Reorganization of auditory cortex in deaf people: functional, behavioural, and anatomical correlates
Notice bibliographique
Résumé
After early deafness, the brain can reorganize so that the sensory-deprived auditory cortex processes visual information. This cross-modal activity has been demonstrated numerous times in functional brain imaging research, but we still know little about the underlying mechanisms, the factors that constrain it, and its behavioural consequences. In this thesis, we address these unknowns in three studies that examine the functional, behavioural, and anatomical correlates of cross-modal reorganization in early-deaf adults. In study one, we used functional magnetic resonance imaging to identify cross-modal activity in the posterior superior temporal cortex of deaf people. With functional connectivity analysis, we explored the cortical network of this reorganized area and found enhanced interactions with primary visual cortex. Here, both the amplitude of the cross-modal activity and the strength of the audio-visual functional connectivity correlated with residual hearing, as measured by duration of hearing aid use: deaf people with more residual hearing showed less cross-modal reorganization. This study gives insight into the mechanism of cross-modal plasticity after deafness, revealing that it involves a network-level change and that it varies with the degree of auditory deprivation over the lifetime. In study two, we hypothesized that auditory deprivation causes compensatory changes to vision, and predicted that this would manifest as an improved ability in deaf people to detect visual motion. We designed a visual psychophysical test, which determined that people with early and profound deafness have lower motion detection thresholds than hearing controls. In study three, we followed up on the effect of study two, with the hypothesis that enhanced vision in deaf people is supported by cross-modal reorganization of auditory cortex. We measured cortical thickness with magnetic resonance imaging in early and profoundly deaf people, and found a correlation between visual motion detection thresholds and the thickness of the right posterior superior temporal cortex. This correlation implicates this area in compensatory vision and indicates an anatomical correlate – increased cortical thickness – of cross-modal plasticity. Based on the findings of these three studies, we conclude that cross-modal activity and increased cortical thickness in the right superior temporal cortex of deaf people reflect increased visual input to this area, and that these adaptations support enhanced visual motion detection, perhaps for sensory reorienting. We suggest that this plasticity may occur as a result of decreased activity-driven pruning after early auditory deprivation, and that it is interrupted when individuals exploit their residual hearing. This work illuminates the principles that govern cortical plasticity, and informs us on the organization and function of the right posterior superior temporal cortex.
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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 | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 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 ».