Visuomotor control of locomotion and the effects of aging and stroke
Notice bibliographique
Résumé
Vision is arguably the most important sensory cue for the control of goal-directed locomotion. Optic flow, broadly defined as the pattern of light at the eye of a person moving through the environment, provides strong cues on the direction of locomotion, also known as heading. To date, most studies have only investigated the use of optic flow for heading in healthy young subjects. However, the capacity for visual processing can decline with advancing age or a neurological insult, such as stroke. These changes could impact on the control of heading and locomotion. The purpose of this thesis was to explore the role of optic flow in the control of locomotion in older adults and in stroke patients. In the first study, 2 groups of subjects (young: n=9, age 21.56 ± 3.20; old: n=9, age 66.11 ± 3.95) were instructed to walk straight in a virtual environment. As they progressed forward, the location from which the scene was expanding from, also know as the focus of expansion (FOE), was offset with a translation of 20° or 40° either to the left or right of the midline of the virtual scene. Young adults responded by displacing their centre of mass (CoM) mediolaterally in the direction opposite to the FOE shift, thus correcting their virtual trajectory so that they perceived walking straight in the virtual environment. In contrast, older adults showed very little trajectory corrections to the optic flow, resulting in large heading errors. In the second study, 10 young (age 23.49 ± 4.72) and 10 older adults (age 76.22 ± 3.11) were instructed to walk straight in a virtual environment where the FOE was gradually rotated until reaching 40° to the right or left at the end of the walking trial. Young adults displayed very small net heading errors in the virtual environment and responded by physically reorienting their heading and head in the direction opposite to the FOE rotation. Older adults showed similar responses, though they had smaller head rotations and slightly larger errors. Taken together, these 2 studies indicate that the effects of aging on the control of heading from optic flow are dependent on the type of flow presented and that the utilization of rotational flows while walking are less susceptible to aging than translational flows. In the third study, the same groups of healthy young and older adults (n=10 each) were tested on their ability to re-weight sensory information and maintain a straight heading in the physical environment while being exposed to rotational flows, as they walked at normal and fast walking speeds. Older participants made significantly larger heading errors than younger adults at normal walking speeds. Fast walking speed was found to improve the heading performance of young subjects but led to even larger heading errors in the older adults. This study suggests an increased reliance on visual cues for locomotor control in older adults who are less adept in visual reweighting. In the final study, a single-subject design was used to investigate the effects of stroke on the ability to use rotational optic flow cues while walking. Nine stroke patients were instructed to walk straight in a virtual environment with the FOE rotating 40° either towards the ipsilesional or contra-lesional side. Patterns of heading responses varied, with individuals having a history of neglect consistently showing heading larger errors than those without. The presence of persistent visuomotor deficits, particularly in far space, in stroke patients with a history of visuospatial neglect, is a novel finding of this thesis. In conclusion, central nervous system changes due to aging and stroke can impact the ability to use optic flow for the control of goal-directed locomotion. The underlying changes may pertain to the processing and/or integration of visual motion information.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
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 | 0,000 |
| 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 ».