Early visual deprivation: strategies to prevent visual deficits and factors that promote recovery when deficits occur
Notice bibliographique
Résumé
The role of experience in the development of the central visual pathways has been a controversial issue that has been explored in the past through examination of the consequences of imposed periods of continuously abnormal visual input. I will report on a different approach whereby kittens were provided daily with separate periods of normal and abnormal visual exposure (Mitchell et al., 2003). For a period of 4 weeks beginning at 4 weeks of age, the total visual experience each day of kittens was restricted to 7 hours split unevenly between periods of monocular (ME) and binocular (BE) exposure. For the former exposure, the kittens wore an opaque mask that covered one eye for either 4 to 7 hrs while for the remaining time the mask was removed to allow binocular exposure. Visual acuity of the deprived eye for square-wave gratings was measured by use of a jumping stand immediately after termination of the 4 — week period of mixed visual exposure. The results indicated that two hours of normal binocular visual input each day allowed the development of normal visual acuity in both eyes even when imbedded in far longer periods of abnormal visual exposure that alone would lead to blindness in the deprived eye. The beneficial effects of BE were not observed in animals that wore dissociating prisms during the period when both eyes were open indicating that it was critical that the visual input to the two eyes be both simultaneous and concordant for visual acuity in the deprived eye to develop to normal levels. The results are not what would be expected by a passive process whereby neural connections are continually shaped in response to the integrated visual input during the sensitive period, but instead suggest a process which places greater weight on normal or certain preferred input that matches closely the anatomical and functional organization that develops prior to birth through programmed gene expression. In particular, concordant binocular visual input may be privileged with respect to its influence on visual development. On the other hand, changes to the visual pathway in response to visual input that favors one eye may require more extensive exposure because of the time necessary to mediate a different or more extensive set of synaptic or hetereocellular events than those that occur in response to concordant binocular input. A special role for binocular visual input was also observed in studies of the recovery from an early period of monocular deprivation. Although the resulting visual deficits in the deprived eye are reduced or eliminated by a period of reverse occlusion (analogous to patching therapy of human amblyopes), the improved vision in the deprived eye may not persist after the period of occlusion of the non-deprived eye is terminated. Moreover, the vision of the non-deprived eye may be permanently compromised as a result of occlusion. Experiments on animals that received periods of part-time occlusion of the non-deprived eye that allow a daily period of binocular visual exposure indicate a route by which deleterious effects of full-time occlusion can be avoided.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| 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 | 0,000 |
| 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) | 0,000 | 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 tête enseignante, 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 ».