher-order sub-nuclei of POM and investigated their functional connectivity with somatosensory cortex. Anatomically, the first-order POM preferentially innervates L4 of the secondary somatosensory cortex (wS2) and functionally, I found that neurons across many layers in wS2 received direct synaptic input from first-order POM. Higher-order POM innervates both wS2 and wS1, and I found that neurons in wS2 also receive direct synaptic input. The data suggest that first-order POM relays sensory information to wS2, apparently in a parallel signaling pathway to the classical VPM to wS1 sensory pathway. In contrast, higher order POM does not appear to receive direct sensory input from the brainstem Our results begin to provide a more complete understanding of the distribution of thalamic input to specific cell-types across the layers of the mouse somatosensory cortex

EPFL2018

Chargement

A computational biophysical model of thalamic and reticular nucleus microcircuitry: from neurons to emergent network dynamics

Elisabetta Iavarone

EPFL2020

EPFL2018