Plasticity following spinalization and step-training in the cat
Notice bibliographique
Résumé
Locomotot training has gained in popuiarity and is more and more integrated in tehabilitative strategies to enhance stepping recovery in spinal cord injured (SOI) individuals.This strategy is ditectly inspired from several decades of work performed in the Iaboratory taking advantage cf a spinal cat model in which reflex and locomotor pathways are exhaustively described.Compietely isclated from supraspinai influences, the spinal cord has the capacity to recover stepping movements when given repetitïve and appropriate sensory feedback related to step-training on a treadmill.However, the underlying mechanisms for recuperating the appropriate motor patterns are stiil poorly understood and are the scope of this study.Project I.It is generally assumed that plasticity in spinal locomotor circuits is responsible for the stepping recovery.However, the repetitive sensory stimulation related to step-training couid also modify transmission in reflex pathways, which are aise known to contribute significantly to the level cf muscle activity during stepping.In this project, transmission in reflex pathways was evaluated by measuring responses evoked by a stimulation cf a cutaneous or muscle nerve cf the hindpaw and recorded intracellularly in motoneurons from extensor and flexor muscles involved in ankle, knee and hip joint movements during an acute experiment in decerebrate cats.Possible modifications in reflex transmission were determined by the statistical comparison 0f responses between 2 groups cf spinal cats (complete transection at T13), but only one was assigned te a step-training regimen.Results showed that the synaptic transmission in both group I muscle reflex pathways from extensors and cutaneous pathways were modified following one month cf step-training.The monosynaptic excitation was decreased atter step-training and a normal pattern of modulation was recovered during locomotion.Moreover, group lb inhibition and polysynaptic group I excitation cf extensors were respectively decreased and increased after step-training and clonidine injection, a noradrenergic agonist useful for central pattern generation.t was further observed that plasticity in cutaneous pathways was highly specific: only certain pathways wete modulated (mostiy depressed).Transmission cf cutaneous input originating from the sole cf the foot was particularly modified.Overall, step-training is suggested te both decrease the hyperexcitability observed in reflex pathways after SCI and te facilitate the recruitment cf antigravity muscles te assist recovery and weight bearing.vi Project II.There is now strong evidence that spinal circuits can be affected by activity dependent biochemical processes that influence its ability to recover, perform and maintain an adequate Iocomotor pattern.Investigations have recentiy been oriented towatd molecules involved in LTP to determine if similar mechanisms are both implicated in hippocampal learning and spinal motor learning.Given the preponderant effect of ERK on synaptic piasticity and function and its role in integrating signais from the ceii surface to transcription factors, ERK appears to be a potentiai candidate for mediating the beneficial effects of step-training and may participate in the synaptic events associated with locomotor recovery aftet SOI.Ptotein expression was compared between 3 groups of cats (intact, SCI, SOI and step-trained) using western biot analysis of homogenates of spinal cord segments.The study focussed on assessing relative levels of ERK and pERK proteins.Resuits showed that ERK activation is up-regulated in a majority of lumbar segments following SCI and is specificaily down-reguiated in L5 by steptraining.These resuits suggest that ERK activation is invoived in long-term plasticity foilowing SOI and that it may be detrimental to iocomotor generation, at Ieast in specific spinal segments.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,004 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».